Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries

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Neukom, R.; Grosjean, M.; Wanner, H. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), Bern (Switzerland); University of Bern, Institute of Geography, Climatology and Meteorology, Bern (Switzerland); Luterbacher, J. [Justus Liebig University of Giessen, Department of Geography, Climatology, Climate Dynamics and Climate Change, Giessen (Germany); Villalba, R.; Morales, M.; Srur, A. [CONICET, Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales (IANIGLA), Mendoza (Argentina); Kuettel, M. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), Bern (Switzerland); University of Bern, Institute of Geography, Climatology and Meteorology, Bern (Switzerland); University of Washington, Department of Earth and Space Sciences, Seattle (United States); Frank, D. [Swiss Federal Research Institute WSL, Birmensdorf (Switzerland); Jones, P.D. [University of East Anglia, Climatic Research Unit, School of Environmental Sciences, Norwich (United Kingdom); Aravena, J.-C. [Centro de Estudios Cuaternarios de Fuego Patagonia y Antartica (CEQUA), Punta Arenas (Chile); Black, D.E. [Stony Brook University, School of Marine and Atmospheric Sciences, Stony Brook (United States); Christie, D.A.; Urrutia, R. [Universidad Austral de Chile Valdivia, Laboratorio de Dendrocronologia, Facultad de Ciencias Forestales y Recursos Naturales, Valdivia (Chile); D' Arrigo, R. [Earth Institute at Columbia University, Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Palisades, NY (United States); Lara, A. [Universidad Austral de Chile Valdivia, Laboratorio de Dendrocronologia, Facultad de Ciencias Forestales y Recursos Naturales, Valdivia (Chile); Nucleo Cientifico Milenio FORECOS, Fundacion FORECOS, Valdivia (Chile); Soliz-Gamboa, C. [Utrecht Univ., Inst. of Environmental Biology, Utrecht (Netherlands); Gunten, L. von [Univ. of Bern (Switzerland); Univ. of Massachusetts, Climate System Research Center, Amherst (United States)

2011-07-15

We statistically reconstruct austral summer (winter) surface air temperature fields back to ad 900 (1706) using 22 (20) annually resolved predictors from natural and human archives from southern South America (SSA). This represents the first regional-scale climate field reconstruction for parts of the Southern Hemisphere at this high temporal resolution. We apply three different reconstruction techniques: multivariate principal component regression, composite plus scaling, and regularized expectation maximization. There is generally good agreement between the results of the three methods on interannual and decadal timescales. The field reconstructions allow us to describe differences and similarities in the temperature evolution of different sub-regions of SSA. The reconstructed SSA mean summer temperatures between 900 and 1350 are mostly above the 1901-1995 climatology. After 1350, we reconstruct a sharp transition to colder conditions, which last until approximately 1700. The summers in the eighteenth century are relatively warm with a subsequent cold relapse peaking around 1850. In the twentieth century, summer temperatures reach conditions similar to earlier warm periods. The winter temperatures in the eighteenth and nineteenth centuries were mostly below the twentieth century average. The uncertainties of our reconstructions are generally largest in the eastern lowlands of SSA, where the coverage with proxy data is poorest. Verifications with independent summer temperature proxies and instrumental measurements suggest that the interannual and multi-decadal variations of SSA temperatures are well captured by our reconstructions. This new dataset can be used for data/model comparison and data assimilation as well as for detection and attribution studies at sub-continental scales. (orig.)

Spatio-temporal variability of Arctic summer temperatures over the past 2 millennia

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Werner, Johannes P.; Divine, Dmitry V.; Charpentier Ljungqvist, Fredrik; Nilsen, Tine; Francus, Pierre

2018-04-01

In this article, the first spatially resolved and millennium-length summer (June-August) temperature reconstruction over the Arctic and sub-Arctic domain (north of 60° N) is presented. It is based on a set of 44 annually dated temperature-sensitive proxy archives of various types from the revised PAGES2k database supplemented with six new recently updated proxy records. As a major advance, an extension of the Bayesian BARCAST climate field (CF) reconstruction technique provides a means to treat climate archives with dating uncertainties. This results not only in a more precise reconstruction but additionally enables joint probabilistic constraints to be imposed on the chronologies of the used archives. The new seasonal CF reconstruction for the Arctic region can be shown to be skilful for the majority of the terrestrial nodes. The decrease in the proxy data density back in time, however, limits the analyses in the spatial domain to the period after 750 CE, while the spatially averaged reconstruction covers the entire time interval of 1-2002 CE.The centennial to millennial evolution of the reconstructed temperature is in good agreement with a general pattern that was inferred in recent studies for the Arctic and its subregions. In particular, the reconstruction shows a pronounced Medieval Climate Anomaly (MCA; here ca. 920-1060 CE), which was characterised by a sequence of extremely warm decades over the whole domain. The medieval warming was followed by a gradual cooling into the Little Ice Age (LIA), with 1766-1865 CE as the longest centennial-scale cold period, culminating around 1811-1820 CE for most of the target region.In total over 600 independent realisations of the temperature CF were generated. As showcased for local and regional trends and temperature anomalies, operating in a probabilistic framework directly results in comprehensive uncertainty estimates, even for complex analyses. For the presented multi-scale trend analysis, for example, the spread in

The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland.

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Birgander, Johanna; Olsson, Pål Axel; Rousk, Johannes

2018-01-18

Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm-tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years' winter warming. The warming treatments increased winter soil temperatures by 5-6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q 10 ) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat-spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil-atmosphere C

Spatio-temporal variability of Arctic summer temperatures over the past 2 millennia

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J. P. Werner

2018-04-01

Full Text Available In this article, the first spatially resolved and millennium-length summer (June–August temperature reconstruction over the Arctic and sub-Arctic domain (north of 60° N is presented. It is based on a set of 44 annually dated temperature-sensitive proxy archives of various types from the revised PAGES2k database supplemented with six new recently updated proxy records. As a major advance, an extension of the Bayesian BARCAST climate field (CF reconstruction technique provides a means to treat climate archives with dating uncertainties. This results not only in a more precise reconstruction but additionally enables joint probabilistic constraints to be imposed on the chronologies of the used archives. The new seasonal CF reconstruction for the Arctic region can be shown to be skilful for the majority of the terrestrial nodes. The decrease in the proxy data density back in time, however, limits the analyses in the spatial domain to the period after 750 CE, while the spatially averaged reconstruction covers the entire time interval of 1–2002 CE.The centennial to millennial evolution of the reconstructed temperature is in good agreement with a general pattern that was inferred in recent studies for the Arctic and its subregions. In particular, the reconstruction shows a pronounced Medieval Climate Anomaly (MCA; here ca. 920–1060 CE, which was characterised by a sequence of extremely warm decades over the whole domain. The medieval warming was followed by a gradual cooling into the Little Ice Age (LIA, with 1766–1865 CE as the longest centennial-scale cold period, culminating around 1811–1820 CE for most of the target region.In total over 600 independent realisations of the temperature CF were generated. As showcased for local and regional trends and temperature anomalies, operating in a probabilistic framework directly results in comprehensive uncertainty estimates, even for complex analyses. For the presented multi

A pollen-based reconstruction of summer temperature in central North America and implications for circulation patterns during medieval times

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Wahl, Eugene R.; Diaz, Henry F.; Ohlwein, Christian

2012-03-01

We present a reconstruction of mean summer temperature for the northern Midwest of the USA based on lacustrine pollen records from three different lakes in Wisconsin. The results suggest a relatively warm period during the earlier part of the record (~ 1200-1500 CE) followed by a cooler Little Ice Age (~ 1500-1900) and a subsequent warming to modern conditions. The reconstructed modern summer mean temperature is in good agreement with observations, and the decades of the 1930s to 1950s appear to be the warmest such period in the proxy record (through 1974). Analyses of circulation features associated with the warmest summers in the recent climate record suggest a prevalence of continental ridging accompanied by generally dry conditions during these warm summers in the Midwest. Drought reconstruction using the Palmer Drought Severity Index (PDSI) and tree-ring records as predictors also yield relatively dry conditions in medieval times for the central US. As reported in a number of recent studies, possible forcing mechanisms include La Niña-like conditions in the equatorial Pacific and warmer than average waters in the tropical Indo-western Pacific Ocean possibly coupled to a positive mode of the AMO/NAO North Atlantic circulation pattern.

The Impact of “Unseasonably” Warm Spring Temperatures on Acute Myocardial Infarction Hospital Admissions in Melbourne, Australia: A City with a Temperate Climate

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Margaret Loughnan

2014-01-01

Full Text Available The effects of extreme temperatures on human health have been well described. However, the adverse health effects of warm weather that occurs outside the summer period have had little attention. We used daily anomalous AMI morbidity and daily anomalous temperature to determine the impact of “unseasonable” temperature on human health. The “unseasonably” warm weather was attributed to a slow moving high pressure system to the east of Melbourne. No morbidity displacement was noted during either of these periods suggesting that morbidity due to “unseasonable” temperatures is avoidable. An increase in warmer weather during the cooler months of spring may result in increased morbidity, and an alert system based on summer thresholds may not be appropriate for early season heat health warnings. A straightforward alert system based on calculating anomalous temperature from daily weather forecasts may reduce the public health impact of “unseasonably” warm weather.

Parasitic copepod (Lernaea cyprinacea) outbreaks in foothill yellow-legged frogs (Rana boylii) linked to unusually warm summers in northern California

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Sarah J. Kupferberg; Alessandro Catenazzi; Kevin Lunde; Amy J. Lind; Wendy J. Palen

2009-01-01

How climate change may affect parasite–host assemblages and emerging infectious diseases is an important question in amphibian decline research. We present data supporting a link between periods of unusually warm summer water temperatures during 2006 and 2008 in a northern California river, outbreaks of the parasitic copepod Lernaea cyprinacea, and...

Cold climate bioventing with soil warming in Alaska

International Nuclear Information System (INIS)

Sayles, G.D.; Brenner, R.C.; Leeson, A.; Hinchee, R.E.; Vogel, C.M.

1995-01-01

In the heart of Alaska, a 3-year field study was conducted of bioventing in conjunction with several soil warming methods. The contamination was JP-4 jet fuel. The soil warming methods evaluated, chosen for their apparent low cost, were (1) application of warm water at a low rate, (2) enhanced solar warming by covering the surface with clear plastic in the summer and covering the surface with insulation in the winter, and (3) buried heat pipe. The warm water and buried heat tape methods performed best, maintaining summer-like 10 to 20 C temperatures in the test plots year round, compared to the temperature of the unheated control plot, which dipped to -1 C in the winter. The solar/insulation warming method showed a modest improvement in temperature over the unheated control test plot. The annual average temperatures of the warm water, heat tape, solar, and control plots were 16.9, 14.5, 6.1, and 3.5 C, respectively. The biodegradation rates, measured by in situ respirometry, were higher in plots with higher temperatures and followed the Arrhenius relationship. Despite the low temperature, significant biodegradation was observed in the unheated plot during the winter

The impact of future summer temperature on public health in Barcelona and Catalonia, Spain

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Ostro, Bart; Barrera-Gómez, Jose; Ballester, Joan; Basagaña, Xavier; Sunyer, Jordi

2012-11-01

Several epidemiological studies have reported associations between increases in summer temperatures and risks of premature mortality. The quantitative implications of predicted future increases in summer temperature, however, have not been extensively characterized. We have quantified these effects for the four main cities in Catalonia, Spain (Barcelona, Tarragona, Lleida, Girona). We first used case-crossover analysis to estimate the association between temperature and mortality for each of these cities for the period 1983 to 2006. These exposure-response (ER) functions were then combined with local measures of current and projected changes in population, mortality and temperature for the years 2025 and 2050. Predicted daily mean temperatures were based on the A1B greenhouse gas emission, "business-as-usual" scenario simulations derived from the ENSEMBLES project. Several different ER functions were examined and significant associations between temperature and mortality were observed for all four cities. For these four cities, the age-specific piecewise linear model predicts 520 (95%CI 340, 720) additional annual deaths attributable to the change in temperature in 2025 relative to the average from the baseline period of 1960-1990. For 2050, the estimate increases to 1,610 deaths per year during the warm season. For Catalonia as a whole, the point estimates for those two years are 720 and 2,330 deaths per year, respectively, or about 2 and 3% of the warm season. In comparing these predicted impacts with current causes of mortality, they clearly represent significant burdens to public health in Catalonia.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme hot summer

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Tachibana, Yoshihiro; Otomi, Yuriko; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

Science.gov (United States)

Otomi, Yuriko; Tachibana, Yoshihiro; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

Atmospheric Dynamics Leading to West European Summer Hot Temperatures Since 1851

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M. Carmen Alvarez-Castro

2018-01-01

Full Text Available Summer hot temperatures have many impacts on health, economy (agriculture, energy, and transports, and ecosystems. In Western Europe, the recent summers of 2003 and 2015 were exceptionally warm. Many studies have shown that the genesis of the major heat events of the last decades was linked to anticyclonic atmospheric circulation and to spring precipitation deficit in Southern Europe. Such results were obtained for the second part of the 20th century and projections into the 21st century. In this paper, we challenge this vision by investigating the earlier part of the 20th century from an ensemble of 20CR reanalyses. We propose an innovative description of Western-European heat events applying the dynamical system theory. We argue that the atmospheric circulation patterns leading to the most intense heat events have changed during the last century. We also show that the increasing temperature trend during major heatwaves is encountered during episodes of Scandinavian Blocking, while other circulation patterns do not yield temperature trends during extremes.

Rising Mediterranean Sea Surface Temperatures Amplify Extreme Summer Precipitation in Central Europe

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Volosciuk, Claudia; Maraun, Douglas; Semenov, Vladimir A.; Tilinina, Natalia; Gulev, Sergey K.; Latif, Mojib

2016-08-01

The beginning of the 21st century was marked by a number of severe summer floods in Central Europe associated with extreme precipitation (e.g., Elbe 2002, Oder 2010 and Danube 2013). Extratropical storms, known as Vb-cyclones, cause summer extreme precipitation events over Central Europe and can thus lead to such floodings. Vb-cyclones develop over the Mediterranean Sea, which itself strongly warmed during recent decades. Here we investigate the influence of increased Mediterranean Sea surface temperature (SST) on extreme precipitation events in Central Europe. To this end, we carry out atmosphere model simulations forced by average Mediterranean SSTs during 1970-1999 and 2000-2012. Extreme precipitation events occurring on average every 20 summers in the warmer-SST-simulation (2000-2012) amplify along the Vb-cyclone track compared to those in the colder-SST-simulation (1970-1999), on average by 17% in Central Europe. The largest increase is located southeast of maximum precipitation for both simulated heavy events and historical Vb-events. The responsible physical mechanism is increased evaporation from and enhanced atmospheric moisture content over the Mediterranean Sea. The excess in precipitable water is transported from the Mediterranean Sea to Central Europe causing stronger precipitation extremes over that region. Our findings suggest that Mediterranean Sea surface warming amplifies Central European precipitation extremes.

Strong impacts of daily minimum temperature on the green-up date and summer greenness of the Tibetan Plateau.

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Shen, Miaogen; Piao, Shilong; Chen, Xiaoqiu; An, Shuai; Fu, Yongshuo H; Wang, Shiping; Cong, Nan; Janssens, Ivan A

2016-09-01

Understanding vegetation responses to climate change on the Tibetan Plateau (TP) helps in elucidating the land-atmosphere energy exchange, which affects air mass movement over and around the TP. Although the TP is one of the world's most sensitive regions in terms of climatic warming, little is known about how the vegetation responds. Here, we focus on how spring phenology and summertime greenness respond to the asymmetric warming, that is, stronger warming during nighttime than during daytime. Using both in situ and satellite observations, we found that vegetation green-up date showed a stronger negative partial correlation with daily minimum temperature (Tmin ) than with maximum temperature (Tmax ) before the growing season ('preseason' henceforth). Summer vegetation greenness was strongly positively correlated with summer Tmin , but negatively with Tmax . A 1-K increase in preseason Tmin advanced green-up date by 4 days (P greenness by 3.6% relative to the mean greenness during 2000-2004 (P green-up date (P > 0.10) and higher summer Tmax even reduced greenness by 2.6% K(-1) (P greenness were probably due to the accompanying decline in water availability. The dominant enhancing effect of nighttime warming indicates that climatic warming will probably have stronger impact on TP ecosystems than on apparently similar Arctic ecosystems where vegetation is controlled mainly by Tmax . Our results are crucial for future improvements of dynamic vegetation models embedded in the Earth System Models which are being used to describe the behavior of the Asian monsoon. The results are significant because the state of the vegetation on the TP plays an important role in steering the monsoon. © 2016 John Wiley & Sons Ltd.

Inter-Relationship Between Subtropical Pacific Sea Surface Temperature, Arctic Sea Ice Concentration, and the North Atlantic Oscillation in Recent Summers and Winters

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Lim, Young-Kwon; Cullather, Richard I.; Nowicki, Sophie M.; Kim, Kyu-Myong

2017-01-01

The inter-relationship between subtropical western-central Pacific sea surface temperatures (STWCPSST), sea ice concentration in the Beaufort Sea (SICBS), and the North Atlantic Oscillation (NAO) are investigated for the last 37 summers and winters (1980-2016). Lag-correlation of the STWCPSST×(-1) in spring with the NAO phase and SICBS in summer increases over the last two decades, reaching r = 0.4-0.5 with significance at 5 percent, while winter has strong correlations in approximately 1985-2005. Observational analysis and the atmospheric general circulation model experiments both suggest that STWCPSST warming acts to increase the Arctic geopotential height and temperature in the following season. This atmospheric response extends to Greenland, providing favorable conditions for developing the negative phase of the NAO. SIC and surface albedo tend to decrease over the Beaufort Sea in summer, linked to the positive surface net shortwave flux. Energy balance considering radiative and turbulent fluxes reveal that available energy that can heat surface is larger over the Arctic and Greenland and smaller over the south of Greenland, in response to the STWCPSST warming in spring. XXXX Arctic & Atlantic: Positive upper-level height/T anomaly over the Arctic and Greenland, and a negative anomaly over the central-eastern Atlantic, resembling the (-) phase of the NAO. Pacific: The negative height/T anomaly over the mid-latitudes, along with the positive anomaly over the STWCP, where 1degC warming above climatology is prescribed. Discussion: It is likely that the Arctic gets warm and the NAO is in the negative phase in response to the STWCP warming. But, there are other factors (e.g., internal variability) that contribute to determination of the NAO phase: not always the negative phase of the NAO in the event of STWCP warming (e.g.: recent winters and near neutral NAO in 2017 summer).

Causes and consequences of past and projected Scandinavian summer temperatures, 500-2100 AD.

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Ulf Büntgen

Full Text Available Tree rings dominate millennium-long temperature reconstructions and many records originate from Scandinavia, an area for which the relative roles of external forcing and internal variation on climatic changes are, however, not yet fully understood. Here we compile 1,179 series of maximum latewood density measurements from 25 conifer sites in northern Scandinavia, establish a suite of 36 subset chronologies, and analyse their climate signal. A new reconstruction for the 1483-2006 period correlates at 0.80 with June-August temperatures back to 1860. Summer cooling during the early 17th century and peak warming in the 1930s translate into a decadal amplitude of 2.9°C, which agrees with existing Scandinavian tree-ring proxies. Climate model simulations reveal similar amounts of mid to low frequency variability, suggesting that internal ocean-atmosphere feedbacks likely influenced Scandinavian temperatures more than external forcing. Projected 21st century warming under the SRES A2 scenario would, however, exceed the reconstructed temperature envelope of the past 1,500 years.

Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long term context

Czech Academy of Sciences Publication Activity Database

Wilson, R.; Anchukaitis, K.; Briffa, K. R.; Büntgen, Ulf; Cook, E.; D'Arrigo, R.; Davi, N.; Esper, J.; Frank, D.; Gunnarson, B.; Hegerl, G.; Helama, S.; Klesse, S.; Krusic, P. J.; Linderholm, H. W.; Myglan, V. S.; Osborn, T. J.; Rydval, M.; Schneider, L.; Schurer, A.; Wiles, G.; Zhang, P.; Zorita, E.

2016-01-01

Roč. 134, FEB (2016), s. 1-18 ISSN 0277-3791 Institutional support: RVO:67179843 Keywords : high-resolution paleoclimatology * stable carbon isotopes * medieval warm period * past 600 years * blue intensity * volcanic-eruptions * density data * ice-age * dendroclimatic reconstruction * cambium phenology * Tree-rings * Northern hemisphere * Last millennium * Summer temperatures * Reconstruction * CMIP5 models Subject RIV: EH - Ecology, Behaviour Impact factor: 4.797, year: 2016

Local warming: daily temperature change influences belief in global warming.

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Li, Ye; Johnson, Eric J; Zaval, Lisa

2011-04-01

Although people are quite aware of global warming, their beliefs about it may be malleable; specifically, their beliefs may be constructed in response to questions about global warming. Beliefs may reflect irrelevant but salient information, such as the current day's temperature. This replacement of a more complex, less easily accessed judgment with a simple, more accessible one is known as attribute substitution. In three studies, we asked residents of the United States and Australia to report their opinions about global warming and whether the temperature on the day of the study was warmer or cooler than usual. Respondents who thought that day was warmer than usual believed more in and had greater concern about global warming than did respondents who thought that day was colder than usual. They also donated more money to a global-warming charity if they thought that day seemed warmer than usual. We used instrumental variable regression to rule out some alternative explanations.

Atmospheric Circulation Patterns over East Asia and Their Connection with Summer Precipitation and Surface Air Temperature in Eastern China during 1961-2013

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Li, Shuping; Hou, Wei; Feng, Guolin

2018-04-01

Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961-2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in eastern China as well as associated external forcing are investigated. Three patterns of the atmospheric circulation are identified, all with quasi-barotropic structures: (1) the East Asia/Pacific (EAP) pattern, (2) the Baikal Lake/Okhotsk Sea (BLOS) pattern, and (3) the eastern China/northern Okhotsk Sea (ECNOS) pattern. The positive EAP pattern significantly increases precipitation over the Yangtze River valley and favors cooling north of the Yangtze River and warming south of the Yangtze River in summer. The warm sea surface temperature anomalies over the tropical Indian Ocean suppress convection over the northwestern subtropical Pacific through the Ekman divergence induced by a Kelvin wave and excite the EAP pattern. The positive BLOS pattern is associated with below-average precipitation south of the Yangtze River and robust cooling over northeastern China. This pattern is triggered by anomalous spring sea ice concentration in the northern Barents Sea. The anomalous sea ice concentration contributes to a Rossby wave activity flux originating from the Greenland Sea, which propagates eastward to North Pacific. The positive ECNOS pattern leads to below-average precipitation and significant warming over northeastern China in summer. The reduced soil moisture associated with the earlier spring snowmelt enhances surface warming over Mongolia and northeastern China and the later spring snowmelt leads to surface cooling over Far East in summer, both of which are responsible for the formation of the ECNOS pattern.

Climatic change of summer temperature and precipitation in the Alpine region - a statistical-dynamical assessment

Energy Technology Data Exchange (ETDEWEB)

Heimann, D.; Sept, V.

1998-12-01

Climatic changes in the Alpine region due to increasing greenhouse gas concentrations are assessed by using statistical-dynamical downscaling. The downscaling procedure is applied to two 30-year periods (1971-2000 and 2071-2100, summer months only) of the output of a transient coupled ocean/atmosphere climate scenario simulation. The downscaling results for the present-day climate are in sufficient agreement with observations. The estimated regional climate change during the next 100 years shows a general warming. The mean summer temperatures increase by about 3 to more than 5 Kelvin. The most intense climatic warming is predicted in the western parts of the Alps. The amount of summer precipitation decreases in most parts of central Europe by more than 20 percent. Only over the Adriatic area and parts of eastern central Europe an increase in precipitation is simulated. The results are compared with observed trends and results of regional climate change simulations of other authors. The observed trends and the majority of the simulated trends agree with our results. However, there are also climate change estimates which completely contradict with ours. (orig.) 29 refs.

Why tropical forest lizards are vulnerable to climate warming

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Huey, Raymond B.; Deutsch, Curtis A.; Tewksbury, Joshua J.; Vitt, Laurie J.; Hertz, Paul E.; Álvarez Pérez, Héctor J.; Garland, Theodore

2009-01-01

Biological impacts of climate warming are predicted to increase with latitude, paralleling increases in warming. However, the magnitude of impacts depends not only on the degree of warming but also on the number of species at risk, their physiological sensitivity to warming and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of warming because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are warm all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of warm temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that warming will not only further depress their physiological performance in summer, but will also enable warm-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key components of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate warming, even though rates of tropical warming may be relatively low. PMID:19324762

Seasonal variations in methane fluxes in response to summer warming and leaf litter addition in a subarctic heath ecosystem

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Pedersen, Emily Pickering; Elberling, Bo; Michelsen, Anders

2017-08-01

Methane (CH4) is a powerful greenhouse gas controlled by both biotic and abiotic processes. Few studies have investigated CH4 fluxes in subarctic heath ecosystems, and climate change-induced shifts in CH4 flux and the overall carbon budget are therefore largely unknown. Hence, there is an urgent need for long-term in situ experiments allowing for the study of ecosystem processes over time scales relevant to environmental change. Here we present in situ CH4 and CO2 flux measurements from a wet heath ecosystem in northern Sweden subjected to 16 years of manipulations, including summer warming with open-top chambers, birch leaf litter addition, and the combination thereof. Throughout the snow-free season, the ecosystem was a net sink of CH4 and CO2 (CH4 -0.27 mg C m-2 d-1; net ecosystem exchange -1827 mg C m-2 d-1), with highest CH4 uptake rates (-0.70 mg C m-2 d-1) during fall. Warming enhanced net CO2 flux, while net CH4 flux was governed by soil moisture. Litter addition and the combination with warming significantly increased CH4 uptake rates, explained by a pronounced soil drying effect of up to 32% relative to ambient conditions. Both warming and litter addition also increased the seasonal average concentration of dissolved organic carbon in the soil. The site was a carbon sink with a net uptake of 60 g C m-2 over the snow-free season. However, warming reduced net carbon uptake by 77%, suggesting that this ecosystem type might shift from snow-free season sink to source with increasing summer temperatures.

Impact of the Atlantic Warm Pool on precipitation and temperature in Florida during North Atlantic cold spells

Energy Technology Data Exchange (ETDEWEB)

Donders, Timme H. [Utrecht University, Laboratory of Palaeobotany and Palynology, Institute of Environmental Biology, Utrecht (Netherlands); TNO Geological Survey of the Netherlands, Utrecht (Netherlands); Boer, Hugo Jan de; Dekker, Stefan C. [Utrecht University, Department of Environmental Sciences, Faculty of Geosciences, P.O. Box 80115, Utrecht (Netherlands); Finsinger, Walter; Wagner-Cremer, Friederike [Utrecht University, Laboratory of Palaeobotany and Palynology, Institute of Environmental Biology, Utrecht (Netherlands); Grimm, Eric C. [Research and Collections Center, Illinois State Museum, Springfield, IL (United States); Reichart, Gert Jan [Utrecht University, Geochemistry, Department of Earth Sciences, Faculty of Geosciences, P.O. Box 80021, Utrecht (Netherlands)

2011-01-15

Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong stadials terminated by so-called Heinrich events. The climatic significance of these pine phases has been interpreted in different ways. Using a pollen-climate inference model, we quantified the climate changes and consistently found that mean summer precipitation (P{sub JJA}) increased (0.5-0.9 mm/day) and mean November temperature increased (2.0-3.0 C) during pine phases coeval with Heinrich events and the Younger Dryas. Marine sea surface temperature records indicate that potential sources for these moisture and heat anomalies are in the Gulf of Mexico and the western tropical Atlantic. We explain this low latitude warming by an increased Loop Current facilitated by persistence of the Atlantic Warm Pool during summer. This hypothesis is supported by a climate model sensitivity analysis. A positive heat anomaly in the Gulf of Mexico and equatorial Atlantic best approximates the pollen-inferred climate reconstructions from Lake Tulane during the (stadials around) Heinrich events and the Younger Dryas. (orig.)

Observed changes in seasonal heat waves and warm temperature extremes in the Romanian Carpathians

Science.gov (United States)

Micu, Dana; Birsan, Marius-Victor; Dumitrescu, Alexandru; Cheval, Sorin

2015-04-01

Extreme high temperature have a large impact on environment and human activities, especially in high elevation areas particularly sensitive to the recent climate warming. The climate of the Romanian Carpathians became warmer particularly in winter, spring and summer, exibiting a significant increasing frequency of warm extremes. The paper investigates the seasonal changes in the frequency, duration and intensity of heat waves in relation to the shifts in the daily distribution of maximum temperatures over a 50-year period of meteorological observations (1961-2010). The paper uses the heat wave definition recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI) and exploits the gridded daily dataset of maximum temperature at 0.1° resolution (~10 km) developed in the framework of the CarpatClim project (www.carpatclim.eu). The seasonal changes in heat waves behavior were identified using the Mann-Kendall non-parametric trend test. The results suggest an increase in heat wave frequency and a lengthening of intervals affected by warm temperature extremes all over the study region, which are explained by the shifts in the upper (extreme) tail of the daily maximum temperature distribution in most seasons. The trends are consistent across the region and are well correlated to the positive phases of the East Atlantic Oscillation. Our results are in good agreement with the previous temperature-related studies concerning the Carpathian region. This study was realized within the framework of the project GENCLIM, financed by UEFISCDI, code PN-II 151/2014.

Summer Temperature Extremes in the Northern Rockies: A Tree-Ring-Based Reconstruction (1670-2014) from the Bighorn Mountains, WY

Science.gov (United States)

Hudson, A.; Alfaro-Sanchez, R.; Belmecheri, S.; Moore, D. J.; Trouet, V.

2017-12-01

Anthropogenic climate change has caused global temperatures to rise in recent decades. Temperatures at the regional scale are influenced by various factors including topography, atmospheric circulation, and seasonality that superimpose year-to-year variability on this global warming trend. Here, we develop a tree-ring based summer temperature reconstruction for the northern Rockies in order to investigate the drivers of the year-to-year temperature variability in this region. For this purpose, we sampled 10 sites in the semi-arid Bighorn Mountains, WY and developed two tree-ring width chronologies for differing elevations. The high elevation Picea engelmannii chronology (>2,630m) is positively correlated with July temperature variability, whereas the low elevation (<2,580m) chronology - consisting of Pinus contorta, Pseudotsuga menziesii, and Pinus albicaulis - is sensitive to summer precipitation and negatively correlated with June and July temperatures. A reconstruction based on a combination of the two chronologies explains 30% of the variance in regional June and July temperatures over the instrumental period, covers the period 1670-2014, and is representative for the central United States and southern Canada region. Our reconstruction shows significantly lower summer temperatures in the year following the 16 largest tropical eruptions from 1670 to the present. The reconstruction further captures the high summer temperatures during the 1930s dust bowl era and shows a steep increase in variance in the late 20th century. Enhanced late 20th century variance has also been detected in climate and ecosystem dynamics in the Northeast Pacific, which suggests an impact of an amplified meridional flow on northern Rockies summer temperatures.

The sensitivity of the Indian summer monsoon to a global warming of 2 C with respect to pre-industrial times

Energy Technology Data Exchange (ETDEWEB)

May, Wilhelm [Danish Meteorological Institute, Danish Climate Centre, Copenhagen (Denmark)

2011-11-15

lower (upper) level in the Indian region. The comparison with the changes in the Indian summer monsoon associated with a global warming of 4.5 C reveals that both the intensification of the monsoon precipitation and the weakening of the large-scale monsoon circulation (particularly in the lower troposphere) are relatively strong (with respect to the magnitude of the projected global warming by the end of the twentieth century for the two scenarios) in the scenario with a global warming of 2 C. The relatively strong intensification of the monsoon rainfall is related to rather strong increases in evaporation over the Arabian Sea and the Bay of Bengal, while a rather weak amplification of the meridional temperature gradient between the Indian Ocean and the land areas to the north contributes to the relatively strong reduction of the large-scale monsoon flow. (orig.)

The response of East Asian Summer Monsoon to a Global Warming Scenario

Science.gov (United States)

Stan, C.; Jin, Y.

2016-12-01

The response of East Asian Summer Monsoon (EASM) to the abrupt quadrupling of atmospheric CO2 concentration is investigated using the Super-Parameterized Community Climate Model, version 4 (SP-CCSM4). The EASM precipitation and circulation intensify in response to global warming and these changes are related to the westward extension of the Western North Pacific Subtropical High (WNPSH). The displacement of WNPSH is caused by two mechanisms: i) the increase of sea surface temperature and ii) the reduction of latent heat flux over the South China Sea and adjacent western Pacific Ocean. The changes in the surface fluxes over the tropics induce a Gill-type anti-cyclonic circulation to the north of the heating anomaly and a Rossy wave train from the tropics into the midlatitude Pacific Ocean. The westerly anomalies on the northern side of the anticyclone strengthen the southwesterly flow on the western edge of WNPSH. This flow further affects the wind anomalies and moisture transport over East Asia.

Indian summer monsoon rainfall variability during 2014 and 2015 and associated Indo-Pacific upper ocean temperature patterns

Science.gov (United States)

Kakatkar, Rashmi; Gnanaseelan, C.; Chowdary, J. S.; Parekh, Anant; Deepa, J. S.

2018-02-01

In this study, factors responsible for the deficit Indian Summer Monsoon (ISM) rainfall in 2014 and 2015 and the ability of Indian Institute of Tropical Meteorology-Global Ocean Data Assimilation System (IITM-GODAS) in representing the oceanic features are examined. IITM-GODAS has been used to provide initial conditions for seasonal forecast in India during 2014 and 2015. The years 2014 and 2015 witnessed deficit ISM rainfall but were evolved from two entirely different preconditions over Pacific. This raises concern over the present understanding of the role of Pacific Ocean on ISM variability. Analysis reveals that the mechanisms associated with the rainfall deficit over the Indian Subcontinent are different in the two years. It is found that remote forcing in summer of 2015 due to El Niño is mostly responsible for the deficit monsoon rainfall through changes in Walker circulation and large-scale subsidence. In the case of the summer of 2014, both local circulation with anomalous anticyclone over central India and intrusion of mid-latitude dry winds from north have contributed for the deficit rainfall. In addition to the above, Tropical Indian Ocean (TIO) sea surface temperature (SST) and remote forcing from Pacific Ocean also modulated the ISM rainfall. It is observed that Pacific SST warming has extended westward in 2014, making it a basin scale warming unlike the strong El Niño year 2015. The eastern equatorial Indian Ocean is anomalously warmer than west in summer of 2014, and vice versa in 2015. These differences in SST in both tropical Pacific and TIO have considerable impact on ISM rainfall in 2014 and 2015. The study reveals that initializing coupled forecast models with proper upper ocean temperature over the Indo-Pacific is therefore essential for improved model forecast. It is important to note that the IITM-GODAS which assimilates only array for real-time geostrophic oceanography (ARGO) temperature and salinity profiles could capture most of the

Moisture rivals temperature in limiting photosynthesis by trees establishing beyond their cold-edge range limit under ambient and warmed conditions.

Science.gov (United States)

Moyes, Andrew B; Germino, Matthew J; Kueppers, Lara M

2015-09-01

Climate change is altering plant species distributions globally, and warming is expected to promote uphill shifts in mountain trees. However, at many cold-edge range limits, such as alpine treelines in the western United States, tree establishment may be colimited by low temperature and low moisture, making recruitment patterns with warming difficult to predict. We measured response functions linking carbon (C) assimilation and temperature- and moisture-related microclimatic factors for limber pine (Pinus flexilis) seedlings growing in a heating × watering experiment within and above the alpine treeline. We then extrapolated these response functions using observed microclimate conditions to estimate the net effects of warming and associated soil drying on C assimilation across an entire growing season. Moisture and temperature limitations were each estimated to reduce potential growing season C gain from a theoretical upper limit by 15-30% (c. 50% combined). Warming above current treeline conditions provided relatively little benefit to modeled net assimilation, whereas assimilation was sensitive to either wetter or drier conditions. Summer precipitation may be at least as important as temperature in constraining C gain by establishing subalpine trees at and above current alpine treelines as seasonally dry subalpine and alpine ecosystems continue to warm. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

Energy Technology Data Exchange (ETDEWEB)

Blok, Daan; Heijmans, Monique M P D; Berendse, Frank [Nature Conservation and Plant Ecology Group, Wageningen University, PO Box 47, 6700 AA, Wageningen (Netherlands); Schaepman-Strub, Gabriela [Institute of Evolutionary Biology and Environmental Studies, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich (Switzerland); Bartholomeus, Harm [Centre for Geo-Information, Wageningen University, PO Box 47, 6700 AA, Wageningen (Netherlands); Maximov, Trofim C, E-mail: daan.blok@wur.nl [Biological Problems of the Cryolithozone, Russian Academy of Sciences, Siberian Division, 41, Lenin Prospekt, Yakutsk, The Republic of Sakha, Yakutia 677980 (Russian Federation)

2011-07-15

Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

International Nuclear Information System (INIS)

Blok, Daan; Heijmans, Monique M P D; Berendse, Frank; Schaepman-Strub, Gabriela; Bartholomeus, Harm; Maximov, Trofim C

2011-01-01

Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

Importance of Drinking Water Temperature for Heat Stressed Pregnant Ossimi Ewes During Summer of Egypt

International Nuclear Information System (INIS)

Habeeb, A.A.M.; EL-Tarabany, A.A.; Gad, A.E.

2012-01-01

The number of 45 pregnant does with the same age and average live body weight were used in the present study. The does reared under summer hot conditions where the averages of ambient temperature and relative humidity values were 35.0 degree C and 62.5% respectively during June, July and August, 2009. Pregnant does were divided randomly into three equal groups. The 1st group drinking tap water from the source of water in the farm (30±2 degree C) and served as control. The animals in the 2nd and 3rd groups drinking cool water (20±2 degree C) and cooled water (10±2 degree C), respectively, along the experimental period which started 12 weeks before expected parturition (8 hrs daily) from 10.00 to 18.00 hrs. The results showed that drinking cool water or cold water decreased the heat load of summer season on pregnant Ossimi ewes. The respiration rate and temperatures of rectal, skin and ear values decreased significantly while daily feed intake, dry matter intake and water intake values increased significantly due to treatments when compared to those drank warm water. Blood components concentrations and estradiol, progesterone and parathormone levels in ewes drank cool or cold water were significantly higher than its levels in ewes drank warm water. The opposite was found in cortisol levels

Unexpected Impacts of Global warming on Extreme Warm Spells

Science.gov (United States)

Sardeshmukh, P. D.; Compo, G. P.; McColl, C.; Penland, C.

2017-12-01

It is generally presumed that the likelihood of extreme warm spells around the globe has increased, and will continue to increase, due to global warming. However, we find that this is generally not true in three very different types of global observational datasets and uncoupled atmospheric model simulations of the 1959 to 2012 period with prescribed observed global SSTs, sea ice, and radiative forcing changes. While extreme warm spells indeed became more common in many regions, in many other regions their likelihood remained almost the same or even decreased from the first half to the second half of this period. Such regions of unexpected changes covered nearly 40 percent of the globe in both winter and summer. The basic reason for this was a decrease of temperature variability in such regions that offset or even negated the effect of the mean temperature shift on extreme warm spell probabilities. The possibility of such an impact on extreme value probabilities was highlighted in a recent paper by Sardeshmukh, Compo, and Penland (Journal of Climate 2015). The consistency of the changes in extreme warm spell probabilities among the different observational datasets and model simulations examined suggests that they are robust regional aspects of global warming associated with atmospheric circulation changes. This highlights the need for climate models to represent not just the mean regional temperature signals but also the changes in subseasonal temperature variability associated with global warming. However, current climate models (both CMIP3 and CMIP5) generally underestimate the magnitude of the changes in the atmospheric circulation and associated temperature variability. A likely major cause of this is their continuing underestimation of the magnitude of the spatial variation of tropical SST trends. By generating an overly spatially bland tropical SST warming in response to changes in radiative forcing, the models spuriously mute tropically

Spring hydrology determines summer net carbon uptake in northern ecosystems

International Nuclear Information System (INIS)

Yi, Yonghong; Kimball, John S; Reichle, Rolf H

2014-01-01

Increased photosynthetic activity and enhanced seasonal CO 2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the normalized difference vegetation index; NDVI) and atmospheric CO 2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (⩾50° N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO 2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO 2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends. (letters)

Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

Science.gov (United States)

Yi, Yonghong; Kimball, John; Reichle, Rolf H.

2014-01-01

Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

Role of sea surface temperature anomalies in the tropical Indo-Pacific region in the northeast Asia severe drought in summer 2014: month-to-month perspective

Science.gov (United States)

Xu, Zhiqing; Fan, Ke; Wang, HuiJun

2017-09-01

The severe drought over northeast Asia in summer 2014 and the contribution to it by sea surface temperature (SST) anomalies in the tropical Indo-Pacific region were investigated from the month-to-month perspective. The severe drought was accompanied by weak lower-level summer monsoon flow and featured an obvious northward movement during summer. The mid-latitude Asian summer (MAS) pattern and East Asia/Pacific teleconnection (EAP) pattern, induced by the Indian summer monsoon (ISM) and western North Pacific summer monsoon (WNPSM) rainfall anomalies respectively, were two main bridges between the SST anomalies in the tropical Indo-Pacific region and the severe drought. Warming in the Arabian Sea induced reduced rainfall over northeast India and then triggered a negative MAS pattern favoring the severe drought in June 2014. In July 2014, warming in the tropical western North Pacific led to a strong WNPSM and increased rainfall over the Philippine Sea, triggering a positive EAP pattern. The equatorial eastern Pacific and local warming resulted in increased rainfall over the off-equatorial western Pacific and triggered an EAP-like pattern. The EAP pattern and EAP-like pattern contributed to the severe drought in July 2014. A negative Indian Ocean dipole induced an anomalous meridional circulation, and warming in the equatorial eastern Pacific induced an anomalous zonal circulation, in August 2014. The two anomalous cells led to a weak ISM and WNPSM, triggering the negative MAS and EAP patterns responsible for the severe drought. Two possible reasons for the northward movement of the drought were also proposed.

Contrasting shrub species respond to early summer temperatures leading to correspondence of shrub growth patterns

Science.gov (United States)

Weijers, Stef; Pape, Roland; Löffler, Jörg; Myers-Smith, Isla H.

2018-03-01

The Arctic-alpine biome is warming rapidly, resulting in a gradual replacement of low statured species by taller woody species in many tundra ecosystems. In northwest North America, the remotely sensed normalized difference vegetation index (NDVI), suggests an increase in productivity of the Arctic and alpine tundra and a decrease in productivity of boreal forests. However, the responses of contrasting shrub species growing at the same sites to climate drivers remain largely unexplored. Here, we test growth, climate, and NDVI relationships of two contrasting species: the expanding tall deciduous shrub Salix pulchra and the circumarctic evergreen dwarf shrub Cassiope tetragona from an alpine tundra site in the Pika valley in the Kluane Region, southwest Yukon Territories, Canada. We found that annual growth variability of both species at this site is strongly driven by early summer temperatures, despite their contrasting traits and habitats. Shrub growth chronologies for both species were correlated with the regional climate signal and showed spatial correspondence with interannual variation in NDVI in surrounding alpine and Arctic regions. Our results suggest that early summer warming represents a common driver of vegetation change for contrasting shrub species growing in different habitats in the same alpine environments.

Shifting the Arctic Carbon Balance: Effects of a Long-Term Fertilization Experiment and Anomalously Warm Temperatures on Net Ecosystem Exchange in the Alaskan Tundra

Science.gov (United States)

Ludwig, S.; Natali, S.; Rastetter, E. B.; Shaver, G. R.; Graham, L. M.; Jastrow, J. D.

2017-12-01

The arctic is warming at an accelerated rate relative to the globe. Among the predicted consequences of warming temperatures in the arctic are increased gross primary productivity (GPP), ecosystem respiration (ER), and nutrient availability. The net effect of these changes on the carbon (C) cycle and resulting C balance and feedback to climate change remain unclear. Historically the Arctic has been a C sink, but evidence from recent years suggests some regions in the Arctic are becoming C sources. To predict the role of the Arctic in global C cycling, the mechanisms affecting arctic C balances need to be better resolved. We measured net ecosystem exchange (NEE) in a long-term, multi-level, fertilization experiment at Toolik Lake, AK during an anomalously warm summer. We modeled NEE, ER, and GPP using a Bayesian network model. The best-fit model included Q10 temperature functions and linear fertilization functions for both ER and GPP. ER was more strongly affected by temperature and GPP was driven more by fertilization level. As a result, fertilization increased the C sink capacity, but only at moderate and low temperatures. At high temperatures (>28 °C) the NEE modeled for the highest level of fertilization was not significantly different from zero. In contrast, at ambient nutrient levels modeled NEE was significantly below zero (net uptake) until 35 °C, when it becomes neutral. Regardless of the level of fertilization, NEE never decreased with warming. Temperature in low ranges (5-15°C) had no net effect on NEE, whereas NEE began to increase exponentially with temperature after a threshold of 15°C until becoming a net source to the atmosphere at 37°C. Our results indicate that the C sink strength of tundra ecosystems can be increased with small increases in nutrient availability, but that large increase in nutrient availability can switch tundra ecosystems into C sources under warm conditions. Warming temperatures in tundra ecosystems will only decrease C

Temperature response of soil respiration largely unaltered with experimental warming

Science.gov (United States)

Carey, Joanna C.; Tang, Jianwu; Templer, Pamela H.; Kroeger, Kevin D.; Crowther, Thomas W.; Burton, Andrew J.; Dukes, Jeffrey S.; Emmett, Bridget; Frey, Serita D.; Heskel, Mary A.; Jiang, Lifen; Machmuller, Megan B.; Mohan, Jacqueline; Panetta, Anne Marie; Reich, Peter B.; Reinsch, Sabine; Wang, Xin; Allison, Steven D.; Bamminger, Chris; Bridgham, Scott; Collins, Scott L.; de Dato, Giovanbattista; Eddy, William C.; Enquist, Brian J.; Estiarte, Marc; Harte, John; Henderson, Amanda; Johnson, Bart R.; Steenberg Larsen, Klaus; Luo, Yiqi; Marhan, Sven; Melillo, Jerry M.; Penuelas, Josep; Pfeifer-Meister, Laurel; Poll, Christian; Rastetter, Edward B.; Reinmann, Andrew B.; Reynolds, Lorien L.; Schmidt, Inger K.; Shaver, Gaius R.; Strong, Aaron L.; Suseela, Vidya; Tietema, Albert

2016-01-01

The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic warming.

Formation of well-mixed warm water column in central Bohai Sea during summer: Role of high-frequency atmospheric forcing

Science.gov (United States)

Ma, Weiwei; Wan, Xiuquan; Wang, Zhankun; Liu, Yulong; Wan, Kai

2017-12-01

The influence of high-frequency atmospheric forcing on the formation of a well-mixed summer warm water column in the central Bohai Sea is investigated comparing model simulations driven by daily surface forcing and those using monthly forcing data. In the absence of high-frequency atmospheric forcing, numerical simulations have repeatedly failed to reproduce this vertically uniform column of warm water measured over the past 35 years. However, high-frequency surface forcing is found to strongly influence the structure and distribution of the well-mixed warm water column, and simulations are in good agreement with observations. Results show that high frequency forcing enhances vertical mixing over the central bank, intensifies downward heat transport, and homogenizes the water column to form the Bohai central warm column. Evidence presented shows that high frequency forcing plays a dominant role in the formation of the well-mixed warm water column in summer, even without the effects of tidal and surface wave mixing. The present study thus provides a practical and rational way of further improving the performance of oceanic simulations in the Bohai Sea and can be used to adjust parameterization schemes of ocean models.

A Centennial Episode of Weak East Asian Summer Monsoon in the Midst of the Medieval Warming

Science.gov (United States)

Jin, C.; Liu, J.; Wang, B.; Wang, Z.; Yan, M.

2017-12-01

Recent paleo-proxy evidences suggested that the East Asian summer monsoon (EASM) was generally strong (i.e., northern China wet and southern China dry) during the Medieval Warm Period (MWP, 9th to the mid-13th century), however, there was a centennial period (around 11th century) during which the EASM was weak. This study aims to explore the causes of this centennial weak EASM episode and in general, what controls the centennial variability of the EASM in the pre-industrial period of AD 501-1850. With the Community Earth System Model (CESM), a suit of control and forced experiments were conducted for the past 2000 years. The model run with all external forcings simulates a warm period of EA from AD 801-1250 with a generally increased summer mean precipitation over the northern EA; however, during the 11th century (roughly from AD 980 to AD 1100), the EASM is significantly weaker than the other periods during the MWP. We find that on the multi-decadal to centennial time scale, a strong EASM is associated with a La Nina-like Indo-Pacific warming and the opposite is also true. This sea surface temperature (SST) anomaly pattern represents the leading EOF mode of centennial SST variations, and it is primarily forced by the solar radiation and volcanic activity, whereas the land use/land cover and greenhouse gases as well as internal dynamics play a negligible role. During the MWP, the solar forcing plays a dominate role in supporting the SST variation as the volcanic activity is weak. The weakening of the EASM during the AD 980-1100 is attributed to the relatively low solar radiation, which leads to a prevailing El Nino-like Indo-Pacific cooling with strongest cooling occurring in the equatorial western Pacific. The suppressed convection over the equatorial western Pacific directly induces a Philippine Sea anticyclone anomaly, which increases southern China precipitation, meanwhile suppresses Philippine Sea precipitation, exciting a meridional teleconnection that

Effects of Ambient Temperature and Forced-air Warming on Intraoperative Core Temperature: A Factorial Randomized Trial.

Science.gov (United States)

Pei, Lijian; Huang, Yuguang; Xu, Yiyao; Zheng, Yongchang; Sang, Xinting; Zhou, Xiaoyun; Li, Shanqing; Mao, Guangmei; Mascha, Edward J; Sessler, Daniel I

2018-05-01

The effect of ambient temperature, with and without active warming, on intraoperative core temperature remains poorly characterized. The authors determined the effect of ambient temperature on core temperature changes with and without forced-air warming. In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was core temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient temperature, warming method, and their interaction. A 1°C increase in ambient temperature attenuated the negative slope of core temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °Ccore/(h°Cambient) (P ambient temperature with passive insulation, but was unaffected by ambient temperature during forced-air warming (0.02 [98.3% CI, -0.04 to 0.09] °Ccore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, core temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients. Ambient intraoperative temperature has a negligible effect on core temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient temperature can thus be set to comfortable levels for staff in patients who are actively warmed.

An observational study on the temperature rising effects in water warming canal and water warming pond

Energy Technology Data Exchange (ETDEWEB)

Hong, J. B.; Hong, S. B. [Rural Development Cooperation, Seoul (Korea, Republic of)

1990-09-15

The power water flowed out from the multipurpose darn influences the ecosystem approximately because of the low water temperature. An appropriate counter measure to the rising water temperature is needed for growing crops especially when the temperature is below 18°C in the source of the irrigation water This observational study is practiced in Yong-Doo water warming canal and pond in the down stream of Choong-Ju multipurpose dam and is practiced for analyse and compare the rising effects in actural water temperature by actual measurement with the rising effects of planned water temperatuer by the basic theoritical method and for the help to present the direction in plan establishment through investigate the results afterwards. The results are as follows. 1. The degree of the rise of the water temperature can be decided by θ{sub x} = θ{sub 0} + K (L/(v * h)) * (T - θ{sub 0}) Then, K values of a factor representing the characteristics of the water warming canal were 0.00002043 for the type I. and 0.0000173 for the type II. respectively. 2. A variation of water temperature which produced by the difference effective temperature and water temperature in the water warming canal was θ{sub x1} = 16.5 + 15.9 (1-e{sup -0.00018x}), θ{sub x2} = 18.8 + 8.4(1-e{sup -0.000298x}) for the type I. and θ{sub x} = 19.6 + 12.8 (1-e{sup -0.00041x}) for the type II. 3. It was shown that the effects of the rise of water temperature for the type I. water warming canal were greater than that of type II. as a resultes of broadening the surface of the canal compared with the depth of water, coloring the surface of water canal and installing the resistance block. 4. In case of the type I. water warming canal, the equation between the air temperature and the degree of the rise of water temprature could be made; Y = 0.4134X + 7.728 In addition, in case of the type II. water warming canal, the correlation was very low. 5. A monthly variation of the water temperature in the water warming

Comparison of instrumental and interpolated meteorological data-based summer temperature reconstructions on Mt. Taibai in the Qinling Mountains, northwestern China

Science.gov (United States)

Qin, Jin; Bai, Hongying; Su, Kai; Liu, Rongjuan; Zhai, Danping; Wang, Jun; Li, Shuheng; Zhou, Qi; Li, Bin

2018-01-01

Previous dendroclimatical studies have been based on the relationship between tree growth and instrumental climate data recorded at lower land meteorological stations, but the climate conditions somehow differ between sampling sites and distant population centers. Thus, in this study, we performed a comparison between the 152-year reconstruction of June to July mean air temperature on the basis of interpolated meteorological data and instrumental meteorological data. The reconstruction explained 38.7% of the variance in the interpolated temperature data (37.2% after the degrees of freedom were adjusted) and 39.6% of the variance in the instrumental temperature data (38.4% after adjustment for loss of degrees of freedom) during the period 1962-2013 AD. The first global warming (the 1920s) and recent warming (1990-2013) found from the reconstructed temperature series match reasonably well with two other reported summer temperature reconstructions from north-central China. Cold periods occurred three times during 1866-1885, 1901-1921, and 1981-2000, while hot periods occurred four times during 1886-1900, 1922-1933, 1953-1966, and 2001-2007. The extreme warm (cold) years are coherent with the documentary drought (flood) events. Significant 31-22-year, 22-18-year, and 12-8-year cycles indicate major fluctuations in regional temperatures may reflect large-scale climatic shifts.

Impacts of half a degree additional warming on the Asian summer monsoon rainfall characteristics

Science.gov (United States)

Lee, Donghyun; Min, Seung-Ki; Fischer, Erich; Shiogama, Hideo; Bethke, Ingo; Lierhammer, Ludwig; Scinocca, John F.

2018-04-01

This study investigates the impacts of global warming of 1.5 °C and 2.0 °C above pre-industrial conditions (Paris Agreement target temperatures) on the South Asian and East Asian monsoon rainfall using five atmospheric global climate models participating in the ‘Half a degree Additional warming, Prognosis and Projected Impacts’ (HAPPI) project. Mean and extreme precipitation is projected to increase under warming over the two monsoon regions, more strongly in the 2.0 °C warmer world. Moisture budget analysis shows that increases in evaporation and atmospheric moisture lead to the additional increases in mean precipitation with good inter-model agreement. Analysis of daily precipitation characteristics reveals that more-extreme precipitation will have larger increase in intensity and frequency responding to the half a degree additional warming, which is more clearly seen over the South Asian monsoon region, indicating non-linear scaling of precipitation extremes with temperature. Strong inter-model relationship between temperature and precipitation intensity further demonstrates that the increased moisture with warming (Clausius-Clapeyron relation) plays a critical role in the stronger intensification of more-extreme rainfall with warming. Results from CMIP5 coupled global climate models under a transient warming scenario confirm that half a degree additional warming would bring more frequent and stronger heavy precipitation events, exerting devastating impacts on the human and natural system over the Asian monsoon region.

Seasonal modulation of the Asian summer monsoon between the Medieval Warm Period and Little Ice Age: a multi model study

Science.gov (United States)

Kamae, Youichi; Kawana, Toshi; Oshiro, Megumi; Ueda, Hiroaki

2017-12-01

Instrumental and proxy records indicate remarkable global climate variability over the last millennium, influenced by solar irradiance, Earth's orbital parameters, volcanic eruptions and human activities. Numerical model simulations and proxy data suggest an enhanced Asian summer monsoon during the Medieval Warm Period (MWP) compared to the Little Ice Age (LIA). Using multiple climate model simulations, we show that anomalous seasonal insolation over the Northern Hemisphere due to a long cycle of orbital parameters results in a modulation of the Asian summer monsoon transition between the MWP and LIA. Ten climate model simulations prescribing historical radiative forcing that includes orbital parameters consistently reproduce an enhanced MWP Asian monsoon in late summer and a weakened monsoon in early summer. Weakened, then enhanced Northern Hemisphere insolation before and after June leads to a seasonally asymmetric temperature response over the Eurasian continent, resulting in a seasonal reversal of the signs of MWP-LIA anomalies in land-sea thermal contrast, atmospheric circulation, and rainfall from early to late summer. This seasonal asymmetry in monsoon response is consistently found among the different climate models and is reproduced by an idealized model simulation forced solely by orbital parameters. The results of this study indicate that slow variation in the Earth's orbital parameters contributes to centennial variability in the Asian monsoon transition.[Figure not available: see fulltext.

Temperature adaptation of bacterial communities in experimentally warmed forest soils.

Science.gov (United States)

Rousk, Johannes; Frey, Serita D; Bååth, Erland

2012-10-01

A detailed understanding of the influence of temperature on soil microbial activity is critical to predict future atmospheric CO 2 concentrations and feedbacks to anthropogenic warming. We investigated soils exposed to 3-4 years of continuous 5 °C-warming in a field experiment in a temperate forest. We found that an index for the temperature adaptation of the microbial community, T min for bacterial growth, increased by 0.19 °C per 1 °C rise in temperature, showing a community shift towards one adapted to higher temperature with a higher temperature sensitivity (Q 10(5-15 °C) increased by 0.08 units per 1 °C). Using continuously measured temperature data from the field experiment we modelled in situ bacterial growth. Assuming that warming did not affect resource availability, bacterial growth was modelled to become 60% higher in warmed compared to the control plots, with the effect of temperature adaptation of the community only having a small effect on overall bacterial growth (bacterial growth, most likely due to substrate depletion because of the initially higher growth in warmed plots. When this was factored in, the result was similar rates of modelled in situ bacterial growth in warmed and control plots after 3 years, despite the temperature difference. We conclude that although temperature adaptation for bacterial growth to higher temperatures was detectable, its influence on annual bacterial growth was minor, and overshadowed by the direct temperature effect on growth rates. © 2012 Blackwell Publishing Ltd.

Evaluation of surface air temperature trend and climate change in the north - east of I. R. of Iran

International Nuclear Information System (INIS)

Alireza, Shahabfar

2004-01-01

In this paper maximum, minimum and mean surface air temperature recorded, analysed to reveal spatial and temporal patterns of long-term trends, change points, significant warming (cooling) periods and linear trend per decade. According to this research summer minimum temperatures have generally increased at a larger rate than in spring and autumn minimum temperatures. On the other hand, nighttime warming rates of spring and summer are generally stronger than those that exist in spring and summer daytime temperatures. Considering the significant increasing trends in annual, spring and summer temperatures, it is seen that night-time warming rates are stronger in the northern regions, which are characterized by the Khorasan Province macro climate type: a very hot summer, a relatively hot and late spring and early autumn, and a moderate winter. We have seriously considered the strong warming trends in spring and summer and thus likely in annual minimum air temperatures. It is very likely that significant and very rapid night-time warming trends over much of the province can be related to the widespread, rapid and increased urbanization in Khorasan Province, in addition to long-term and global effects of the human-induced climate change on air temperatures. (Author)

Warming and Acidification Induced Mass Mortality of a Coastal Keystone predator

Science.gov (United States)

Melzner, F.; Findeisen, U.

2016-02-01

The Baltic Sea is characterized by low salinity and pronounced fluctuations in pCO2. On-line monitoring of pCO2 in 2014 in Kiel Fjord demonstrated occurrence of peak values of >2,000 µatm in summer and autumn and average values >750 µatm. We assessed the impacts of elevated temperature (ambient temperature, ambient +3°C) and pCO2 (500, 1,500, 2,400 µatm) on the keystone species Asterias rubens in a fully crossed long - term experiment (N=5 replicate tanks each, 1 year duration). During spring and early summer (February - June), high temperature animals ingested significantly more food and spawned significantly earlier (April 30th) than ambient acclimated animals (May 23rd). Elevated pCO2 led to comparatively minor reductions in food intake and scope for growth during that period. During summer (June - August), elevated temperature >25°C caused negative energy budgets and >95% mortality in the warm acclimated groups, while mortality was low in the ambient temperature groups. Our results indicate that A. rubens may benefit from increased temperature during colder months, yet dramatically suffer during summer heat waves in warm years. Meaningful experimental approaches to assess species vulnerability to climate change need to encompass all seasons and realistic abiotic stressor levels.

Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore.

Science.gov (United States)

Albon, Steve D; Irvine, R Justin; Halvorsen, Odd; Langvatn, Rolf; Loe, Leif E; Ropstad, Erik; Veiberg, Vebjørn; van der Wal, René; Bjørkvoll, Eirin M; Duff, Elizabeth I; Hansen, Brage B; Lee, Aline M; Tveraa, Torkild; Stien, Audun

2017-04-01

The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity. As body condition is a 'barometer' of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994 to 2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between-year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long-term trend (coefficient of variation, CV = 8.8%) and was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to 'rain-on-snow' events. October body mass (CV = 2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density-dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important 'missing' mechanistic link in the current understanding of the population biology of a

Are winter-active species vulnerable to climate warming? A case study with the wintergreen terrestrial orchid, Tipularia discolor.

Science.gov (United States)

Marchin, Renée M; Dunn, Robert R; Hoffmann, William A

2014-12-01

In the eastern United States, winter temperature has been increasing nearly twice as fast as summer temperature, but studies of warming effects on plants have focused on species that are photosynthetically active in summer. The terrestrial orchid Tipularia discolor is leafless in summer and acquires C primarily in winter. The optimum temperature for photosynthesis in T. discolor is higher than the maximum temperature throughout most of its growing season, and therefore growth can be expected to increase with warming. Contrary to this hypothesis, experimental warming negatively affected reproductive fitness (number of flowering stalks, flowers, fruits) and growth (change in leaf area from 2010 to 2012) in T. discolor. Temperature in June-July was critical for flowering, and mean July temperature greater than 29 °C (i.e., 2.5 °C above ambient) eliminated reproduction. Warming of 1.2 °C delayed flowering by an average of 10 days and fruiting by an average of 5 days. Warming of 4.4 °C reduced relative growth rates by about 60%, which may have been partially caused by the direct effects of temperature on photosynthesis and respiration. Warming indirectly increased vapor pressure deficit (VPD) by 0.2-0.5 kPa, and leaf-to-air VPD over 1.3 kPa restricted stomatal conductance of T. discolor to 10-40% of maximum conductance. These results highlight the need to account for changes in VPD when estimating temperature responses of plant species under future warming scenarios. Increasing temperature in the future will likely be an important limiting factor to the distribution of T. discolor, especially along the southern edge of its range.

Effects of Major Sudden Stratospheric Warmings Identified in Midlatitude Mesospheric Rayleigh-Scatter Lidar Temperatures

Science.gov (United States)

Sox, L.; Wickwar, V. B.; Fish, C. S.; Herron, J. P.

2014-12-01

Mesospheric temperature anomalies associated with Sudden Stratospheric Warmings (SSWs) have been observed extensively in the polar regions. However, observations of these anomalies at midlatitudes are sparse. The very dense 11-year data set, collected between 1993-2004, with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory (ALO; 41.7°N, 111.8°W) at the Center for Atmospheric and Space Sciences (CASS) on the campus of Utah State University (USU), has been carefully examined for such anomalies. The temperatures derived from these data extend over the mesosphere, from 45 to 90 km. During this period extensive data were acquired during seven major SSW events. In this work we aim to determine the characteristics of the midlatitude mesospheric temperatures during these seven major SSWs. To do this, comparisons were made between the temperature profiles on individual nights before, during, and after the SSW events and the corresponding derived climatological temperature profiles (31-day by 11-year average) for those nights. A consistent disturbance pattern was observed in the mesospheric temperatures during these SSWs. A distinct shift from the nominal winter temperature pattern to a pattern more characteristic of summer temperatures was seen in the midlatitude mesosphere close to when the zonal winds in the polar stratosphere (at 10 hPa, 60° N) reversed from eastward to westward. This shift lasted for several days. This change in pattern included coolings in the upper mesosphere, comparable to those seen in the polar regions, and warmings in the lower mesosphere.

Differential responses of invasive and native plants to warming with simulated changes in diurnal temperature ranges.

Science.gov (United States)

Chen, Bao-Ming; Gao, Yang; Liao, Hui-Xuan; Peng, Shao-Lin

2017-07-01

Although many studies have documented the effects of global warming on invasive plants, little is known about whether the effects of warming on plant invasion differ depending on the imposed change in different diurnal temperature ranges (DTR). We tested the impact of warming with DTR change on seed germination and seedling growth of eight species in the family Asteraceae. Four of these are invasive ( Eupatorium catarium , Mikania micrantha , Biodens pilosa var. radiate , Ageratum conyzoides ) in China, and four are native ( Sonchus arvensis , Senecios candens , Pterocypsela indica , Eupatorium fortunei ). Four temperature treatments were set in growth chambers (three warming by 3 °C with different DTRs and control), and experiments were run to mimic wintertime and summertime conditions. The control treatment ( T c ) was set to the mean temperature for the corresponding time of year, and the three warming treatments were symmetric (i.e. equal night-and-day) (DTR sym ), asymmetric warming with increased (DTR inc ) and decreased (DTR dec ) DTR. The warming treatments did not affect seed germination of invasive species under any of the conditions, but DTR sym and DTR inc increased seed germination of natives relative to the control, suggesting that warming may not increase success of these invasive plant species via effects on seed germination of invasive plants relative to native plants. The invasive plants had higher biomass and greater stem allocation than the native ones under all of the warming treatments. Wintertime warming increased the biomass of the invasive and wintertime DTR sym and DTR inc increased that of the native plants, whereas summertime asymmetric warming decreased the biomass of the invasives but not the natives. Therefore, warming may not facilitate invasion of these invasive species due to the suppressive effects of summertime warming (particularly the asymmetric warming) on growth. Compared with DTR sym , DTR dec decreased the biomass of

A 560 yr summer temperature reconstruction for the Western Mediterranean basin based on stable carbon isotopes from Pinus nigra ssp. laricio (Corsica/France

Directory of Open Access Journals (Sweden)

J. Kuhlemann

2012-10-01

Full Text Available The Mediterranean is considered as an area which will be affected strongly by current climate change. However, temperature records for the past centuries which can contribute to a better understanding of future climate changes are still sparse for this region. Carbon isotope chronologies from tree-rings often mirror temperature history but their application as climate proxies is difficult due to the influence of the anthropogenic change in atmospheric CO2 on the carbon isotope fractionation during photosynthetic CO2 uptake. We tested the influence of different correction models accounting for plant response to increased atmospheric CO2 on four annually resolved long-term carbon isotope records (between 400 and 800 yr derived from Corsican pine trees (Pinus nigra ssp. laricio growing at ecologically varying mountain sites on the island of Corsica. The different correction factors have only a minor influence on the main climate signals and resulting temperature reconstructions. Carbon isotope series show strong correlations with summer temperature and precipitation. A summer temperature reconstruction (1448–2007 AD reveals that the Little Ice Age was characterised by low, but not extremely low temperatures on Corsica. Temperatures have been to modern temperatures at around 1500 AD. The reconstruction reveals warm summers during 1480–1520 and 1950–2007 AD and cool summers during 1580–1620 and 1820–1890 AD.

Leaf anatomical and photosynthetic acclimation to cool temperature and high light in two winter versus two summer annuals.

Science.gov (United States)

Cohu, Christopher M; Muller, Onno; Adams, William W; Demmig-Adams, Barbara

2014-09-01

Acclimation of foliar features to cool temperature and high light was characterized in winter (Spinacia oleracea L. cv. Giant Nobel; Arabidopsis thaliana (L.) Heynhold Col-0 and ecotypes from Sweden and Italy) versus summer (Helianthus annuus L. cv. Soraya; Cucurbita pepo L. cv. Italian Zucchini Romanesco) annuals. Significant relationships existed among leaf dry mass per area, photosynthesis, leaf thickness and palisade mesophyll thickness. While the acclimatory response of the summer annuals to cool temperature and/or high light levels was limited, the winter annuals increased the number of palisade cell layers, ranging from two layers under moderate light and warm temperature to between four and five layers under cool temperature and high light. A significant relationship was also found between palisade tissue thickness and either cross-sectional area or number of phloem cells (each normalized by vein density) in minor veins among all four species and growth regimes. The two winter annuals, but not the summer annuals, thus exhibited acclimatory adjustments of minor vein phloem to cool temperature and/or high light, with more numerous and larger phloem cells and a higher maximal photosynthesis rate. The upregulation of photosynthesis in winter annuals in response to low growth temperature may thus depend on not only (1) a greater volume of photosynthesizing palisade tissue but also (2) leaf veins containing additional phloem cells and presumably capable of exporting a greater volume of sugars from the leaves to the rest of the plant. © 2014 Scandinavian Plant Physiology Society.

Early-Holocene decoupled summer temperature and monsoon precipitation in southwest China

Science.gov (United States)

Wu, D.; Chen, F.; Chen, X.; Lv, F.; Zhou, A.; Chen, J.; Abbott, M. B.; Yu, J.

2017-12-01

Proxy based reconstructions of Holocene temperature have shown that both the timing and magnitude of the thermal maximum vary substantially between different regions; the simulations results from climate models also show that summers were substantially cooler over regions directly influenced by the presence of the Laurentide ice sheet during the early Holocene, whereas other regions of the Northern Hemisphere were dominated by orbital forcing. However, for lack of summer temperature reconstruction in the low latitude regions like southwestern China dominated by the Indian summer monsoon, the Holocene summer temperature variations and it underlying forcing mechanism are ambiguous. Here we present a well-dated record of pollen-based quantitative summer temperature (mean July; MJT) over the last 14000 years from Xingyun Lake, Yunnan Province, southwest China. It was found that MJT decreased during the YD event, then increased slowly until 7400 yr BP, and decreased thereafter. The MJT shows a pattern with middle Holocene maximum of MJT, indicating a different changing pattern with the carbonate oxygen isotope record (d18O) from the same core during the early Holocene (11500-7400 yr BP), which has the similar variation with speleothem d18O record from Dongge cave, both indicate the variation of monsoon precipitation with the highest precipitation occurred during the early Holocene. Therefore, we propose that the variation of summer temperature and precipitation in southwest China was decoupled during the early Holocene. However, both MJT and monsoon precipitation decreased after the middle Holocene following the boreal summer insolation. We suggest that the high precipitation with strong summer monsoon and hence higher cloud cover may depress the temperature increasing forced by increasing summer insolation during the early Holocene; while melting ice-sheet in the high latitude regions had strongly influenced the summer temperature increase during the deglacial period

Temperature response of soil respiration largely unaltered with experimental warming

DEFF Research Database (Denmark)

Carey, Joanna C; Tang, Jianwu; Templer, Pamela H

2016-01-01

The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific...... attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies......, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation...

Impact of ocean acidification and warming on the Mediterranean mussel (Mytilus galloprovincialis

Directory of Open Access Journals (Sweden)

Frédéric eGazeau

2014-11-01

Full Text Available In order to assess the effects of ocean acidification and warming on the Mediterranean mussel (Mytilus galloprovincialis, specimens were reared in aquarium tanks and exposed to elevated conditions of temperature (+3 °C and acidity (-0.3 pH units for a period of 10 months. The whole system comprised a factorial experimental design with 4 treatments (3 aquaria per treatment: control, lowered pH, elevated temperature and lowered pH/elevated temperature. Mortality was estimated on a weekly basis and every 2 months, various biometrical parameters and physiological processes were measured: somatic and shell growth, metabolic rates and body fluid acid-base parameters. Mussels were highly sensitive to warming, with 100 % mortality observed under elevated temperature at the end of our experiment in October. Mortality rates increased drastically in summer, when water temperature exceeded 25 °C. In contrast, our results suggest that survival of this species will not be affected by a pH decrease of ~0.3 in the Mediterranean Sea. Somatic and shell growth did not appear very sensitive to ocean acidification and warming during most of the experiment, but were reduced, after summer, in the lowered pH treatment. This was consistent with measured shell net dissolution and observed loss of periostracum, as well as uncompensated extracellular acidosis in the lowered pH treatment indicating a progressive insufficiency in acid-base regulation capacity. However, based on the present dataset, we cannot elucidate if these decreases in growth and regulation capacities after summer are a consequence of lower pH levels during that period or a consequence of a combined effect of acidification and warming. To summarize, while ocean acidification will potentially contribute to lower growth rates, especially in summer when mussels are exposed to sub-optimal conditions, ocean warming will likely pose more serious threats to Mediterranean mussels in this region in the coming

Influence of the sea surface temperature anomaly over the Indian Ocean in March on the summer rainfall in Xinjiang

Science.gov (United States)

Zhou, Yang; Huang, Anning; Zhao, Yong; Yang, Qing; Jiang, Jing; La, Mengke

2015-02-01

This study explores the relationship between the sea surface temperature over the Indian Ocean (IOSST) in March and the summer rainfall in Xinjiang. In the observations, the IOSST in March significantly correlates with the summer rainfall in Xinjiang with a correlation coefficient of about 0.49 during 1961-2007. This relationship is independent from the El Niño Southern Oscillation (ENSO), with a partial correlation coefficient of about 0.40-0.48 controlling for the ENSO indices from December to March. In addition to the observations, three sets of numerical sensitivity experiments are conducted with a regional climate model (RegCM4.3). The model results show that warm IOSST can excite a negative anomaly of geopotential height at 500 hPa over the Indian Ocean in March. This anomaly stays over the tropical Indian Ocean, and then propagates north to central Asia in June. Consequently, the anomalous wind associated with this geopotential height anomaly transports moisture from the Persian Gulf and the coast of Iran to Xinjiang, passing over Pakistan and the Tibetan Plateau. Therefore, the warm (cold) IOSST in March tends to cause the increase (decrease) of the summer rainfall over Xinjiang, especially in the Tian Shan and Kunlun Mountains.

The European climate under a 2 °C global warming

International Nuclear Information System (INIS)

Vautard, Robert; Stegehuis, Annemiek; Gobiet, Andreas; Mendlik, Thomas; Sobolowski, Stefan; Kjellström, Erik; Nikulin, Grigory; Watkiss, Paul; Landgren, Oskar; Teichmann, Claas; Jacob, Daniela

2014-01-01

A global warming of 2 °C relative to pre-industrial climate has been considered as a threshold which society should endeavor to remain below, in order to limit the dangerous effects of anthropogenic climate change. The possible changes in regional climate under this target level of global warming have so far not been investigated in detail. Using an ensemble of 15 regional climate simulations downscaling six transient global climate simulations, we identify the respective time periods corresponding to 2 °C global warming, describe the range of projected changes for the European climate for this level of global warming, and investigate the uncertainty across the multi-model ensemble. Robust changes in mean and extreme temperature, precipitation, winds and surface energy budgets are found based on the ensemble of simulations. The results indicate that most of Europe will experience higher warming than the global average. They also reveal strong distributional patterns across Europe, which will be important in subsequent impact assessments and adaptation responses in different countries and regions. For instance, a North–South (West–East) warming gradient is found for summer (winter) along with a general increase in heavy precipitation and summer extreme temperatures. Tying the ensemble analysis to time periods with a prescribed global temperature change rather than fixed time periods allows for the identification of more robust regional patterns of temperature changes due to removal of some of the uncertainty related to the global models’ climate sensitivity. (paper)

Chronic environmental stress enhances tolerance to seasonal gradual warming in marine mussels.

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Ionan Marigómez

Full Text Available In global climate change scenarios, seawater warming acts in concert with multiple stress sources, which may enhance the susceptibility of marine biota to thermal stress. Here, the responsiveness to seasonal gradual warming was investigated in temperate mussels from a chronically stressed population in comparison with a healthy one. Stressed and healthy mussels were subjected to gradual temperature elevation for 8 days (1°C per day; fall: 16-24°C, winter: 12-20°C, summer: 20-28°C and kept at elevated temperature for 3 weeks. Healthy mussels experienced thermal stress and entered the time-limited survival period in the fall, became acclimated in winter and exhibited sublethal damage in summer. In stressed mussels, thermal stress and subsequent health deterioration were elicited in the fall but no transition into the critical period of time-limited survival was observed. Stressed mussels did not become acclimated to 20°C in winter, when they experienced low-to-moderate thermal stress, and did not experience sublethal damage at 28°C in summer, showing instead signs of metabolic rate depression. Overall, although the thermal threshold was lowered in chronically stressed mussels, they exhibited enhanced tolerance to seasonal gradual warming, especially in summer. These results challenge current assumptions on the susceptibility of marine biota to the interactive effects of seawater warming and pollution.

Joint influence of the Indo-Pacific Warm Pool and Northern Arabian Sea Temperatures on the Indian Summer Monsoon in a Global Climate Model Simulation

Science.gov (United States)

Befort, Daniel J.; Leckebusch, Gregor C.; Cubasch, Ulrich

2016-04-01

Proxy-based studies confirmed that the Indian Summer Monsoon (ISM) shows large variations during the Holocene. These changes might be explained by changes in orbital conditions and solar insolation but are also thought to be associated to changes in oceanic conditions, e.g. over the Indo-Pacific-Warm-Pool region. However, due to the nature of these (proxy-based) analyses no conclusion about atmospheric circulation changes during dry and wet epochs are possible. Here, a fully-coupled global climate simulation (AOGCM) covering the past 6000 years is analysed regarding ISM variability. Several dry and wet epochs are found, the most striking around 2ka BP (dry) and 1.7ka BP (wet). As only orbital parameters change during integration, we expect these "shorter-term" changes to be associated with changes in oceanic conditions. During 1.7ka BP the sea surface temperatures (SST) over the Northern Arabian Sea (NARAB) are significantly warmer compared to 2ka BP, whereas cooler conditions are found over the western Pacific Ocean. Additionally, significant differences are found over large parts of the North Atlantic. To explain in how far these different ocean basins are responsible for anomalous conditions during 1.7ka BP, several sensitivity experiments with changed SST/SIC conditions are carried out. It is found that neither the SST's in the Pacific nor in the Indian Ocean are able to reproduce the anomalous rainfall and atmospheric circulation patterns during 1.7ka on its own. Instead, anomalous dry conditions during 2ka BP and wet conditions during 1.7ka BP are associated with a shift of the Indo-Pacific-Warm-Pool (IPWP) and simultaneous anomalous sea-surface temperatures over the NARAB region. Eventually, it is tested in how far this hypothesis holds true for other dry and wet events in the AOGCM data during the whole 6000 years. In general, a shift of the IPWP without anomalous SST conditions over the NARAB region (and vice versa) is not sufficient to cause long

A zero-power warming chamber for investigating plant responses to rising temperature

Directory of Open Access Journals (Sweden)

K. F. Lewin

2017-09-01

Full Text Available Advances in understanding and model representation of plant and ecosystem responses to rising temperature have typically required temperature manipulation of research plots, particularly when considering warming scenarios that exceed current climate envelopes. In remote or logistically challenging locations, passive warming using solar radiation is often the only viable approach for temperature manipulation. However, current passive warming approaches are only able to elevate the mean daily air temperature by  ∼  1.5 °C. Motivated by our need to understand temperature acclimation in the Arctic, where warming has been markedly greater than the global average and where future warming is projected to be  ∼  2–3 °C by the middle of the century; we have developed an alternative approach to passive warming. Our zero-power warming (ZPW chamber requires no electrical power for fully autonomous operation. It uses a novel system of internal and external heat exchangers that allow differential actuation of pistons in coupled cylinders to control chamber venting. This enables the ZPW chamber venting to respond to the difference between the external and internal air temperatures, thereby increasing the potential for warming and eliminating the risk of overheating. During the thaw season on the coastal tundra of northern Alaska our ZPW chamber was able to elevate the mean daily air temperature 2.6 °C above ambient, double the warming achieved by an adjacent passively warmed control chamber that lacked our hydraulic system. We describe the construction, evaluation and performance of our ZPW chamber and discuss the impact of potential artefacts associated with the design and its operation on the Arctic tundra. The approach we describe is highly flexible and tunable, enabling customization for use in many different environments where significantly greater temperature manipulation than that possible with existing passive warming

A zero-power warming chamber for investigating plant responses to rising temperature

Science.gov (United States)

Lewin, Keith F.; McMahon, Andrew M.; Ely, Kim S.; Serbin, Shawn P.; Rogers, Alistair

2017-09-01

Advances in understanding and model representation of plant and ecosystem responses to rising temperature have typically required temperature manipulation of research plots, particularly when considering warming scenarios that exceed current climate envelopes. In remote or logistically challenging locations, passive warming using solar radiation is often the only viable approach for temperature manipulation. However, current passive warming approaches are only able to elevate the mean daily air temperature by ˜ 1.5 °C. Motivated by our need to understand temperature acclimation in the Arctic, where warming has been markedly greater than the global average and where future warming is projected to be ˜ 2-3 °C by the middle of the century; we have developed an alternative approach to passive warming. Our zero-power warming (ZPW) chamber requires no electrical power for fully autonomous operation. It uses a novel system of internal and external heat exchangers that allow differential actuation of pistons in coupled cylinders to control chamber venting. This enables the ZPW chamber venting to respond to the difference between the external and internal air temperatures, thereby increasing the potential for warming and eliminating the risk of overheating. During the thaw season on the coastal tundra of northern Alaska our ZPW chamber was able to elevate the mean daily air temperature 2.6 °C above ambient, double the warming achieved by an adjacent passively warmed control chamber that lacked our hydraulic system. We describe the construction, evaluation and performance of our ZPW chamber and discuss the impact of potential artefacts associated with the design and its operation on the Arctic tundra. The approach we describe is highly flexible and tunable, enabling customization for use in many different environments where significantly greater temperature manipulation than that possible with existing passive warming approaches is desired.

Global assessment of experimental climate warming on tundra vegetation

DEFF Research Database (Denmark)

Elmendorf, Sarah C.; Henry, Gregory H.R.; Hollister, Robert D.

2012-01-01

Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations...... of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups...... to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed...

Excess mortality during the warm summer of 2015 in Switzerland.

Science.gov (United States)

Vicedo-Cabrera, Ana M; Ragettli, Martina S; Schindler, Christian; Röösli, Martin

2016-01-01

In Switzerland, summer 2015 was the second warmest summer for 150 years (after summer 2003). For summer 2003, a 6.9% excess mortality was estimated for Switzerland, which corresponded to 975 extra deaths. The impact of the heat in summer 2015 in Switzerland has not so far been evaluated. Daily age group-, gender- and region-specific all-cause excess mortality during summer (June-August) 2015 was estimated, based on predictions derived from quasi-Poisson regression models fitted to the daily mortality data for the 10 previous years. Estimates of excess mortality were derived for 1 June to 31 August, at national and regional level, as well as by month and for specific heat episodes identified in summer 2015 by use of seven different definitions. 804 excess deaths (5.4%, 95% confidence interval [CI] 3.0‒7.9%) were estimated for summer 2015 compared with previous summers, with the highest percentage obtained for July (11.6%, 95% CI 3.7‒19.4%). Seventy-seven percent of deaths occurred in people aged 75 years and older. Ticino (10.3%, 95% CI -1.8‒22.4%), Northwestern Switzerland (9.5%, 95% CI 2.7‒16.3%) and Espace Mittelland (8.9%, 95% CI 3.7‒14.1%) showed highest excess mortality during this three-month period, whereas fewer deaths than expected (-3.3%, 95% CI -9.2‒2.6%) were observed in Eastern Switzerland, the coldest region. The largest excess estimate of 23.7% was obtained during days when both maximum apparent and minimum night-time temperature reached extreme values (+32 and +20 °C, respectively), with 31.0% extra deaths for periods of three days or more. Heat during summer 2015 was associated with an increase in mortality in the warmer regions of Switzerland and it mainly affected older people. Estimates for 2015 were only a little lower compared to those of summer 2003, indicating that mitigation measures to prevent heat-related mortality in Switzerland have not become noticeably effective in the last 10 years.

Effects of elevated summer temperatures and reduced pH on metabolism and growth of juvenile trout (Oncorhynchus mykiss) on unlimited ration

International Nuclear Information System (INIS)

Dockray, J.J.; Reid, S.D.; Wood, C.M.

1996-01-01

Juvenile trout (Oncorhynchus mykiss) were exposed to a simulated global warming - acidic water scenario over a 90-day summer period (control temperature range 13-24 o C). The addition of 2 o C to the fluctuating summer cycle of inshore Lake Ontario and H 2 SO 4 to synthetic soft water resulted in four treatments: control, acidification of control, simulated global warming alone, and global warming plus acidification. The twice-daily feeding regime raised metabolic rates to ∼75% of MO 2 (max). Large increases (from 4.5 to 11.5%) in whole-body lipid, smaller increases (from 12.0 to 15.5%) in protein, and compensating decreases in water content (from 77 to 71%) occurred in all treatments over time. The addition of 2 o C resulted in depressed appetites and growth, particularly after the period of peak temperature (days 60-90; 26 o C). Metabolic rate and nitrogenous waste excretion were also depressed. Overall, exposure to low pH resulted in increased appetites and growth, the increase of 2 o C reduced gross energy intake and increased fecal energy losses, and exposure to low pH resulted in increased energy intake and gain and better conversion efficiency. The lack of ionregulatory disturbance in trout chronically exposed to pH 5.2 suggested that dietary NaCl may have compensated for branchial ion losses. (author). 63 refs., 5 tabs., 4 figs

Warm water temperatures and shifts in seasonality increase trout recruitment but only moderately decrease adult size in western North American tailwaters

Science.gov (United States)

Dibble, Kimberly L.; Yackulic, Charles B.; Kennedy, Theodore A.

2018-01-01

Dams throughout western North America have altered thermal regimes in rivers, creating cold, clear “tailwaters” in which trout populations thrive. Ongoing drought in the region has led to highly publicized reductions in reservoir storage and raised concerns about potential reductions in downstream flows. Large changes in riverine thermal regimes may also occur as reservoir water levels drop, yet this potential impact has received far less attention. We analyzed historic water temperature and fish population data to anticipate how trout may respond to future changes in the magnitude and seasonality of river temperatures. We found that summer temperatures were inversely related to reservoir water level, with warm temperatures associated with reduced storage and with dams operated as run-of-river units. Variation in rainbow trout (Oncorhynchus mykiss) recruitment was linked to water temperature variation, with a 5-fold increase in recruitment occurring at peak summer temperatures (18 °C vs. 7 °C) and a 2.5-fold increase in recruitment when peak temperatures occurred in summer rather than fall. Conversely, adult trout size was only moderately related to temperature. Rainbow and brown trout (Salmo trutta) size decreased by ~24 mm and 20 mm, respectively, as mean annual and peak summer temperatures increased. Further, rainbow trout size decreased by ~29 mm with an earlier onset of cold winter temperatures. While increased recruitment may be the more likely outcome of a warmer and drier climate, density-dependent growth constraints could exacerbate temperature-dependent growth reductions. As such, managers may consider implementing flows to reduce recruitment or altering infrastructure to maintain coldwater reservoir releases.

Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

Science.gov (United States)

Liu, Jiawei; Xu, Haiming; Deng, Jiechun

2018-04-01

Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 °C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM) intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 °C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR) method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30-40° N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH) and a southward shift of the East Asian subtropical jet (EASJ), which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 °C warming. Corrected EASM intensity exhibits a slight difference between 1.5 and 2 °C, but a

Summer temperatures in the Canadian Rockies during the last millennium: a revised record

Energy Technology Data Exchange (ETDEWEB)

Luckman, B.H. [University of Western Ontario, Department of Geography, London, Ontario (Canada); Wilson, R.J.S. [Edinburgh University, School of GeoSciences, Grant Institute, Edinburgh (United Kingdom)

2005-02-01

We present a significant update to a millennial summer temperature reconstruction (1073-1983) that was originally published in 1997. Utilising new tree-ring data (predominantly Picea engelmannii), the reconstruction is not only better replicated, but has been extended (950-1994) and is now more regionally representative. Calibration and verification statistics were improved, with the new model explaining 53% of May-August maximum temperature variation compared to the original (39% of April-August mean temperatures). The maximum latewood density data, which are weighted more strongly in the regression model than ringwidth, were processed using regional curve standardisation to capture potential centennial to millennial scale variability. The reconstruction shows warm intervals, comparable to twentieth century values, for the first half of the eleventh century, the late 1300s and early 1400s. The bulk of the record, however, is below the 1901-1980 normals, with prolonged cool periods from 1200 to 1350 and from 1450 to the late 19th century. The most extreme cool period is observed to be in the 1690s. These reconstructed cool periods compare well with known regional records of glacier advances between 1150 and the 1300s, possibly in the early 1500s, early 1700s and 1800s. Evidence is also presented of the influence of solar activity and volcanic events on summer temperature in the Canadian Rockies over the last 1,000 years. Although this reconstruction is regional in scope, it compares well at multi-decadal to centennial scales with Northern Hemisphere temperature proxies and at millennial scales with reconstructions that were also processed to capture longer timescale variability. This coherence suggests that this series is globally important for the assessment of natural temperature variability over the last 1,000 years. (orig.)

Common Warm Dust Temperatures Around Main Sequence Stars

Science.gov (United States)

Morales, Farisa; Rieke, George; Werner, Michael; Stapelfeldt, Karl; Bryden, Geoffrey; Su, Kate

2011-01-01

We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-KO) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (∼ 190 K and ∼60 K for the inner and outer dust components, respectively)-slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at ∼ 150 K can deposit particles into an inner/warm belt, where the small grains are heated to dust Temperatures of -190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-KO stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon.

Terrestrial carbon cycle affected by non-uniform climate warming

International Nuclear Information System (INIS)

Jianyang Xia; Yiqi Luo; Jiquan Chen; Shilong Piao; Ciais, Philippe; Shiqiang Wan

2014-01-01

Feedbacks between the terrestrial carbon cycle and climate change could affect many ecosystem functions and services, such as food production, carbon sequestration and climate regulation. The rate of climate warming varies on diurnal and seasonal timescales. A synthesis of global air temperature data reveals a greater rate of warming in winter than in summer in northern mid and high latitudes, and the inverse pattern in some tropical regions. The data also reveal a decline in the diurnal temperature range over 51% of the global land area and an increase over only 13%, because night-time temperatures in most locations have risen faster than daytime temperatures. Analyses of satellite data, model simulations and in situ observations suggest that the impact of seasonal warming varies between regions. For example, spring warming has largely stimulated ecosystem productivity at latitudes between 30 degrees and 90 degrees N, but suppressed productivity in other regions. Contrasting impacts of day- and night-time warming on plant carbon gain and loss are apparent in many regions. We argue that ascertaining the effects of non-uniform climate warming on terrestrial ecosystems is a key challenge in carbon cycle research. (authors)

LHC Report: Summer temperatures in the LHC

CERN Multimedia

Jan Uythoven for the LHC Team

2012-01-01

The LHC experiments have finished their data-taking period before the summer conferences. The machine has already delivered substantially more collisions to the experiments this year than in the whole of 2011. The LHC has now started a six-day Machine Development period, which will be followed by the second Technical Stop of the year.   The number of collisions delivered to the experiments is expressed in integrated luminosity. In 2011, the integrated luminosity delivered to both ATLAS and CMS was around 5.6 fb-1. On Monday 18 June, experiments finished taking data before the summer conferences and the integrated luminosity for 2012 so far is about 6.6 fb-1, well above the unofficial target of 5 fb-1. The LHC’s performance over the last week of running was so efficient that the injection kicker magnets – which heat up due to the circulating beam – did not have time to cool down between the subsequent fills. As the time constants for warming up and cooli...

Influence of Flow Regulation on Summer Water Temperature: Sauce Grande River, Argentina

Science.gov (United States)

Casado, A.; Hannah, D. M.; Peiry, J.; Campo, A. M.

2012-12-01

This study quantifies the effects of the Paso de las Piedras Dam on the thermal behaviour of the Sauce Grande River, Argentina, during a summer season. A 30-day data set of continuous hourly data was assembled for eight stream temperature gauging sites deployed above and below the impoundment. Time series span the hottest period recorded during summer 2009 to evaluate variations in river water temperature under strong meteorological influence. The methods include: (i) analysis of the time series by inspecting the absolute differences in daily data (magnitude, timing, frequency, duration and rate of change), (ii) classification of diurnal regimes by using a novel regime 'shape' and 'magnitude' classifying method (RSMC), and (ii) quantification of the sensitivity of water temperature regimes to air temperature by computation of a novel sensitivity index (SI). Results showed that fluctuations in daily water temperatures were linked to meteorological drivers; however, spatial variability in the shape and the magnitude of the thermographs revealed the effects of the impoundment in regulating the thermal behaviour of the river downstream. An immediate cooling effect below the dam was evident. Mean daily temperatures were reduced in up to 4 °C, and described a warming trend in the downstream direction over a distance of at least 15 km (up to +2.3 °C). Diurnal cycles were reduced in amplitude and delayed in timing, and revealed a dominance of regime magnitude stability and regime shape climatic insensitivity over a distance of 8 km downstream. These findings provide new information about the water quality of the Sauce Grande River and inform management of flows to maintain the ecological integrity of the river system. Also, they motivate further analysis of potential correlates under varying hydrological and meteorological conditions. The methods presented herein have wider applicability for quantifying river thermal regimes and their sensitivity to climate and other

Effects of forest harvesting on summer stream temperatures in New Brunswick, Canada: an inter-catchment, multiple-year comparison

Directory of Open Access Journals (Sweden)

C. P.-A. Bourque

2001-01-01

Full Text Available This paper presents a pre- and post-harvest comparison of stream temperatures collected in five neighbouring streams (sub-catchments over a period of five years (1994-1998. The aim of the study was to determine whether land cover changes from clear cutting in areas outside forest buffer zones (applied to streams >0.5 m wide might contribute to an increase in summer mean stream temperatures in buffered streams downslope by infusion of warmed surface and sub-surface water into the streams. Specific relationships were observed in all five forest streams investigated. To assist in the analysis, several spatially-relevant variables, such as land cover change, mid-summer potential solar radiation, flow accumulation, stream location and slope of the land were determined, in part, from existing aerial photographs, GIS-archived forest inventory data and a digital terrain model of the study area. Spatial calculations of insolation levels for July 15th were used as an index of mid-summer solar heating across sub-catchments. Analysis indicated that prior to the 1995 harvest, differences in stream temperature could be attributed to (i topographic position and catchment-to-sun orientation, (ii the level of cutting that occurred in the upper catchment prior to the start of the study, and (iii the average slope within harvested areas. Compared to the pre-harvest mean stream temperatures in 1994, mean temperatures in the three streams downslope from the 1995 harvest areas increased by 0.3 to 0.7°C (representing a 4-8% increase; p-value of normalised temperatures Keywords: terrain attributes, solar radiation, land cover, forest buffers, New Brunswick regulations, spatial modelling, DEM, forest covertypes

Warm summer nights and the growth decline of shore pine in Southeast Alaska

Science.gov (United States)

Sullivan, Patrick F.; Mulvey, Robin L.; Brownlee, Annalis H.; Barrett, Tara M.; Pattison, Robert R.

2015-12-01

Shore pine, which is a subspecies of lodgepole pine, was a widespread and dominant tree species in Southeast Alaska during the early Holocene. At present, the distribution of shore pine in Alaska is restricted to coastal bogs and fens, likely by competition with Sitka spruce and Western hemlock. Monitoring of permanent plots as part of the United States Forest Service Forest Inventory and Analysis program identified a recent loss of shore pine biomass in Southeast Alaska. The apparent loss of shore pine is concerning, because its presence adds a vertical dimension to coastal wetlands, which are the richest plant communities of the coastal temperate rainforest in Alaska. In this study, we examined the shore pine tree-ring record from a newly established plot network throughout Southeast Alaska and explored climate-growth relationships. We found a steep decline in shore pine growth from the early 1960s to the present. Random Forest regression revealed a strong correlation between the decline in shore pine growth and the rise in growing season diurnal minimum air temperature. Warm summer nights, cool daytime temperatures and a reduced diurnal temperature range are associated with greater cloud cover in Southeast Alaska. This suite of conditions could lead to unfavorable tree carbon budgets (reduced daytime photosynthesis and greater nighttime respiration) and/or favor infection by foliar pathogens, such as Dothistroma needle blight, which has recently caused widespread tree mortality on lodgepole pine plantations in British Columbia. Further field study that includes experimental manipulation (e.g., fungicide application) will be necessary to identify the proximal cause(s) of the growth decline. In the meantime, we anticipate continuation of the shore pine growth decline in Southeast Alaska.

A 400-year ice core melt layer record of summertime warming in the Alaska Range

Science.gov (United States)

Winski, D.; Osterberg, E. C.; Kreutz, K. J.; Wake, C. P.; Ferris, D. G.; Campbell, S. W.; Baum, M.; Raudzens Bailey, A.; Birkel, S. D.; Introne, D.; Handley, M.

2017-12-01

Warming in high-elevation regions has socially relevant impacts on glacier mass balance, water resources, and sensitive alpine ecosystems, yet very few high-elevation temperature records exist from the middle or high latitudes. While many terrestrial paleoclimate records provide critical temperature records from low elevations over recent centuries, melt layers preserved in alpine glaciers present an opportunity to develop calibrated, annually-resolved temperature records from high elevations. We present a 400-year temperature record based on the melt-layer stratigraphy in two ice cores collected from Mt. Hunter in the Central Alaska Range. The ice core record shows a 60-fold increase in melt frequency and water equivalent melt thickness between the pre-industrial period (before 1850) and present day. We calibrate the melt record to summer temperatures based on local and regional weather station analyses, and find that the increase in melt production represents a summer warming of at least 2° C, exceeding rates of temperature increase at most low elevation sites in Alaska. The Mt. Hunter melt layer record is significantly (p<0.05) correlated with surface temperatures in the central tropical Pacific through a Rossby-wave like pattern that induces high temperatures over Alaska. Our results show that rapid alpine warming has taken place in the Alaska Range for at least a century, and that conditions in the tropical oceans contribute to this warming.

Eutrophication and Warming Boost Cyanobacterial Biomass and Microcystins

Directory of Open Access Journals (Sweden)

Miquel Lürling

2017-02-01

Full Text Available Eutrophication and warming are key drivers of cyanobacterial blooms, but their combined effects on microcystin (MC concentrations are less studied. We tested the hypothesis that warming promotes cyanobacterial abundance in a natural plankton community and that eutrophication enhances cyanobacterial biomass and MC concentrations. We incubated natural seston from a eutrophic pond under normal, high, and extreme temperatures (i.e., 20, 25, and 30 °C with and without additional nutrients added (eutrophication mimicking a pulse as could be expected from projected summer storms under climate change. Eutrophication increased algal- and cyanobacterial biomass by 26 and 8 times, respectively, and led to 24 times higher MC concentrations. This effect was augmented with higher temperatures leading to 45 times higher MC concentrations at 25 °C, with 11 times more cyanobacterial chlorophyll-a and 25 times more eukaryote algal chlorophyll-a. At 30 °C, MC concentrations were 42 times higher, with cyanobacterial chlorophyll-a being 17 times and eukaryote algal chlorophyll-a being 24 times higher. In contrast, warming alone did not yield more cyanobacteria or MCs, because the in situ community had already depleted the available nutrient pool. MC per potential MC producing cell declined at higher temperatures under nutrient enrichments, which was confirmed by a controlled experiment with two laboratory strains of Microcystis aeruginosa. Nevertheless, MC concentrations were much higher at the increased temperature and nutrient treatment than under warming alone due to strongly promoted biomass, lifting N-imitation and promotion of potential MC producers like Microcystis. This study exemplifies the vulnerability of eutrophic urban waters to predicted future summer climate change effects that might aggravate cyanobacterial nuisance.

Global temperatures and the global warming ``debate''

Science.gov (United States)

Aubrecht, Gordon

2009-04-01

Many ordinary citizens listen to pronouncements on talk radio casting doubt on anthropogenic global warming. Some op-ed columnists likewise cast doubts, and are read by credulous citizens. For example, on 8 March 2009, the Boston Globe published a column by Jeff Jacoby, ``Where's global warming?'' According to Jacoby, ``But it isn't such hints of a planetary warming trend that have been piling up in profusion lately. Just the opposite.'' He goes on to write, ``the science of climate change is not nearly as important as the religion of climate change,'' and blamed Al Gore for getting his mistaken views accepted. George Will at the Washington Post also expressed denial. As a result, 44% of U.S. voters, according to the January 19 2009 Rasmussen Report, blame long-term planetary trends for global warming, not human beings. Is there global cooling, as skeptics claim? We examine the temperature record.

The Interdecadal Variability of Summer Precipitation over the South of China and its Response to Asian Monsoon at the Turning Points of Global Warming

Science.gov (United States)

Wang, Huan; Li, Dongliang

2017-04-01

Under the background of global warming, decadal variability of the summer precipitation in the South of China and the Asian monsoon experienced mutations at around the end of 1970s, the beginning of 1990s and 21st century. We examined the external and internal forcings which may cause the mutations and diagnosed the mechanism. Human emission of CO2 has always been the fatal reason for global warming, and it is also the primary reason for the precipitation increasing over Yangtze-Huai river basin at the end of the 1970s. The Yangtze-Huai river basin and South China demonstrated more summer rainfall after 1993. This can be explained by the weakening of the Asian summer monsoon caused by the positive anomaly of summer SST over northwest Pacific Ocean and Indian Ocean. A significant trend in the enhancement of sensible heat over the TP has exerted some considerable influence on the reinforce of the EASM, accompanied by the northward migration of the summer precipitation belt shifting northward at the beginning of 21st century.

The Role of Atmospheric Heating over the South China Sea and Western Pacific Regions in Modulating Asian Summer Climate under the Global Warming Background

Science.gov (United States)

He, B.

2015-12-01

Global warming is one of the most significant climate change signals at the earth's surface. However, the responses of monsoon precipitation to global warming show very distinct regional features, especially over the South China Sea (SCS) and surrounding regions during boreal summer. To understand the possible dynamics in these specific regions under the global warming background, the changes in atmospheric latent heating and their possible influences on global climate are investigated by both observational diagnosis and numerical sensitivity simulations. Results indicate that summertime latent heating has intensified in the SCS and western Pacific, accompanied by increased precipitation, cloud cover, lower-tropospheric convergence, and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS-western Pacific and South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia and leading to a warm and dry climate. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The results highlight the important role of latent heating in adjusting the changes in sea surface temperature through atmospheric dynamics.

Consequences of Global Warming of 1.5 °C and 2 °C for Regional Temperature and Precipitation Changes in the Contiguous United States.

Science.gov (United States)

Karmalkar, Ambarish V; Bradley, Raymond S

2017-01-01

The differential warming of land and ocean leads to many continental regions in the Northern Hemisphere warming at rates higher than the global mean temperature. Adaptation and conservation efforts will, therefore, benefit from understanding regional consequences of limiting the global mean temperature increase to well below 2°C above pre-industrial levels, a limit agreed upon at the United Nations Climate Summit in Paris in December 2015. Here, we analyze climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to determine the timing and magnitude of regional temperature and precipitation changes across the contiguous United States (US) for global warming of 1.5 and 2°C and highlight consensus and uncertainties in model projections and their implications for making decisions. The regional warming rates differ considerably across the contiguous US, but all regions are projected to reach 2°C about 10-20 years before the global mean temperature. Although there is uncertainty in the timing of exactly when the 1.5 and 2°C thresholds will be crossed regionally, over 80% of the models project at least 2°C warming by 2050 for all regions for the high emissions scenario. This threshold-based approach also highlights regional variations in the rate of warming across the US. The fastest warming region in the contiguous US is the Northeast, which is projected to warm by 3°C when global warming reaches 2°C. The signal-to-noise ratio calculations indicate that the regional warming estimates remain outside the envelope of uncertainty throughout the twenty-first century, making them potentially useful to planners. The regional precipitation projections for global warming of 1.5°C and 2°C are uncertain, but the eastern US is projected to experience wetter winters and the Great Plains and the Northwest US are projected to experience drier summers in the future. The impact of different scenarios on regional precipitation projections is

Spatio-Temporal Characteristics of Global Warming in the Tibetan Plateau during the Last 50 Years Based on a Generalised Temperature Zone - Elevation Model

Science.gov (United States)

Wei, Yanqiang; Fang, Yiping

2013-01-01

Temperature is one of the primary factors influencing the climate and ecosystem, and examining its change and fluctuation could elucidate the formation of novel climate patterns and trends. In this study, we constructed a generalised temperature zone elevation model (GTEM) to assess the trends of climate change and temporal-spatial differences in the Tibetan Plateau (TP) using the annual and monthly mean temperatures from 1961–2010 at 144 meteorological stations in and near the TP. The results showed the following: (1) The TP has undergone robust warming over the study period, and the warming rate was 0.318°C/decade. The warming has accelerated during recent decades, especially in the last 20 years, and the warming has been most significant in the winter months, followed by the spring, autumn and summer seasons. (2) Spatially, the zones that became significantly smaller were the temperature zones of −6°C and −4°C, and these have decreased 499.44 and 454.26 thousand sq km from 1961 to 2010 at average rates of 25.1% and 11.7%, respectively, over every 5-year interval. These quickly shrinking zones were located in the northwestern and central TP. (3) The elevation dependency of climate warming existed in the TP during 1961–2010, but this tendency has gradually been weakening due to more rapid warming at lower elevations than in the middle and upper elevations of the TP during 1991–2010. The higher regions and some low altitude valleys of the TP were the most significantly warming regions under the same categorizing criteria. Experimental evidence shows that the GTEM is an effective method to analyse climate changes in high altitude mountainous regions. PMID:23565182

Historical ablation rates on south-east Greenland glaciers measured in the 1933 warm summer

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Bent Hasholt

2016-07-01

Full Text Available Ice ablation rates measured on four glaciers in south-east Greenland in summer 1933 are recovered from an old field book of geologist K. Milthers. These unpublished ablation data are among the first measured in Greenland and were obtained during a warm period comparable to that of recent years. Ablation rates of up to 45 mm ice eq. d−1 were observed. Using the Tasiilaq meteorological record, we calculate degree-day factors of ca. 3–5 mm ice eq. d−1°C−1. Comparing these results with 1996–2012 observations at one of Milthers’ glaciers (Mittivakkat, we find that ablation rates and degree-day factors are significantly higher (61±50% in recent years. We speculate this to be due to a reduction in surface albedo, and perhaps the retreat of the glaciers out of the cold maritime inversion layer. Our findings suggest that using a temperature-index method that assumes constant degree-day factors may produce inaccurate long-term ablation estimates for south-east Greenland glaciers, further emphasizing the value of the rare 1933 measurements for validation of ablation models.

Regional patterns of increasing Swiss needle cast impacts on Douglas-fir growth with warming temperatures.

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Lee, E Henry; Beedlow, Peter A; Waschmann, Ronald S; Tingey, David T; Cline, Steven; Bollman, Michael; Wickham, Charlotte; Carlile, Cailie

2017-12-01

The fungal pathogen, Phaeocryptopus gaeumannii , causing Swiss needle cast (SNC) occurs wherever Douglas-fir is found but disease damage is believed to be limited in the U.S. Pacific Northwest (PNW) to the Coast Range of Oregon and Washington (Hansen et al., Plant Disease , 2000, 84 , 773; Rosso & Hansen, Phytopathology , 2003, 93 , 790; Shaw, et al., Journal of Forestry , 2011, 109 , 109). However, knowledge remains limited on the history and spatial distribution of SNC impacts in the PNW. We reconstructed the history of SNC impacts on mature Douglas-fir trees based on tree-ring width chronologies from western Oregon. Our findings show that SNC impacts on growth occur wherever Douglas-fir is found and is not limited to the coastal fog zone. The spatiotemporal patterns of growth impact from SNC disease were synchronous across the region, displayed periodicities of 12-40 years, and strongly correlated with winter and summer temperatures and summer precipitation. The primary climatic factor limiting pathogen dynamics varied spatially by location, topography, and elevation. SNC impacts were least severe in the first half of the 20th century when climatic conditions during the warm phase of the Pacific Decadal Oscillation (1924-1945) were less conducive to pathogen development. At low- to mid-elevations, SNC impacts were most severe in 1984-1986 following several decades of warmer winters and cooler, wetter summers including a high summer precipitation anomaly in 1983. At high elevations on the west slope of the Cascade Range, SNC impacts peaked several years later and were the greatest in the 1990s, a period of warmer winter temperatures. Climate change is predicted to result in warmer winters and will likely continue to increase SNC severity at higher elevations, north along the coast from northern Oregon to British Columbia, and inland where low winter temperatures currently limit growth of the pathogen. Our findings indicate that SNC may become a significant

Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

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J. Liu

2018-04-01

Full Text Available Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 °C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 °C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30–40° N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH and a southward shift of the East Asian subtropical jet (EASJ, which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 °C warming. Corrected EASM intensity exhibits a slight difference

Native temperature regime influences soil response to simulated warming

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Timothy G. Whitby; Michael D. Madritch

2013-01-01

Anthropogenic climate change is expected to increase global temperatures and potentially increase soil carbon (C) mineralization, which could lead to a positive feedback between global warming and soil respiration. However the magnitude and spatial variability of belowground responses to warming are not yet fully understood. Some of the variability may depend...

Temperature and ice layer trends in the summer middle atmosphere

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Lübken, F.-J.; Berger, U.

2012-04-01

We present results from our LIMA model (Leibniz Institute Middle Atmosphere Model) which nicely reproduces mean conditions of the summer mesopause region and also mean characteristics of ice layers known as noctilucent clouds. LIMA nudges to ECMWF data in the troposphere and lower stratosphere which influences the background conditions in the mesosphere. We study temperature trends in the mesosphere at middle and polar latitudes and compared with temperature trends from satellites, lidar, and phase height observations. For the first time large observed temperature trends in the summer mesosphere can be reproduced and explained by a model. As will be shown, stratospheric ozone has a major impact on temperature trends in the summer mesosphere. The temperature trend is not uniform in time: it is moderate from 1961 (the beginning of our record) until the beginning of the 1980s. Thereafter, temperatures decrease much stronger until the mid 1990s. Thereafter, temperatures are nearly constant or even increase with time. As will be shown, trends in ozone and carbon dioxide explain most of this behavior. Ice layers in the summer mesosphere are very sensitive to background conditions and are therefore considered to be appropriate tracers for long term variations in the middle atmosphere. We use LIMA background conditions to determine ice layer characteristics in the mesopause region. We compare our results with measurements, for example with albedos from the SBUV satellites, and show that we can nicely reproduce observed trends. It turns out that temperature trends are positive (negative) in the upper (lower) part of the ice layer regime. This complicates an interpretation of NLC long term variations in terms of temperature trends.

Long-term responses of the endemic reef-builder Cladocora caespitosa to Mediterranean warming.

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Diego K Kersting

Full Text Available Recurrent climate-induced mass-mortalities have been recorded in the Mediterranean Sea over the past 15 years. Cladocora caespitosa, the sole zooxanthellate scleractinian reef-builder in the Mediterranean, is among the organisms affected by these episodes. Extensive bioconstructions of this endemic coral are very rare at the present time and are threatened by several stressors. In this study, we assessed the long-term response of this temperate coral to warming sea-water in the Columbretes Islands (NW Mediterranean and described, for the first time, the relationship between recurrent mortality events and local sea surface temperature (SST regimes in the Mediterranean Sea. A water temperature series spanning more than 20 years showed a summer warming trend of 0.06°C per year and an increased frequency of positive thermal anomalies. Mortality resulted from tissue necrosis without massive zooxanthellae loss and during the 11-year study, necrosis was recorded during nine summers separated into two mortality periods (2003-2006 and 2008-2012. The highest necrosis rates were registered during the first mortality period, after the exceptionally hot summer of 2003. Although necrosis and temperature were significantly associated, the variability in necrosis rates during summers with similar thermal anomalies pointed to other acting factors. In this sense, our results showed that these differences were more closely related to the interannual temperature context and delayed thermal stress after extreme summers, rather than to acclimatisation and adaption processes.

Observed 1970-2005 cooling of summer daytime temperatures in coastal California

Energy Technology Data Exchange (ETDEWEB)

Lebassi, B.; Gonzalez, J.; Fabris, D.; Maurer, E.; Miller, N.; Milesi, C.; Bornstein, R.

2009-05-15

The study evaluated 1948-2004 summer (JJA) mean monthly air temperatures for two California air basins: SoCAB and SFBA. The study focuses on the more rapid post-1970 warming period, and its daily T{sub min} and T{sub max} values were used to produce average monthly values and spatial distributions of trends for each air basins. Additional analyses included T{sub D} values at two NWS sites, SSTs, NCEP reanalysis sea-level pressures, and GCM T{sub ave}-values. Results for all California COOP sites together showed increased JJA T{sub ave}-values; asymmetric warming, as T{sub min}-values increase faster than T{sub max}-values; and thus decreased DTR values. The spatial distribution of observed SoCAB and SFBA T{sub max} values exhibited a complex pattern, with cooling in low-elevation coastal-areas open to marine air penetration and warming at inland areas. Results also showed that decreased DTR values in the valleys arose from small increases at 'inland' sites combined with large decreases at 'coastal' sites. Previous studies suggest that cooling JJA T{sub max}-values in coastal California were due to increased irrigation, coastal upwelling, or cloud cover, while the current hypothesis is that they arises from GHG-induced global-warming of 'inland' areas, which results in increased sea breeze flow activity. Sea level pressure trends showed increases in the oceanic Pacific High and decreases in the central-California Thermal Low. The corresponding gradient thus showed a trend of 0.02 hPa 100-km{sup -1} decade{sup -1}, supportive of the hypothesis of increased sea breeze activity. Trends in T{sub D} values showed a larger value at coastal SFO than at inland SEC, which indicative of increased sea breeze activity; calculated SST trends (0.15 C decade{sup -1}) could also have increase T{sub D}-values. GCM model Tave-values showed warming that decreases from 0.13 C decade{sup -1} at inland California to 0.08 C decade{sup -1} at coastal areas

Extreme Temperature Exceedances Change more Rapidly Under Future Warming in Regions of non-Gaussian Short Temperature Distribution Tails

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Loikith, P. C.; Neelin, J. D.; Meyerson, J.

2017-12-01

Regions of shorter-than-Gaussian warm and cold side temperature distribution tails are shown to occur in spatially coherent patterns in the current climate. Under such conditions, warming may be manifested in more complex ways than if the underlying distribution were close to Gaussian. For example, under a uniform warm shift, the simplest prototype for future warming, a location with a short warm side tail would experience a greater increase in extreme warm exceedances compared to if the distribution were Gaussian. Similarly, for a location with a short cold side tail, a uniform warm shift would result in a rapid decrease in extreme cold exceedances. Both scenarios carry major societal and environmental implications including but not limited to negative impacts on human and ecosystem health, agriculture, and the economy. It is therefore important for climate models to be able to realistically reproduce short tails in simulations of historical climate in order to boost confidence in projections of future temperature extremes. Overall, climate models contributing to the fifth phase of the Coupled Model Intercomparison Project capture many of the principal observed regions of short tails. This suggests the underlying dynamics and physics occur on scales resolved by the models, and helps build confidence in model projections of extremes. Furthermore, most GCMs show more rapid changes in exceedances of extreme temperature thresholds in regions of short tails. Results therefore suggest that the shape of the tails of the underlying temperature distribution is an indicator of how rapidly a location will experience changes to extreme temperature occurrence under future warming.

Global patterns in lake ecosystem responses to warming based on the temperature dependence of metabolism.

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Kraemer, Benjamin M; Chandra, Sudeep; Dell, Anthony I; Dix, Margaret; Kuusisto, Esko; Livingstone, David M; Schladow, S Geoffrey; Silow, Eugene; Sitoki, Lewis M; Tamatamah, Rashid; McIntyre, Peter B

2017-05-01

Climate warming is expected to have large effects on ecosystems in part due to the temperature dependence of metabolism. The responses of metabolic rates to climate warming may be greatest in the tropics and at low elevations because mean temperatures are warmer there and metabolic rates respond exponentially to temperature (with exponents >1). However, if warming rates are sufficiently fast in higher latitude/elevation lakes, metabolic rate responses to warming may still be greater there even though metabolic rates respond exponentially to temperature. Thus, a wide range of global patterns in the magnitude of metabolic rate responses to warming could emerge depending on global patterns of temperature and warming rates. Here we use the Boltzmann-Arrhenius equation, published estimates of activation energy, and time series of temperature from 271 lakes to estimate long-term (1970-2010) changes in 64 metabolic processes in lakes. The estimated responses of metabolic processes to warming were usually greatest in tropical/low-elevation lakes even though surface temperatures in higher latitude/elevation lakes are warming faster. However, when the thermal sensitivity of a metabolic process is especially weak, higher latitude/elevation lakes had larger responses to warming in parallel with warming rates. Our results show that the sensitivity of a given response to temperature (as described by its activation energy) provides a simple heuristic for predicting whether tropical/low-elevation lakes will have larger or smaller metabolic responses to warming than higher latitude/elevation lakes. Overall, we conclude that the direct metabolic consequences of lake warming are likely to be felt most strongly at low latitudes and low elevations where metabolism-linked ecosystem services may be most affected. © 2016 John Wiley & Sons Ltd.

Assessing water quality of the Chesapeake Bay by the impact of sea level rise and warming

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Wang, P.; Linker, L.; Wang, H.; Bhatt, G.; Yactayo, G.; Hinson, K.; Tian, R.

2017-08-01

The influence of sea level rise and warming on circulation and water quality of the Chesapeake Bay under projected climate conditions in 2050 were estimated by computer simulation. Four estuarine circulation scenarios in the estuary were run using the same watershed load in 1991-2000 period. They are, 1) the Base Scenario, which represents the current climate condition, 2) a Sea Level Rise Scenario, 3) a Warming Scenario, and 4) a combined Sea Level Rise and Warming Scenario. With a 1.6-1.9°C increase in monthly air temperatures in the Warming Scenario, water temperature in the Bay is estimated to increase by 0.8-1°C. Summer average anoxic volume is estimated to increase 1.4 percent compared to the Base Scenario, because of an increase in algal blooms in the spring and summer, promotion of oxygen consumptive processes, and an increase of stratification. However, a 0.5-meter Sea Level Rise Scenario results in a 12 percent reduction of anoxic volume. This is mainly due to increased estuarine circulation that promotes oxygen-rich sea water intrusion in lower layers. The combined Sea Level Rise and Warming Scenario results in a 10.8 percent reduction of anoxic volume. Global warming increases precipitation and consequently increases nutrient loads from the watershed by approximately 5-7 percent. A scenario that used a 10 percent increase in watershed loads and current estuarine circulation patterns yielded a 19 percent increase in summer anoxic volume, while a scenario that used a 10 percent increase in watershed loads and modified estuarine circulation patterns by the aforementioned sea level rise and warming yielded a 6 percent increase in summer anoxic volume. Impacts on phytoplankton, sediments, and water clarity were also analysed.

Relationships between declining summer sea ice, increasing temperatures and changing vegetation in the Siberian Arctic tundra from MODIS time series (2000–11)

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Dutrieux, L P; Bartholomeus, H; Herold, M; Verbesselt, J

2012-01-01

The concern about Arctic greening has grown recently as the phenomenon is thought to have significant influence on global climate via atmospheric carbon emissions. Earlier work on Arctic vegetation highlighted the role of summer sea ice decline in the enhanced warming and greening phenomena observed in the region, but did not contain enough details for spatially characterizing the interactions between sea ice, temperature and vegetation photosynthetic absorption. By using 1 km resolution data from the Moderate Resolution Imaging Spectrometer (MODIS) as a primary data source, this study presents detailed maps of vegetation and temperature trends for the Siberian Arctic region, using the time integrated normalized difference vegetation index (TI-NDVI) and summer warmth index (SWI) calculated for the period 2000–11 to represent vegetation greenness and temperature respectively. Spatio-temporal relationships between the two indices and summer sea ice conditions were investigated with transects at eight locations using sea ice concentration data from the Special Sensor Microwave/Imager (SSM/I). In addition, the derived vegetation and temperature trends were compared among major Arctic vegetation types and bioclimate subzones. The fine resolution trend map produced confirms the overall greening (+1% yr −1 ) and warming (+0.27% yr −1 ) of the region, reported in previous studies, but also reveals browning areas. The causes of such local decreases in vegetation, while surrounding areas are experiencing the opposite reaction to changing conditions, are still unclear. Overall correlations between sea ice concentration and SWI as well as TI-NDVI decreased in strength with increasing distance from the coast, with a particularly pronounced pattern in the case of SWI. SWI appears to be driving TI-NDVI in many cases, but not systematically, highlighting the presence of limiting factors other than temperature for plant growth in the region. Further unravelling those limiting

European summer temperatures since Roman times

Czech Academy of Sciences Publication Activity Database

Luterbacher, J.; Werner, J. P.; Smerdon, J. E.; Fernandez-Donado, L.; González-Rouco, J. F.; Barriopedro, D.; Ljungqvist, F. C.; Büntgen, Ulf; Zorita, E.; Wagner, S.; Esper, J.; McCarroll, D.; Toreti, A.; Frank, D.; Jungclaus, J.; Barriendos, M.; Bertolin, C.; Bothe, O.; Brázdil, Rudolf; Camuffo, D.; Dobrovolný, Petr; Gagen, M.; Garica-Bustamante, E.; Ge, Q.; Gomez-Navarro, J. J.; Guiot, J.; Hao, Z.; Hegerl, G.; Holmgren, K.; Klimenko, V. V.; Martin-Chivelet, J.; Pfister, C.; Roberts, N.; Schindler, A.; Schurer, A.; Solomina, O.; von Gunten, L.; Wahl, E.; Wanner, H.; Wetter, O.; Xoplaki, E.; Yuan, N.; Zanchettin, D.; Zhang, H.; Zerefos, C.

2016-01-01

Roč. 11, č. 2 (2016), č. článku 024001. ISSN 1748-9326 R&D Projects: GA ČR GA13-04291S Institutional support: RVO:67179843 Keywords : reconstructing climate anomalies * high-resolution paleoclimatology * northern-hemisphere temperature * tree-ring chronologies * last 1000 years * volcanic - eruptions * forcing reconstructions * bayesian algorithm * pmip simulations * past millennium * Common Era * heat waves * paleoclimatology * Bayesian hierarchical modelling * European summer temperature reconstruction * ensemble of climate model simulations * Medieval Climate Anomaly Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 4.404, year: 2016

Effect of warm compress application on tissue temperature in healthy dogs.

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Millard, Ralph P; Towle-Millard, Heather A; Rankin, David C; Roush, James K

2013-03-01

To measure the effect of warm compress application on tissue temperature in healthy dogs. 10 healthy mixed-breed dogs. Dogs were sedated with hydromorphone (0.1 mg/kg, IV) and diazepam (0.25 mg/kg, IV). Three 24-gauge thermocouple needles were inserted to a depth of 0.5 cm (superficial), 1.0 cm (middle), and 1.5 cm (deep) into a shaved, lumbar, epaxial region to measure tissue temperature. Warm (47°C) compresses were applied with gravity dependence for periods of 5, 10, and 20 minutes. Tissue temperature was recorded before compress application and at intervals for up to 80 minutes after application. Control data were collected while dogs received identical sedation but with no warm compress. Mean temperature associated with 5 minutes of heat application at the superficial, middle, and deep depths was significantly increased, compared with the control temperature. Application for 10 minutes significantly increased the temperature at all depths, compared with 5 minutes of application. Mean temperature associated with 20 minutes of application was not different at the superficial or middle depths, compared with 10 minutes of application. Temperature at the deep depth associated with 10 minutes of application was significantly higher, compared with 20 minutes of application, but all temperature increases at this depth were minimal. Results suggested that application of a warm compress should be performed for 10 minutes. Changes in temperature at a tissue depth of 1.5 cm were minimal or not detected. The optimal compress temperature to achieve therapeutic benefits was not determined.

Changes in the seasonality of Arctic sea ice and temperature

Science.gov (United States)

Bintanja, R.

2012-04-01

Observations show that the Arctic sea ice cover is currently declining as a result of climate warming. According to climate models, this retreat will continue and possibly accelerate in the near-future. However, the magnitude of this decline is not the same throughout the year. With temperatures near or above the freezing point, summertime Arctic sea ice will quickly diminish. However, at temperatures well below freezing, the sea ice cover during winter will exhibit a much weaker decline. In the future, the sea ice seasonal cycle will be no ice in summer, and thin one-year ice in winter. Hence, the seasonal cycle in sea ice cover will increase with ongoing climate warming. This in itself leads to an increased summer-winter contrast in surface air temperature, because changes in sea ice have a dominant influence on Arctic temperature and its seasonality. Currently, the annual amplitude in air temperature is decreasing, however, because winters warm faster than summer. With ongoing summer sea ice reductions there will come a time when the annual temperature amplitude will increase again because of the large seasonal changes in sea ice. This suggests that changes in the seasonal cycle in Arctic sea ice and temperature are closely, and intricately, connected. Future changes in Arctic seasonality (will) have an profound effect on flora, fauna, humans and economic activities.

Warming and the dependence of limber pine (Pinus flexilis) establishment on summer soil moisture within and above its current elevation range

Science.gov (United States)

Moyes, Andrew B.; Castanha, Cristina; Germino, Matthew J.; Kueppers, Lara M.

2013-01-01

Continued changes in climate are projected to alter the geographic distributions of plant species, in part by affecting where individuals can establish from seed. We tested the hypothesis that warming promotes uphill redistribution of subalpine tree populations by reducing cold limitation at high elevation and enhancing drought stress at low elevation. We seeded limber pine (Pinus flexilis) into plots with combinations of infrared heating and water addition treatments, at sites positioned in lower subalpine forest, the treeline ecotone, and alpine tundra. In 2010, first-year seedlings were assessed for physiological performance and survival over the snow-free growing season. Seedlings emerged in midsummer, about 5–8 weeks after snowmelt. Low temperature was not observed to limit seedling photosynthesis or respiration between emergence and October, and thus experimental warming did not appear to reduce cold limitation at high elevation. Instead, gas exchange and water potential from all sites indicated a prevailing effect of summer moisture stress on photosynthesis and carbon balance. Infrared heaters raised soil growing degree days (base 5 °C, p p 3 m-3 consistently corresponded with moderate and severe indications of drought stress in midday stem water potential, stomatal conductance, photosynthesis, and respiration. Seedling survival was greater in watered plots than in heated plots (p = 0.01), and negatively related to soil growing degree days and duration of exposure to θ 3 m-3 in a stepwise linear regression model (p seasonal moisture stress and high soil surface temperature imposed a strong limitation to limber pine seedling establishment across a broad elevation gradient, including at treeline, and that these limitations are likely to be enhanced by further climate warming.

Role of atmospheric heating over the South China Sea and western Pacific regions in modulating Asian summer climate under the global warming background

Science.gov (United States)

He, Bian; Yang, Song; Li, Zhenning

2016-05-01

The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate.

Sensitivity of summer stream temperatures to climate variability in the Pacific Northwest

Science.gov (United States)

Charles Luce; Brian Staab; Marc Kramer; Seth Wenger; Dan Isaak; Callie McConnell

2014-01-01

Estimating the thermal response of streams to a warming climate is important for prioritizing native fish conservation efforts. While there are plentiful estimates of air temperature responses to climate change, the sensitivity of streams, particularly small headwater streams, to warming temperatures is less well understood. A substantial body of literature correlates...

Causes of model dry and warm bias over central U.S. and impact on climate projections.

Science.gov (United States)

Lin, Yanluan; Dong, Wenhao; Zhang, Minghua; Xie, Yuanyu; Xue, Wei; Huang, Jianbin; Luo, Yong

2017-10-12

Climate models show a conspicuous summer warm and dry bias over the central United States. Using results from 19 climate models in the Coupled Model Intercomparison Project Phase 5 (CMIP5), we report a persistent dependence of warm bias on dry bias with the precipitation deficit leading the warm bias over this region. The precipitation deficit is associated with the widespread failure of models in capturing strong rainfall events in summer over the central U.S. A robust linear relationship between the projected warming and the present-day warm bias enables us to empirically correct future temperature projections. By the end of the 21st century under the RCP8.5 scenario, the corrections substantially narrow the intermodel spread of the projections and reduce the projected temperature by 2.5 K, resulting mainly from the removal of the warm bias. Instead of a sharp decrease, after this correction the projected precipitation is nearly neutral for all scenarios.Climate models repeatedly show a warm and dry bias over the central United States, but the origin of this bias remains unclear. Here the authors associate this bias to precipitation deficits in models and after applying a correction, projected precipitation in this region shows no significant changes.

Consequences of Global Warming of 1.5 °C and 2 °C for Regional Temperature and Precipitation Changes in the Contiguous United States.

Directory of Open Access Journals (Sweden)

Ambarish V Karmalkar

Full Text Available The differential warming of land and ocean leads to many continental regions in the Northern Hemisphere warming at rates higher than the global mean temperature. Adaptation and conservation efforts will, therefore, benefit from understanding regional consequences of limiting the global mean temperature increase to well below 2°C above pre-industrial levels, a limit agreed upon at the United Nations Climate Summit in Paris in December 2015. Here, we analyze climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5 to determine the timing and magnitude of regional temperature and precipitation changes across the contiguous United States (US for global warming of 1.5 and 2°C and highlight consensus and uncertainties in model projections and their implications for making decisions. The regional warming rates differ considerably across the contiguous US, but all regions are projected to reach 2°C about 10-20 years before the global mean temperature. Although there is uncertainty in the timing of exactly when the 1.5 and 2°C thresholds will be crossed regionally, over 80% of the models project at least 2°C warming by 2050 for all regions for the high emissions scenario. This threshold-based approach also highlights regional variations in the rate of warming across the US. The fastest warming region in the contiguous US is the Northeast, which is projected to warm by 3°C when global warming reaches 2°C. The signal-to-noise ratio calculations indicate that the regional warming estimates remain outside the envelope of uncertainty throughout the twenty-first century, making them potentially useful to planners. The regional precipitation projections for global warming of 1.5°C and 2°C are uncertain, but the eastern US is projected to experience wetter winters and the Great Plains and the Northwest US are projected to experience drier summers in the future. The impact of different scenarios on regional precipitation

Lack of cool, not warm, extremes distinguishes late 20th Century climate in 979-year Tasmanian summer temperature reconstruction

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Allen, K. J.; Cook, E. R.; Evans, R.; Francey, R.; Buckley, B. M.; Palmer, J. G.; Peterson, M. J.; Baker, P. J.

2018-03-01

Very few annually resolved millennial-length temperature reconstructions exist for the Southern Hemisphere. Here we present four 979-year reconstructions for southeastern Australia for the austral summer months of December-February. Two of the reconstructions are based on the Australian Water Availability Project dataset and two on the Berkeley Earth Surface Temperature dataset. For each climate data set, one reconstruction is based solely on Lagarostrobos franklinii (restricted reconstructions) while the other is based on multiple Tasmanian conifer species (unrestricted reconstructions). Each reconstruction calibrates ~50-60% of the variance in the temperature datasets depending on the number of tree-ring records available for the reconstruction. We found little difference in the temporal variability of the reconstructions, although extremes are amplified in the restricted reconstructions relative to the unrestricted reconstructions. The reconstructions highlight the occurrence of numerous individual years, especially in the 15th-17th Centuries, for which temperatures were comparable with those of the late 20th Century. The 1950-1999 period, however, stands out as the warmest 50-year period on average for the past 979 years, with a sustained shift away from relatively low mean temperatures, the length of which is unique in the 979-year record. The reconstructions are strongly and positively related to temperatures across the southeast of the Australian continent, negatively related to temperatures in the north and northeast of the continent, and uncorrelated with temperatures in the west. The lack of a strong relationship with temperatures across the continent highlights the necessity of a sub-regional focus for Australasian temperature reconstructions.

Antarctica: Cooling or Warming?

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Bunde, Armin; Ludescher, Josef; Franzke, Christian

2013-04-01

We consider the 14 longest instrumental monthly mean temperature records from the Antarctica and analyse their correlation properties by wavelet and detrended fluctuation analysis. We show that the stations in the western and the eastern part of the Antarctica show significant long-term memory governed by Hurst exponents close to 0.8 and 0.65, respectively. In contrast, the temperature records at the inner part of the continent (South Pole and Vostok), resemble white noise. We use linear regression to estimate the respective temperature differences in the records per decade (i) for the annual data, (ii) for the summer and (iii) for the winter season. Using a recent approach by Lennartz and Bunde [1] we estimate the respective probabilities that these temperature differences can be exceeded naturally without inferring an external (anthropogenic) trend. We find that the warming in the western part of the continent and the cooling at the South Pole is due to a gradually changes in the cold extremes. For the winter months, both cooling and warming are well outside the 95 percent confidence interval, pointing to an anthropogenic origin. In the eastern Antarctica, the temperature increases and decreases are modest and well within the 95 percent confidence interval. [1] S. Lennartz and A. Bunde, Phys. Rev. E 84, 021129 (2011)

Climate extremes in Europe at 1.5 and 2 degrees of global warming

Science.gov (United States)

King, Andrew D.; Karoly, David J.

2017-11-01

There is an international effort to attempt to limit global warming to 1.5 °C above pre-industrial levels, however, there is a lack of quantitative analysis on the benefits of holding global warming to such a level. In this study, coupled climate model simulations are used to form large ensembles of simulated years at 1.5 °C and 2 °C of global warming. These ensembles are used to assess projected changes in the frequency and magnitude of European climate extremes at these warming levels. For example, we find that events similar to the European record hot summer of 2003, which caused tens of thousands of excess deaths, would be very likely at least 24% less frequent in a world at 1.5 °C global warming compared to 2 °C global warming. Under 2 °C of global warming, we could expect such extreme summer temperatures in the historical record to become commonplace, occurring in at least one-in-every-two years. We find that there are very clear benefits to limiting global warming for the European continent, including fewer and less intense heat and rainfall extremes when compared with higher levels of global warming.

Methane Cycling in a Warming Wetland

Science.gov (United States)

Noyce, G. L.; Megonigal, P.; Rich, R.; Kirwan, M. L.; Herbert, E. R.

2017-12-01

Coastal wetlands are global hotspots of carbon (C) storage, but the future of these systems is uncertain. In June 2016, we initiated an in-situ, active, whole-ecosystem warming experiment in the Smithsonian's Global Change Research Wetland to quantify how warming and elevated CO2 affect the stability of coastal wetland soil C pools and contemporary rates of C sequestration. Transects are located in two plant communities, dominated by C3 sedges or C4 grasses. The experiment has a gradient design with air and soil warming treatments ranging from ambient to +5.1 °C and heated plots consistently maintain their target temperature year-round. In April 2017, an elevated CO2 treatment was crossed with temperature in the C3community. Ongoing measurements include soil elevation, C fluxes, porewater chemistry and redox potential, and above- and below-ground growth and biomass. In both years, warming increased methane (CH4) emissions (measured at 3-4 week intervals) from spring through fall at the C3 site, but had little effect on emissions from the C4 site. Winter (Dec-Mar) emissions showed no treatment effect. Stable isotope analysis of dissolved CH4 and DIC also indicated that warming had differing effects on CH4 pathways in the two vegetation communities. To better understand temperature effects on rates of CH4 production and oxidation, 1 m soil cores were collected from control areas of the marsh in summer 2017 and incubated at temperatures ranging from 4 °C to 35 °C. Warming increased CH4 production and oxidation rates in surface samples and oxidation rates in the rooting zone samples from both sites, but temperature responses in deep (1 m) soil samples were minimal. In the surface and rooting zone samples, production rates were also consistently higher in C3 soils compared to C4 soils, but, contrary to our expectations, the temperature response was stronger in the C4 soils. However, oxidation in C3 rooting zone samples did have a strong temperature response. The

Observed and simulated temperature extremes during the recent warming hiatus

International Nuclear Information System (INIS)

Sillmann, Jana; Donat, Markus G; Fyfe, John C; Zwiers, Francis W

2014-01-01

The discrepancy between recent observed and simulated trends in global mean surface temperature has provoked a debate about possible causes and implications for future climate change projections. However, little has been said in this discussion about observed and simulated trends in global temperature extremes. Here we assess trend patterns in temperature extremes and evaluate the consistency between observed and simulated temperature extremes over the past four decades (1971–2010) in comparison to the recent 15 years (1996–2010). We consider the coldest night and warmest day in a year in the observational dataset HadEX2 and in the current generation of global climate models (CMIP5). In general, the observed trends fall within the simulated range of trends, with better consistency for the longer period. Spatial trend patterns differ for the warm and cold extremes, with the warm extremes showing continuous positive trends across the globe and the cold extremes exhibiting a coherent cooling pattern across the Northern Hemisphere mid-latitudes that has emerged in the recent 15 years and is not reproduced by the models. This regional inconsistency between models and observations might be a key to understanding the recent hiatus in global mean temperature warming. (letters)

Trends in continental temperature and humidity directly linked to ocean warming.

Science.gov (United States)

Byrne, Michael P; O'Gorman, Paul A

2018-05-08

In recent decades, the land surface has warmed substantially more than the ocean surface, and relative humidity has fallen over land. Amplified warming and declining relative humidity over land are also dominant features of future climate projections, with implications for climate-change impacts. An emerging body of research has shown how constraints from atmospheric dynamics and moisture budgets are important for projected future land-ocean contrasts, but these ideas have not been used to investigate temperature and humidity records over recent decades. Here we show how both the temperature and humidity changes observed over land between 1979 and 2016 are linked to warming over neighboring oceans. A simple analytical theory, based on atmospheric dynamics and moisture transport, predicts equal changes in moist static energy over land and ocean and equal fractional changes in specific humidity over land and ocean. The theory is shown to be consistent with the observed trends in land temperature and humidity given the warming over ocean. Amplified land warming is needed for the increase in moist static energy over drier land to match that over ocean, and land relative humidity decreases because land specific humidity is linked via moisture transport to the weaker warming over ocean. However, there is considerable variability about the best-fit trend in land relative humidity that requires further investigation and which may be related to factors such as changes in atmospheric circulations and land-surface properties.

The effects of boreal forest expansion on the summer Arctic frontal zone

Energy Technology Data Exchange (ETDEWEB)

Liess, Stefan; Snyder, Peter K.; Harding, Keith J. [University of Minnesota, Department of Soil, Water, and Climate, Saint Paul, MN (United States)

2012-05-15

Over the last 100 years, Arctic warming has resulted in a longer growing season in boreal and tundra ecosystems. This has contributed to a slow northward expansion of the boreal forest and a decrease in the surface albedo. Corresponding changes to the surface and atmospheric energy budgets have contributed to a broad region of warming over areas of boreal forest expansion. In addition, mesoscale and synoptic scale patterns have changed as a result of the excess energy at and near the surface. Previous studies have identified a relationship between the positioning of the boreal forest-tundra ecotone and the Arctic frontal zone in summer. This study examines the climate response to hypothetical boreal forest expansion and its influence on the summer Arctic frontal zone. Using the Weather Research and Forecasting model over the Northern Hemisphere, an experiment was performed to evaluate the atmospheric response to expansion of evergreen and deciduous boreal needleleaf forests into open shrubland along the northern boundary of the existing forest. Results show that the lower surface albedo with forest expansion leads to a local increase in net radiation and an average hemispheric warming of 0.6 C at and near the surface during June with some locations warming by 1-2 C. This warming contributes to changes in the meridional temperature gradient that enhances the Arctic frontal zone and strengthens the summertime jet. This experiment suggests that continued Northern Hemisphere high-latitude warming and boreal forest expansion might contribute to additional climate changes during the summer. (orig.)

Disruption of the European climate seasonal clock in a warming world

Science.gov (United States)

Cattiaux, J.; Cassou, C.

2015-12-01

Strength and inland penetration of the oceanic westerly flow over Europe control a large part of the temperature variability over most of the continent. Reduced westerlies, linked to high-pressure anomalies over Scandinavia, induce cold conditions in winter and warm conditions in summer. Here we propose to define the onset of these two seasons as the calendar day where the daily circulation/temperature relationship over Western Europe switches sign. According to this meteorologically-based metrics assessed from several observational datasets, we provide robust evidence for an earlier summer onset by ~10 days between the 1960s and 2000s. Results from model ensemble simulations dedicated to detection-attribution show that this calendar advance is incompatible with the sole internal climate variability and can be attributed to anthropogenic forcings. Late winter snow disappearance over Eastern Europe affects cold air intrusion to the West when easterlies blow, and is mainly responsible for the observed present-day and near-future summer advance. Our findings agree with phenological-based trends (earlier spring events) reported for many living species over Europe, for which they provide a novel dynamical interpretation beyond the traditionally evoked global warming effect. Based on business-as-usual scenario, a seasonal shift of ~25 days is expected by 2100 for summer onset, while no clear signal arises for winter onset.

Operational forecasting of daily temperatures in the Valencia Region. Part I: maximum temperatures in summer.

Science.gov (United States)

Gómez, I.; Estrela, M.

2009-09-01

Extreme temperature events have a great impact on human society. Knowledge of summer maximum temperatures is very useful for both the general public and organisations whose workers have to operate in the open, e.g. railways, roadways, tourism, etc. Moreover, summer maximum daily temperatures are considered a parameter of interest and concern since persistent heat-waves can affect areas as diverse as public health, energy consumption, etc. Thus, an accurate forecasting of these temperatures could help to predict heat-wave conditions and permit the implementation of strategies aimed at minimizing the negative effects that high temperatures have on human health. The aim of this work is to evaluate the skill of the RAMS model in determining daily maximum temperatures during summer over the Valencia Region. For this, we have used the real-time configuration of this model currently running at the CEAM Foundation. To carry out the model verification process, we have analysed not only the global behaviour of the model for the whole Valencia Region, but also its behaviour for the individual stations distributed within this area. The study has been performed for the summer forecast period of 1 June - 30 September, 2007. The results obtained are encouraging and indicate a good agreement between the observed and simulated maximum temperatures. Moreover, the model captures quite well the temperatures in the extreme heat episodes. Acknowledgement. This work was supported by "GRACCIE" (CSD2007-00067, Programa Consolider-Ingenio 2010), by the Spanish Ministerio de Educación y Ciencia, contract number CGL2005-03386/CLI, and by the Regional Government of Valencia Conselleria de Sanitat, contract "Simulación de las olas de calor e invasiones de frío y su regionalización en la Comunidad Valenciana" ("Heat wave and cold invasion simulation and their regionalization at Valencia Region"). The CEAM Foundation is supported by the Generalitat Valenciana and BANCAIXA (Valencia, Spain).

Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming

KAUST Repository

Sawall, Yvonne

2015-03-10

Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12° latitudes featuring a steep temperature gradient between the northern (28.5°N, 21-27°C) and southern (16.5°N, 28-33°C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29°C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals.

Extensive phenotypic plasticity of a Red Sea coral over a strong latitudinal temperature gradient suggests limited acclimatization potential to warming

KAUST Repository

Sawall, Yvonne; Al-Sofyani, Abdulmoshin; Hohn, Sö nke; Banguera Hinestroza, Eulalia; Voolstra, Christian R.; Wahl, Martin

2015-01-01

Global warming was reported to cause growth reductions in tropical shallow water corals in both, cooler and warmer, regions of the coral species range. This suggests regional adaptation with less heat-tolerant populations in cooler and more thermo-tolerant populations in warmer regions. Here, we investigated seasonal changes in the in situ metabolic performance of the widely distributed hermatypic coral Pocillopora verrucosa along 12° latitudes featuring a steep temperature gradient between the northern (28.5°N, 21-27°C) and southern (16.5°N, 28-33°C) reaches of the Red Sea. Surprisingly, we found little indication for regional adaptation, but strong indications for high phenotypic plasticity: Calcification rates in two seasons (winter, summer) were found to be highest at 28-29°C throughout all populations independent of their geographic location. Mucus release increased with temperature and nutrient supply, both being highest in the south. Genetic characterization of the coral host revealed low inter-regional variation and differences in the Symbiodinium clade composition only at the most northern and most southern region. This suggests variable acclimatization potential to ocean warming of coral populations across the Red Sea: high acclimatization potential in northern populations, but limited ability to cope with ocean warming in southern populations already existing at the upper thermal margin for corals.

Climate change, global warming and coral reefs: modelling the effects of temperature.

Science.gov (United States)

Crabbe, M James C

2008-10-01

Climate change and global warming have severe consequences for the survival of scleractinian (reef-building) corals and their associated ecosystems. This review summarizes recent literature on the influence of temperature on coral growth, coral bleaching, and modelling the effects of high temperature on corals. Satellite-based sea surface temperature (SST) and coral bleaching information available on the internet is an important tool in monitoring and modelling coral responses to temperature. Within the narrow temperature range for coral growth, corals can respond to rate of temperature change as well as to temperature per se. We need to continue to develop models of how non-steady-state processes such as global warming and climate change will affect coral reefs.

The Summer Monsoon of 1987.

Science.gov (United States)

Krishnamurti, T. N.; Bedi, H. S.; Subramaniam, M.

1989-04-01

In this paper we have examined the evolution of a number of parameters we believe were important for our understanding of the drought over India during the summer of 1987. The list of parameters includes monthly means or anomalies of the following fields: sea surface temperatures, divergent circulations, outgoing longwave radiation, streamfunction of the lower and upper troposphere, and monthly precipitation (expressed as a percentage departure from a long-term mean). The El Niño related warm sea surface temperature anomaly and a weaker warm sea surface temperature anomaly over the equatorial Indian Ocean provide sustained convection, as reflected by the negative values of the outgoing longwave radiation. With the seasonal heating, a pronounced planetary-scale divergent circulation evolved with a center along the western Pacific Ocean. The monsoonal divergent circulation merged with that related to the El Niño, maintaining most of the heavy rainfall activity between the equatorial Pacific Ocean and east Asia. Persistent convective activity continued south of India during the entire monsoon season. Strong Hadley type overturnings with rising motions over these warm SST anomaly regions and descent roughly near 20° to 25°S was evident as early as April 1987. The subtropical high pressure areas near 20° to 25°S showed stronger than normal circulations. This was revealed by the presence of a counterclockwise streamfunction anomaly at 850 mb during April 1987. With the seasonal heating, this anomaly moved northwards and was located over the Arabian Sea and India. This countermonsoon circulation anomaly at the low levels was associated with a weaker than normal Somali jet and Arabian Sea circulation throughout this summer. The monsoon remained active along northeast India, Bangladesh, northern lndochina, and central China during the summer monsoon season. This was related to the eastward shift of the divergent circulation. An eastward shift of the upper tropospheric

Warming patterns in regional climate change projections over the Iberian Peninsula

Energy Technology Data Exchange (ETDEWEB)

Gomez-Navarro, J.J.; Montavez, J.P.; Jimenez-Guerrero, P.; Jerez, S. [Murcia Univ. (Spain). Dept. de Fisica; Garcia-Valero, J.A. [Murcia Univ. (Spain). Dept. de Fisica; Delegacion Territorial en Murcia (ES). Agencia Estatal de Meteorologia (AEMET); Gonzalez-Rouco, J.F. [Univ. Complutense, Madrid (Spain). Dept. de Astrofisica y CC. de la Atmosfera

2010-06-15

A set of four regional climate change projections over the Iberian Peninsula has been performed. Simulations were driven by two General Circulation Models (consisting of two versions of the same atmospheric model coupled to two different ocean models) under two different SRES scenario. The XXI century has been simulated following a full-transient approach with a climate version of the mesoscale model MM5. An Empirical Orthogonal Function analysis (EOF) is applied to the monthly mean series of daily maximum and minimum 2-metre temperature to extract the warming signal. The first EOF is able to capture the spatial structure of the warming. The obtained warming patterns are fairly dependent on the month, but hardly change with the tested scenarios and GCM versions. Their shapes are related to geographical parameters, such as distance to the sea and orography. The main differences among simulations mostly concern the temporal evolution of the warming. The temperature trend is stronger for maximum temperatures and depends on the scenario and the driving GCM. This asymmetry, as well as the different warming rates in summer and winter, leads to a continentalization of the climate over the IP. (orig.)

Effects of copper, hypoxia and acute temperature shifts on mitochondrial oxidation in rainbow trout (Oncorhynchus mykiss) acclimated to warm temperature

International Nuclear Information System (INIS)

Sappal, Ravinder; Fast, Mark; Stevens, Don; Kibenge, Fred; Siah, Ahmed; Kamunde, Collins

2015-01-01

Highlights: • Warm acclimation reduced the electron transport system (ETS) efficiency. • Warm acclimation altered the effects of acute temperature shift, hypoxia and Cu on ETS. • Warm acclimation increased thermal sensitivity of state 3 and reduced that of state 4. • Cu stimulated while hypoxia inhibited ETS respiratory activity. • Interactions of Cu and hypoxia on the ETS and plasma metabolites were antagonistic. - Abstract: Temperature fluctuations, hypoxia and metals pollution frequently occur simultaneously or sequentially in aquatic systems and their interactions may confound interpretation of their biological impacts. With a focus on energy homeostasis, the present study examined how warm acclimation influences the responses and interactions of acute temperature shift, hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperature for 3 weeks followed by exposure to environmentally realistic levels of Cu and hypoxia for 24 h. Subsequently, mitochondrial electron transport system (ETS) respiratory activity supported by complexes I–IV (CI–IV), plasma metabolites and condition indices were measured. Warm acclimation reduced fish condition, induced aerobic metabolism and altered the responses of fish to acute temperature shift, hypoxia and Cu. Whereas warm acclimation decelerated the ETS and increased the sensitivity of maximal oxidation rates of the proximal (CI and II) complexes to acute temperature shift, it reduced the thermal sensitivity of state 4 (proton leak). Effects of Cu with and without hypoxia were variable depending on the acclimation status and functional index. Notably, Cu stimulated respiratory activity in the proximal ETS segments, while hypoxia was mostly inhibitory and minimized the stimulatory effect of Cu. The effects of Cu and hypoxia were modified by temperature and showed reciprocal antagonistic interaction on the ETS and plasma

Effects of copper, hypoxia and acute temperature shifts on mitochondrial oxidation in rainbow trout (Oncorhynchus mykiss) acclimated to warm temperature

Energy Technology Data Exchange (ETDEWEB)

Sappal, Ravinder [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Fast, Mark [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Stevens, Don [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Kibenge, Fred [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Siah, Ahmed [British Columbia Centre for Aquatic Health Sciences, 871A Island Highway, Campbell River, British Columbia V9W 2C2 (Canada); Kamunde, Collins, E-mail: ckamunde@upei.ca [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada)

2015-12-15

Highlights: • Warm acclimation reduced the electron transport system (ETS) efficiency. • Warm acclimation altered the effects of acute temperature shift, hypoxia and Cu on ETS. • Warm acclimation increased thermal sensitivity of state 3 and reduced that of state 4. • Cu stimulated while hypoxia inhibited ETS respiratory activity. • Interactions of Cu and hypoxia on the ETS and plasma metabolites were antagonistic. - Abstract: Temperature fluctuations, hypoxia and metals pollution frequently occur simultaneously or sequentially in aquatic systems and their interactions may confound interpretation of their biological impacts. With a focus on energy homeostasis, the present study examined how warm acclimation influences the responses and interactions of acute temperature shift, hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperature for 3 weeks followed by exposure to environmentally realistic levels of Cu and hypoxia for 24 h. Subsequently, mitochondrial electron transport system (ETS) respiratory activity supported by complexes I–IV (CI–IV), plasma metabolites and condition indices were measured. Warm acclimation reduced fish condition, induced aerobic metabolism and altered the responses of fish to acute temperature shift, hypoxia and Cu. Whereas warm acclimation decelerated the ETS and increased the sensitivity of maximal oxidation rates of the proximal (CI and II) complexes to acute temperature shift, it reduced the thermal sensitivity of state 4 (proton leak). Effects of Cu with and without hypoxia were variable depending on the acclimation status and functional index. Notably, Cu stimulated respiratory activity in the proximal ETS segments, while hypoxia was mostly inhibitory and minimized the stimulatory effect of Cu. The effects of Cu and hypoxia were modified by temperature and showed reciprocal antagonistic interaction on the ETS and plasma

Distribution of Polycystine Radiolarians in Bottom Surface Sediments and Its Relation to Summer Sea Temperature in the High-Latitude North Atlantic

Directory of Open Access Journals (Sweden)

Alexander Matul

2017-10-01

Full Text Available An objective of the study is to get new biogeographic information on the modern polycystine radiolarians from the high-latitude North Atlantic. The quantitative radiolarian dataset was compiled from publications and own micropaleontological counts from samples of the bottom surface sediments of the North Atlantic north of 40°N and Nordic Seas. Standard statistical treatment of micropaleontological data by factor analysis reveals five radiolarian assemblages which have their highest load at the specific temperature range in agreement with the oceanographic setting. An occurrence of radiolarian assemblages reflects extension and interaction of the warm North Atlantic and cold Polar/Arctic waters. Radiolarian distribution exhibits good correlation with the climatically averaged summer sea temperature on depth level of 200 m.

Microbial biomass dynamics dominate N cycle responses to warming in a sub-arctic peatland

Science.gov (United States)

Weedon, J. T.; Aerts, R.; Kowalchuk, G. K.; van Bodegom, P. M.

2012-04-01

The balance of primary production and decomposition in sub-arctic peatlands may shift with climate change. Nitrogen availability will modulate this shift, but little is known about the drivers of soil nitrogen dynamics in these environments, and how they are influenced by rising soil temperatures. We used a long-term open top chamber warming experiment in Abisko, Sweden, to test for the interactive effects of spring warming, summer warming and winter snow addition on soil organic and inorganic nitrogen fluxes, potential activities of carbon and nitrogen cycle enzymes, and the structure of the soil-borne microbial communities. Summer warming increased the flux of soil organic nitrogen over the growing season, while simultaneously causing a seasonal decrease in microbial biomass, suggesting that N flux is driven by large late-season dieback of microbes. This change in N cycle dynamics was not reflected in any of the measured potential enzyme activities. Moreover, the soil microbial community structure was stable across treatments, suggesting non-specific microbial dieback. To further test whether the observed patterns were driven by direct temperature effects or indirect effects (via microbial biomass dynamics), we conducted follow-up controlled experiments in soil mesocosms. Experimental additions of dead microbial cells had stronger effects on N pool sizes and enzyme activities than either plant litter addition or a 5 °C alteration in incubation temperatures. Peat respiration was positively affected by both substrate addition and higher incubation temperatures, but the temperature-only effect was not sufficient to account for the increases in respiration observed in previous field experiments. We conclude that warming effects on peatland N cycling (and to some extent C cycling) are dominated by indirect effects, acting through alterations to the seasonal flux of microbe-derived organic matter. We propose that climate change models of soil carbon and nitrogen

Estimating survival rates of quagga mussel (Dreissena rostriformis bugensis veliger larvae under summer and autumn temperature regimes in residual water of trailered watercraft at Lake Mead, USA

Directory of Open Access Journals (Sweden)

Wook Jin Choi

2013-01-01

Full Text Available On 6 January 2007, invasive quagga mussels [Dreissena rostriformis bugensis (Andrusov, 1897] were discovered in the Boulder Basin ofLake Mead, Nevada, a popular site for recreational boating in the southwestern United States. Recreational watercraft are considered aprimary vector for overland dispersal of quagga mussel veliger larvae between water bodies. Thus, effective decontamination of veligers inresidual water carried by trailered recreation boats is critical to controlling this species’ spread. The survival rate of quagga mussel veligerswas measured during exposure to environmental temperature conditions mimicking those experienced in the residual water of traileredvessels during warm summer and cooler autumn months in the semi-arid southwestern United States. Under warm summer conditions,quagga mussel veligers survived approximately five days while under cooler autumn conditions they survived 27 days. When tested underautumn temperature conditions veliger survival times increased with increased level of larval development. The results suggested a greaterlikelihood of veliger transport in the residual water of trailered watercraft during autumn months. The results indicated that presentlyrecommended vessel quarantine times to kill all externally attached juvenile and adult dreissenid mussels prior to launching in an uninfested water body should be increased to generate 100% veliger mortality in residual water unable to be fully drained from the internal areas of watercraft.

Mountain-climbing bears protect cherry species from global warming through vertical seed dispersal.

Science.gov (United States)

Naoe, Shoji; Tayasu, Ichiro; Sakai, Yoichiro; Masaki, Takashi; Kobayashi, Kazuki; Nakajima, Akiko; Sato, Yoshikazu; Yamazaki, Koji; Kiyokawa, Hiroki; Koike, Shinsuke

2016-04-25

In a warming climate, temperature-sensitive plants must move toward colder areas, that is, higher latitude or altitude, by seed dispersal [1]. Considering that the temperature drop with increasing altitude (-0.65°C per 100 m altitude) is one hundred to a thousand times larger than that of the equivalent latitudinal distance [2], vertical seed dispersal is probably a key process for plant escape from warming temperatures. In fact, plant geographical distributions are tracking global warming altitudinally rather than latitudinally, and the extent of tracking is considered to be large in plants with better-dispersed traits (e.g., lighter seeds in wind-dispersed plants) [1]. However, no study has evaluated vertical seed dispersal itself due to technical difficulty or high cost. Here, we show using a stable oxygen isotope that black bears disperse seeds of wild cherry over several hundred meters vertically, and that the dispersal direction is heavily biased towards the mountain tops. Mountain climbing by bears following spring-to-summer plant phenology is likely the cause of this biased seed dispersal. These results suggest that spring- and summer-fruiting plants dispersed by animals may have high potential to escape global warming. Our results also indicate that the direction of vertical seed dispersal can be unexpectedly biased, and highlight the importance of considering seed dispersal direction to understand plant responses to past and future climate change. Copyright © 2016 Elsevier Ltd. All rights reserved.

Summer warming and changes in snow depth is reflected in the growth rings of Alaskan tundra shrubs (Toolik Lake)

Science.gov (United States)

Buchwal, A.; Welker, J. M.

2016-12-01

Arctic change is being manifested by shifts in the vegetation composition and abundance throughout many regions of the Arctic. These changes are primarily reflected by increases in shrub growth and density, but the extent to which shrub growth is expressed in greater shrub ring width and the degree to which natural and experimental warming correspond and or whether the secondary effect of deeper snow in winter acts to alter shrub ring growh and or shrub biomass is yet to be determined for Arctic Alaska. In order to explore growth response of arctic shrubs to on-going and predicted temperature and snow depth increase we investigated shrubs' annual growth rings using dendrochronological methods applied to plants growing under control and experimental treatments in Toolik Lake, Northern Alaska. Specifically we evaluated the effects of a 20-year experimental warming (due to open top chambers, OTC's) and snow depth increases on the growth rings pattern of two common shrub species of Northern Alaska, i.e. Betula nana and Salix pulchra. By applying a serial sectioning method patterns of annual growth were investigated across the entire plant including below-ground parts. Moreover this procedure allowed for a complete cross-dating and a detection of irregular radial growth, including common missing and partially missing rings. We found that the natural warming in Alaska occurring over the past 20 years is stimulating shrub ring growth, more so for Betula than for Salix. Experimental warming (simulating conditions in approximately 2030) stimulated the secondary growth ratio; however the allocation pattern between below-ground and above-ground is quite variable between individual shrubs. In addition, annual growth rings analyses were supplemented by quantitative wood anatomy properties, such as vessel size and density. Our findings indicate that there can be differential growth ring responses of deciduous shrubs to natural climate warming, that growth ring increases reflect

Microclimate impacts of passive warming methods in Antarctica: implications for climate change studies

NARCIS (Netherlands)

Bokhorst, S.; Huiskes, A.H.L.; Convey, P.; Sinclair, B.J.; Lebouvier, M.; van de Vijver, B.; Wall, D.H.

2011-01-01

Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance. In this review, we synthesise and discuss

Effect of global warming on willingness to pay for uninterrupted electricity supply in European nations

Science.gov (United States)

Cohen, Jed; Moeltner, Klaus; Reichl, Johannes; Schmidthaler, Michael

2018-01-01

Predicted changes in temperature and other weather events may damage the electricity grid and cause power outages. Understanding the costs of power outages and how these costs change over time with global warming can inform outage-mitigation-investment decisions. Here we show that across 19 EU nations the value of uninterrupted electricity supply is strongly related to local temperatures, and will increase as the climate warms. Bayesian hierarchical modelling of data from a choice experiment and respondent-specific temperature measures reveals estimates of willingness to pay (WTP) to avoid an hour of power outage between €0.32 and €1.86 per household. WTP varies on the basis of season and is heterogeneous between European nations. Winter outages currently cause larger per household welfare losses than summer outages per hour of outage. However, this dynamic will begin to shift under plausible future climates, with summer outages becoming substantially more costly and winter outages becoming slightly less costly on a per-household, per-hour basis.

Diagnosing the leading mode of interdecadal covariability between the Indian Ocean sea surface temperature and summer precipitation in southern China

Science.gov (United States)

Liu, Jingpeng; Ren, Hong-Li; Li, Weijing; Zuo, Jinqing

2018-03-01

Precipitation in southern China during boreal summer (June to August) shows a substantial interdecadal variability on the timescale longer than 8 years. In this study, based on the analysis of singular value decomposition, we diagnose the leading mode of interdecadal covariability between the observational precipitation in southern China and the sea surface temperature (SST) in the Indian Ocean. Results indicate that there exist a remarkable southern China zonal dipole (SCZD) pattern of interdecadal variability of summer precipitation and an interdecadal Indian Ocean basin mode (ID-IOBM) of SST. It is found that the SCZD is evidently covaried with the ID-IOBM, which may induce anomalous inter-hemispheric vertical circulation and atmospheric Kelvin waves. During the warm phase of the ID-IOBM, an enhanced lower-level convergence and upper-level divergence exist over the tropical Indian Ocean, which is a typical Gill-Matsuno-type response to the SST warming. Meanwhile, the accompanied upper-level outflow anomalies further converge over the Indo-China peninsula, resulting in a lower-level anticyclone that contributes to reduction of the eastward moisture transport from the Bay of Bengal to the west part of southern China. In addition, the Kelvin wave-like pattern, as a response of the warm ID-IOBM phase, further induces the lower-level anticyclonic anomaly over the South China Sea-Philippines. Such an anticyclonic circulation is favorable for more water vapor transport from the East China Sea into the east part of southern China. Therefore, the joint effects of the anomalous inter-hemispheric vertical circulation and the Kelvin wave-like pattern associated with the ID-IOBM may eventually play a key role in generating the SCZD pattern.

The microbial temperature sensitivity to warming is controlled by thermal adaptation and is independent of C-quality across a pan-continental survey

Science.gov (United States)

Berglund, Eva; Rousk, Johannes

2017-04-01

experiments including temperatures from 0 to 35˚ C. Temperature relationships were modelled using the Ratkowsky model, and cardinal points including minimum temperature (Tmin) for growth and respiration along with temperature sensitivity (Q10) values were used as indices to compare sites. Microbial communities were cold-adapted in cold sites and warm-adapted in warm sites, as shown by Tmin values ranging from ca. -20 ˚ C to 0 ˚ C. For every 1˚ C rise in MAT, Tmin increased by 0.22˚ C and 0.28˚ C for bacteria and fungi, respectively. Soil respiration was less dependent on MAT, increasing 0.16 ˚ C per 1˚ C. Temperature dependence analyses grew stronger when regressed against summer temperatures, and weaker when regressed against winter temperatures. Hence, microbial communities adjusted their temperature dependence for growth more than for respiration, and higher temperatures had more impact than low temperatures did. The correlation between Tmin and MAT resulted in Q10s increasing with MAT, showing that microorganisms from cold regions were less temperature sensitive than those from warmer regions. For every 1˚ C increase in MAT, Q10 increased with 0.04 and 0.03 units for bacterial and fungal growth respectively, and 0.08 units for soil respiration. In contrast to previous studies, we found no relationship between temperature sensitivity and substrate quality. We demonstrate that the strongest driver of variation in microbial temperatures sensitivities (Q10s) is the microbial adaptation to its thermal environment. Surprisingly, the quality of SOM had no influence on the temperature sensitivity. This calls for a revision of the understanding for how microbial decomposers feed-back to climate warming. Specifically, the thermal adaptation of microbial communities need to be incorporated into climate models to capture responses to warming, while the quality of SOM can be ignored.

Warm winds from the Pacific caused extensive Arctic sea-ice melt in summer 2007

Energy Technology Data Exchange (ETDEWEB)

Graversen, Rune G.; Drijfhout, Sybren [Royal Netherlands Meteorological Institute, De Bilt (Netherlands); Mauritsen, Thorsten [Max-Planck Institute for Meteorology, Hamburg (Germany); Tjernstroem, Michael; Maartensson, Sebastian [Stockholm University, Department of Meteorology, Stockholm (Sweden)

2011-06-15

During summer 2007 the Arctic sea-ice shrank to the lowest extent ever observed. The role of the atmospheric energy transport in this extreme melt event is explored using the state-of-the-art ERA-Interim reanalysis data. We find that in summer 2007 there was an anomalous atmospheric flow of warm and humid air into the region that suffered severe melt. This anomaly was larger than during any other year in the data (1989-2008). Convergence of the atmospheric energy transport over this area led to positive anomalies of the downward longwave radiation and turbulent fluxes. In the region that experienced unusual ice melt, the net anomaly of the surface fluxes provided enough extra energy to melt roughly one meter of ice during the melting season. When the ocean successively became ice-free, the surface-albedo decreased causing additional absorption of shortwave radiation, despite the fact that the downwelling solar radiation was smaller than average. We argue that the positive anomalies of net downward longwave radiation and turbulent fluxes played a key role in initiating the 2007 extreme ice melt, whereas the shortwave-radiation changes acted as an amplifying feedback mechanism in response to the melt. (orig.)

Effects of recent warm and cold spells on European plant phenology

Science.gov (United States)

Menzel, A.; Estrella, N.; Seifert, H.

2009-04-01

Numerous studies have concurrently documented a progressively earlier start for vegetation activity in spring and a lengthening of the growing season during the last 2 to 5 decades in the temperate northern hemisphere. In contrast to climatic factors influencing autumn phenology, the climate signal controlling spring and summer phenology is fairly well understood: nearly all phenophases correlate with temperatures in the preceding 1 to 3 months. The changes currently experienced by emergence of vegetation may reach 6 to 8 d per °C. But how will this well-known, often linearly described relationship change in case of more frequent and more stronger temperature extremes? We thus studied the temperature response of European phenological records to cold and warm spells using the COST725 data base (www.cost725.org). We restricted our analysis to the time period 1951-2006 due to the relatively better coverage of Europe by phenological records. Up to now, 20 European countries contributed more than 7 Mio. phenological observations to this data base including 64 species and 22 different phases. The phenological observations compiled originated from different sources and phenological networks. Unfortunately there is no entire coverage and the data are very lumped. Cold and warm spells were identified using daily mean temperature data (1951-2006) on a 0.5° grid for Europe provided by the EU-FP6 project ENSEMBLES (http://www.ensembles-eu.org, http://eca.knmi.nl). The study area covered Europe and was limited to 40°E. For the whole study period, mean monthly and seasonal mean temperatures well as the corresponding standard deviations were calculated for each grid point. The annual monthly or seasonal temperature at a grid point was defined as cold (very cold, warm, very warm) by its deviation from the long-term average (more than 1.5 or 3sd, respectively). Warm and cold spells were selected when either the percentages of crossing 1.5sd were greater than 50% for the total

Large Plankton Enhance Heterotrophy Under Experimental Warming in a Temperate Coastal Ecosystem

KAUST Repository

Huete-Stauffer, Tamara Megan

2017-12-15

Microbes are key players in oceanic carbon fluxes. Temperate ecosystems are seasonally variable and thus suitable for testing the effect of warming on microbial carbon fluxes at contrasting oceanographic conditions. In four experiments conducted in February, April, August and October 2013 in coastal NE Atlantic waters, we monitored microbial plankton stocks and daily rates of primary production, bacterial heterotrophic production and respiration at in situ temperature and at 2 and 4°C over ambient values during 4-day incubations. Ambient total primary production (TPP) exceeded total community respiration (< 200 µm, TR) in winter and fall but not in spring and summer. The bacterial contribution to ecosystem carbon fluxes was low, with bacterial production representing on average 6.9 ± 3.2% of TPP and bacterial respiration (between 0.8 and 0.2 µm) contributing on average 35 ± 7% to TR. Warming did not result in a uniform increase in the variables considered, and most significant effects were found only for the 4°C increase. In the summer and fall experiments, under warm and nutrient-deficient conditions, the net TPP/TR ratio decreased by 39 and 34% in the 4°C treatment, mainly due to the increase in respiration of large organisms rather than bacteria. Our results indicate that the interaction of temperature and substrate availability in determining microbial carbon fluxes has a strong seasonal component in temperate planktonic ecosystems, with temperature having a more pronounced effect and generating a shift toward net heterotrophy under more oligotrophic conditions as found in summer and early fall.

Understanding the Asian summer monsoon response to greenhouse warming: the relative roles of direct radiative forcing and sea surface temperature change

Science.gov (United States)

Li, Xiaoqiong; Ting, Mingfang

2017-10-01

Future hydroclimate projections from state-of-the-art climate models show large uncertainty and model spread, particularly in the tropics and over the monsoon regions. The precipitation and circulation responses to rising greenhouse gases involve a fast component associated with direct radiative forcing and a slow component associated with sea surface temperature (SST) warming; the relative importance of the two may contribute to model discrepancies. In this study, regional hydroclimate responses to greenhouse warming are assessed using output from coupled general circulation models in the Coupled Model Intercomparison Project-Phase 5 (CMIP5) and idealized atmospheric general circulation model experiments from the Atmosphere Model Intercomparison Project. The thermodynamic and dynamic mechanisms causing the rainfall changes are examined using moisture budget analysis. Results show that direct radiative forcing and SST change exert significantly different responses both over land and ocean. For most part of the Asian monsoon region, the summertime rainfall changes are dominated by the direct CO2 radiative effect through enhanced monsoon circulation. The response to SST warming shows a larger model spread compared to direct radiative forcing, possibly due to the cancellation between the thermodynamical and dynamical components. While the thermodynamical response of the Asian monsoon is robust across the models, there is a lack of consensus for the dynamical response among the models and weak multi-model mean responses in the CMIP5 ensemble, which may be related to the multiple physical processes evolving on different time scales.

ENSO shifts and their link to Southern Africa surface air temperature in summer

Science.gov (United States)

Manatsa, D.; Mukwada, G.; Makaba, L.

2018-05-01

ENSO has been known to influence the trends of summer warming over Southern Africa. In this work, we used observational and reanalysis data to analyze the relationship between ENSO and maximum surface air temperature (SATmax) trends during the three epochs created by the ENSO phase shifts around 1977 and 1997 for the period 1960 to 2014. We observed that while ENSO and cloud cover remains the dominant factor controlling SATmax variability, the first two epochs had the predominant La Niña (El Niño)-like events connected to robust positive (negative) trends in cloud fraction. However, this established relationship reversed in the post-1997 La Niña-like dominated epoch which coincided with a falling cloud cover trend. It is established that this deviation from the previously established link within the previous epochs could be due to the post-1998 era in which SATmin was suppressed while SATmax was enhanced. The resulting increase in diurnal temperature range (DTR) could have discouraged the formation of low-level clouds which have relatively more extensive areal coverage and hence allowing more solar energy to reach the surface to boost daytime SATmax. It is noted that these relationships are more pronounced from December to March.

Observed Effects of Vegetation Growth on Temperature in the Early Summer over the Northeast China Plain

Directory of Open Access Journals (Sweden)

Xiaxiang Li

2017-05-01

Full Text Available The effect of vegetation on temperature is an emerging topic in the climate science community. Existing studies have mostly examined the effects of vegetation on daytime temperature (Tmax, whereas this study investigates the effects on nighttime temperature (Tmin. Ground measurements from 53 sites across northeastern China (NEC from 1982 to 2006 show that early summer (June Tmax and Tmin increased at mean rates of approximately 0.61 °C/10 year and 0.67 °C/10 year, respectively. Over the same period, the satellite-based Normalized Difference Vegetation Index (NDVI decreased by approximately 0.10 (accounting for 18% of the climatological NDVI for 1982–1991. It is highlighted that a larger increase in Tmax (Tmin co-occurred spatially with a larger (smaller decrease in NDVI. Deriving from such spatial co-occurrences, we found that the spatial variability of changes in Tmax (i.e., ΔTmax is negatively correlated with the spatial variability of changes in NDVI (i.e., ΔNDVI, while the spatial variability of changes in Tmin (i.e., ΔTmin is positively correlated (r2 = 0.10; p < 0.05 with that of ΔNDVI. Similarly, we detected significant positive correlations between the spatial variability of ΔNDVI and the change in surface latent heat flux (r2 = 0.16; p < 0.01 and in surface air specific humidity (r2 = 0.28; p < 0.001. These findings on the spatial co-occurrences suggest that the vegetation growth intensifies the atmospheric water vapor through evapotranspiration, which enhances the atmospheric downward longwave radiation and strengthens the greenhouse warming effects at night. Thereby, the positive correlation between ΔNDVI and ΔTmin is better understood. These results indicate that vegetation growth may not only exert effects on daytime temperature but also exert warming effects on nighttime temperature by increasing atmospheric water vapor and thus intensifying the local greenhouse effect. This study presents new observation evidence of the

In Situ Warming and Soil Venting to Enhance the Biodegradation of JP-4 in Cold Climates: A Critical Study and Analysis

Science.gov (United States)

1995-12-01

1178-1180 (1991). Atlas , Ronald M. and Richard Bartha . Microbial Ecology : Fundamentals and Applications. 3d ed. Redwood City CA: The Benjamin/Cummings...technique called bioventing. In cold climates, in situ bioremediation is limited to the summer when soil temperatures are sufficient to support microbial ...actively warmed the soil -- warm water circulation and heat tape; the other passively warmed the plot with insulatory covers. Microbial respiration (02

Temperature changes in Three Gorges Reservoir Area and linkage with Three Gorges Project

Science.gov (United States)

Song, Zhen; Liang, Shunlin; Feng, Lian; He, Tao; Song, Xiao-Peng; Zhang, Lei

2017-05-01

The Three Gorges Project (TGP) is one of the largest hydroelectric projects throughout the world. It has brought many benefits to the society but also led to endless debates about its environmental and climatic impacts. Monitoring the spatiotemporal variations of temperature in the Three Gorges Reservoir Area (TGRA) is important for understanding the climatic impacts of the TGP. In this study, we used remote sensing-based land surface temperature (LST) and ground-measured air temperature data to investigate temperature changes in the TGRA. Results showed that during the daytime in summer, LST exhibited significant cooling (1-5°C) in the downstream region of the reservoir, whereas LST during the nighttime in winter exhibited significant warming (1-5°C) across the entire reservoir. However, these cooling and warming effects were both locally constrained within 5 km buffer along the reservoir. The changes in air temperature were consistent with those in LST, with 0.67°C cooling in summer and 0.33°C warming in winter. The temperature changes along the reservoir not only resulted from the land-water conversion induced by the dam impounding but were also related to the increase of vegetation cover caused by the ecological restoration projects. Significant warming trends were also found in the upstream of TGRA, especially during the daytime in summer, with up to 5°C for LST and 0.52°C for air temperature. The warming was caused mainly by urban expansion, which was driven in part by the population resettlement of TGP. Based on satellite observations, we investigated the comprehensive climatic impacts of TGP caused by multiple factors.

Reduced connection between the East Asian Summer Monsoon and Southern Hemisphere Circulation on interannual timescales under intense global warming

Science.gov (United States)

Yu, Tianlei; Guo, Pinwen; Cheng, Jun; Hu, Aixue; Lin, Pengfei; Yu, Yongqiang

2018-03-01

Previous studies show a close relationship between the East Asian Summer Monsoon (EASM) and Southern Hemisphere (SH) circulation on interannual timescales. In this study, we investigate whether this close relationship will change under intensive greenhouse-gas effect by analyzing simulations under two different climate background states: preindustrial era and Representative Concentration Pathway (RCP) 8.5 stabilization from the Community Climate System Model Version 4 (CCSM4). Results show a significantly reduced relationship under stabilized RCP8.5 climate state, such a less correlated EASM with the sea level pressure in the southern Indian Ocean and the SH branch of local Hadley Cell. Further analysis suggests that the collapse of the Atlantic Meridional Overturning Circulation (AMOC) due to this warming leads to a less vigorous northward meridional heat transport, a decreased intertropical temperature contrast in boreal summer, which produces a weaker cross-equatorial Hadley Cell in the monsoonal region and a reduced Interhemispheric Mass Exchange (IME). Since the monsoonal IME acts as a bridge connecting EASM and SH circulation, the reduced IME weakens this connection. By performing freshwater hosing experiment using the Flexible Global Ocean—Atmosphere—Land System model, Grid-point Version 2 (FGOALS-g2), we show a weakened relationship between the EASM and SH circulation as in CCSM4 when AMOC collapses. Our results suggest that a substantially weakened AMOC is the main driver leading to the EASM, which is less affected by SH circulation in the future warmer climate.

Effects of air temperature and discharge on Upper Mississippi River summer water temperatures

Science.gov (United States)

Gray, Brian R.; Robertson, Dale M.; Rogala, James T.

2018-01-01

Recent interest in the potential effects of climate change has prompted studies of air temperature and precipitation associations with water temperatures in rivers and streams. We examined associations between summer surface water temperatures and both air temperature and discharge for 5 reaches of the Upper Mississippi River during 1994–2011. Water–air temperature associations at a given reach approximated 1:1 when estimated under an assumption of reach independence but declined to approximately 1:2 when water temperatures were permitted to covary among reaches and were also adjusted for upstream air temperatures. Estimated water temperature–discharge associations were weak. An apparently novel feature of this study is that of addressing changes in associations between water and air temperatures when both are correlated among reaches.

A phenological timetable of oak growth under experimental drought and air warming.

Directory of Open Access Journals (Sweden)

Thomas M Kuster

Full Text Available Climate change is expected to increase temperature and decrease summer precipitation in Central Europe. Little is known about how warming and drought will affect phenological patterns of oaks, which are considered to possess excellent adaptability to these climatic changes. Here, we investigated bud burst and intra-annual shoot growth of Quercus robur, Q. petraea and Q. pubescens grown on two different forest soils and exposed to air warming and drought. Phenological development was assessed over the course of three growing seasons. Warming advanced bud burst by 1-3 days °C⁻¹ and led to an earlier start of intra-annual shoot growth. Despite this phenological shift, total time span of annual growth and shoot biomass were not affected. Drought changed the frequency and intensity of intra-annual shoot growth and advanced bud burst in the subsequent spring of a severe summer drought by 1-2 days. After re-wetting, shoot growth recovered within a few days, demonstrating the superior drought tolerance of this tree genus. Our findings show that phenological patterns of oaks are modified by warming and drought but also suggest that ontogenetic factors and/or limitations of water and nutrients counteract warming effects on the biomass and the entire span of annual shoot growth.

Global warming in the context of 2000 years of Australian alpine temperature and snow cover.

Science.gov (United States)

McGowan, Hamish; Callow, John Nikolaus; Soderholm, Joshua; McGrath, Gavan; Campbell, Micheline; Zhao, Jian-Xin

2018-03-13

Annual resolution reconstructions of alpine temperatures are rare, particularly for the Southern Hemisphere, while no snow cover reconstructions exist. These records are essential to place in context the impact of anthropogenic global warming against historical major natural climate events such as the Roman Warm Period (RWP), Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Here we show for a marginal alpine region of Australia using a carbon isotope speleothem reconstruction, warming over the past five decades has experienced equivalent magnitude of temperature change and snow cover decline to the RWP and MCA. The current rate of warming is unmatched for the past 2000 years and seasonal snow cover is at a minimum. On scales of several decades, mean maximum temperatures have undergone considerable change ≈ ± 0.8 °C highlighting local scale susceptibility to rapid temperature change, evidence of which is often masked in regional to hemisphere scale temperature reconstructions.

Soil Temperature Manipulation to Study Global Warming Effects in Arable Land

DEFF Research Database (Denmark)

Patil, R H; Laegdsmand, M; Olesen, Jørgen E

2013-01-01

in a plough layer. Temperature sensors were placed at 0.05, 0.1 and 0.25 m depths in soil, and 0.1 m above the soil surface in all plots, which were connected to an automated data logger. Soil-warming setup was able to maintain a mean seasonal temperature difference of 5.0 ± 0.005℃ between heated and control......-ground vegetation response as this method heats only the soil. Therefore, using infrared heaters seems to represent natural climate warming (both air and soil) much more closely and may be used for future climate manipulation field studies....

Soil temperature manipulation to study global warming effects in arable land

DEFF Research Database (Denmark)

Patil, Raveendra H.; Laegdsmand, Mette; Olesen, Jørgen Eivind

2013-01-01

in a plough layer. Temperature sensors were placed at 0.05, 0.1 and 0.25 m depths in soil, and 0.1 m above the soil surface in all plots, which were connected to an automated data logger. Soil-warming setup was able to maintain a mean seasonal temperature difference of 5.0 ± 0.005 oC between heated...... that of above-ground vegetation response as this method heats only the soil. Therefore, using infrared heaters seems to represent natural climate warming (both air and soil) much more closely and may be used for future climate manipulation field studies....

Plot-scale evidence of tundra vegetation change and links to recent summer warming

Science.gov (United States)

Sarah C. Elmendorf; Gregory H.R. Henry; Robert D. Hollister; Robert G. Bjork; Noemie Boulanger-Lapointe; Elisabeth J. Cooper; Johannes H.C. Cornelissen; Thomas A. Day; Ellen Dorrepaal; Tatiana G. Elumeeva; Mike Gill; William A. Gould; John Harte; David S. Hik; Annika Hofgaard; David R. Johnson; Jill F. Johnstone; Ingijorg Svala Jonsdottir; Janet C. Jorgenson; Kari Klanderud; Julia A. Klein; Saewan Koh; Gaku Kudo; Mark Lara; Esther Levesque; Borgthor Magnusson; Jeremy L. May; Joel A. Mercado; Anders Michelsen; Ulf Molau; Isla H. Myers-Smith; Steven F. Oberbauer; Vladimir G. Onipchenko; Christian Rixen; Niels Martin Schmidt; Gaius R. Shaver; Marko J. Spasojevic; Pora Ellen Porhallsdottir; Anne Tolvanen; Tiffany Troxler; Craig E. Tweedie; Sandra Villareal; Carl-Henrik Wahren; Xanthe Walker; Patrick J. Webber; Jeffrey M. Welker; Sonja Wipf

2012-01-01

Temperature is increasing at unprecedented rates across most of the tundra biome1. Remote-sensing data indicate that contemporary climate warming has already resulted in increased productivity over much of the Arctic2,3, but plot-based evidence for vegetation transformation is not widespread. We analysed change in tundra vegetation surveyed between 1980 and 2010 in 158...

Phylogeographic differentiation versus transcriptomic adaptation to warm temperatures in Zostera marina, a globally important seagrass

NARCIS (Netherlands)

Jueterbock, Alexander; Franssen, S. U.; Bergmann, N.; Gu, J.; Coyer, J. A.; Reusch, T. B. H.; Bornberg-Bauer, E.; Olsen, J. L.

2016-01-01

Populations distributed across a broad thermal cline are instrumental in addressing adaptation to increasing temperatures under global warming. Using a space-for-time substitution design, we tested for parallel adaptation to warm temperatures along two independent thermal clines in Zostera marina,

Trends and changes in tropical and summer days at the Adana Sub-Region of the Mediterranean Region, Southern Turkey

Science.gov (United States)

Bayer Altın, Türkan; Barak, Belma

2017-11-01

In this study, the long-term variability and trends of the annual and seasonal numbers of summer and tropical days of the Adana Sub-region were investigated using nonlinear and linear trend detection tests for the period 1960-2014 at 14 meteorological stations. The results suggest that the annual number of summer and tropical days was generally below the long-term average through to the end of the 1980s. In particular, positive anomaly values could be observed at all stations between the years 1993-2014. With respect to the Kruskal-Wallis homogeneity test, the significant breaking date was 1993. The rapid rise of the annual number of summer (tropical) days after this year led to the inversion of the negative trends observed from 1987 to 1992 into positive ones. The increasing trend is statistically significance at 0.01 level in Yumurtalık, Mersin and Antakya for the annual number of summer and tropical days. Dörtyol, İskenderun and Elbistan were significance at 0.01 level for tropical days. The largest positive anomalies of the summer of 2010 are observed in coastal vicinity (Mersin, Yumurtalık and İskenderun). This indicates that these settlements underwent a long-term warm period and thermal conditions due to increasing temperatures in the spring and summer months. The same conditions are found in high inner areas (Göksun and Elbistan) for tropical days. It is noticed that a tendency for greater warming occurred at stations located above 1000 m in the sub-region. The average number of warm days will increase 2-days per 100-years in southern part of the sub-region. The increasing trend in summer temperatures can be considered a potential risk, notably for human health and for economic and crop losses in the Adana Sub-region, including Çukurova, one of the most important agriculture areas of Turkey.

Upper lethal temperatures in three cold-tolerant insects are higher in winter than in summer.

Science.gov (United States)

Vu, Henry M; Duman, John G

2017-08-01

Upper lethal temperatures (ULTs) of cold-adapted insect species in winter have not been previously examined. We anticipated that as the lower lethal temperatures (LLTs) decreased (by 20-30°C) with the onset of winter, the ULTs would also decrease accordingly. Consequently, given the recent increases in winter freeze-thaw cycles and warmer winters due to climate change, it became of interest to determine whether ambient temperatures during thaws were approaching ULTs during the cold seasons. However, beetle Dendroides canadensis (Coleoptera: Pyrochroidae) larvae had higher 24 and 48 h ULT 50 (the temperature at which 50% mortality occurred) in winter than in summer. The 24 and 48 h ULT 50 for D. canadensis in winter were 40.9 and 38.7°C, respectively. For D. canadensis in summer, the 24 and 48 h ULT 50 were 36.7 and 36.4°C. During the transition periods of spring and autumn, the 24 h ULT 50 was 37.3 and 38.5°C, respectively. While D. canadensis in winter had a 24 h LT 50 range between LLT and ULT of 64°C, the summer range was only 41°C. Additionally, larvae of the beetle Cucujus clavipes clavipes (Coleoptera: Cucujidae) and the cranefly Tipula trivittata (Diptera: Tipulidae) also had higher ULTs in winter than in summer. This unexpected phenomenon of increased temperature survivorship at both lower and higher temperatures in the winter compared with that in the summer has not been previously documented. With the decreased high temperature tolerance as the season progresses from winter to summer, it was observed that environmental temperatures are closest to upper lethal temperatures in spring. © 2017. Published by The Company of Biologists Ltd.

Non-linear trends and fluctuations in temperature during different growth stages of summer maize in the North China Plain from 1960 to 2014

Science.gov (United States)

Wang, Cailin; Wu, Jidong; Wang, Xu; He, Xin; Li, Ning

2017-12-01

North China Plain has undergone severe warming trends since the 1950s, but whether this trend is the same during different growth phases for crops remains unknown. Thus, we analyzed the non-linear changes in the minimum temperature (T min ), mean temperature (T mean ) and maximum temperature (T max ) using the Ensemble Empirical Mode Decomposition method during each growth stage of summer maize based on daily temperature data from 1960 to 2014. Our results strongly suggest that the trends and fluctuations in temperature change are non-linear. These changes can be categorized into four types of trend change according to the combinations of decreasing and increasing trends, and 8 fluctuation modes dominated by the fluctuations of expansion and shrinkage. The amplitude of the fluctuation is primarily expansion in the sowing-jointing stage and shrinkage in the jointing-maturity stage. Moreover, the temperature changes are inconsistent within each growth stage and are not consistent with the overall warming trend observed over the last 55 years. A transition period occurred in both the 1980s and the 1990s for temperatures during the sowing-tasseling stage. Furthermore, the cooling trend of the T max was significant in the sowing-emergence stage, while this cooling trend was not obvious for both T mean and T min in the jointing-tasseling stage. These results showed that temperature change was significantly different in different stages of the maize growth season. The results can serve as a scientific basis for a better understanding of the actual changes in the regional surface air temperature and agronomic heat resources.

EXTREME MAXIMUM AND MINIMUM AIR TEMPERATURE IN MEDİTERRANEAN COASTS IN TURKEY

Directory of Open Access Journals (Sweden)

Barbaros Gönençgil

2016-01-01

Full Text Available In this study, we determined extreme maximum and minimum temperatures in both summer and winter seasons at the stations in the Mediterranean coastal areas of Turkey.In the study, the data of 24 meteorological stations for the daily maximum and minimumtemperatures of the period from 1970–2010 were used. From this database, a set of four extreme temperature indices applied warm (TX90 and cold (TN10 days and warm spells (WSDI and cold spell duration (CSDI. The threshold values were calculated for each station to determine the temperatures that were above and below the seasonal norms in winter and summer. The TX90 index displays a positive statistically significant trend, while TN10 display negative nonsignificant trend. The occurrence of warm spells shows statistically significant increasing trend while the cold spells shows significantly decreasing trend over the Mediterranean coastline in Turkey.

The upper end of climate model temperature projections is inconsistent with past warming

International Nuclear Information System (INIS)

Stott, Peter; Good, Peter; Jones, Gareth; Gillett, Nathan; Hawkins, Ed

2013-01-01

Climate models predict a large range of possible future temperatures for a particular scenario of future emissions of greenhouse gases and other anthropogenic forcings of climate. Given that further warming in coming decades could threaten increasing risks of climatic disruption, it is important to determine whether model projections are consistent with temperature changes already observed. This can be achieved by quantifying the extent to which increases in well mixed greenhouse gases and changes in other anthropogenic and natural forcings have already altered temperature patterns around the globe. Here, for the first time, we combine multiple climate models into a single synthesized estimate of future warming rates consistent with past temperature changes. We show that the observed evolution of near-surface temperatures appears to indicate lower ranges (5–95%) for warming (0.35–0.82 K and 0.45–0.93 K by the 2020s (2020–9) relative to 1986–2005 under the RCP4.5 and 8.5 scenarios respectively) than the equivalent ranges projected by the CMIP5 climate models (0.48–1.00 K and 0.51–1.16 K respectively). Our results indicate that for each RCP the upper end of the range of CMIP5 climate model projections is inconsistent with past warming. (letter)

Irrigation offsets wheat yield reductions from warming temperatures

Science.gov (United States)

Tack, Jesse; Barkley, Andrew; Hendricks, Nathan

2017-11-01

Temperature increases due to climate change are expected to cause substantial reductions in global wheat yields. However, uncertainty remains regarding the potential role for irrigation as an adaptation strategy to offset heat impacts. Here we utilize over 7000 observations spanning eleven Kansas field-trial locations, 180 varieties, and 29 years to show that irrigation significantly reduces the negative impact of warming temperatures on winter wheat yields. Dryland wheat yields are estimated to decrease about eight percent for every one-degree Celsius increase in temperature, yet irrigation completely offsets this negative impact in our sample. As in previous studies, we find that important interactions exist between heat stress and precipitation for dryland production. Here, uniquely, we observe both dryland and irrigated trials side-by-side at the same locations and find that precipitation does not provide the same reduction in heat stress as irrigation. This is likely to be because the timing, intensity, and volume of water applications influence wheat yields, so the ability to irrigate—rather than relying on rainfall alone—has a stronger influence on heat stress. We find evidence of extensive differences of water-deficit stress impacts across varieties. This provides some evidence of the potential for adapting to hotter and drier climate conditions using optimal variety selection. Overall, our results highlight the critical role of water management for future global food security. Water scarcity not only reduces crop yields through water-deficit stress, but also amplifies the negative effects of warming temperatures.

Unusually Warm Spring Temperatures Magnify Annual CH4 Losses From Arctic Ecosystems

Science.gov (United States)

Goodrich, J. P.; Oechel, W. C.; Gioli, B.; Murphy, P.; Zona, D.

2015-12-01

The relatively fast pace of Northern high latitude warming puts the very large permafrost soil C pool at a higher risk of being lost to the atmosphere as CH4. Estimates for the Arctic tundra's contribution to the global wetland CH4 emissions range from 15-27 TgCH4 y-1 (8-14% of total). However, these estimates are largely based on data from the growing season, or from boreal systems underlain by discontinuous permafrost with different physical, hydrological, and biogeochemical dynamics than continuous permafrost zones. Recent data from a transect of eddy covariance flux towers across the North Slope of Alaska revealed the importance of cold season emissions to the annual CH4 budget, which may not correlate with summer flux patterns. However, understanding of the controls and inter-annual variability in fluxes at these different sites is lacking. Here, we present data from ~3 years at 5 tundra ecosystems along this Arctic transect to show the influence of earlier and deeper spring active layer thaw on timing and magnitude of CH4 fluxes. This year's warm spring led to significantly greater thaw depths and lower water tables than the previous year. Substantial CH4 emissions in 2015 were recorded at the wettest sites >20 days earlier than in the more meteorologically normal previous year. Since the soil remained saturated despite a lowered water table, total spring CH4 emissions more than doubled at these wet sites. At the drier sites, soil moisture declined with water table during the warmer spring, resulting in similar emissions to the previous year. However, deeper thaw depths prolonged fall and early winter emissions during the 'zero-curtain' soil temperature freezing phase, particularly at the drier site. In general, warmer spring temperatures in the Arctic may result in large increases in early season CH4 losses at wet sites and prolonged steady losses at the upland sites, enhancing the feedback between changing climate and tundra CH4 emissions at all sites.

Summer outdoor temperature and occupational heat-related illnesses in Quebec (Canada)

International Nuclear Information System (INIS)

Adam-Poupart, Ariane; Smargiassi, Audrey; Busque, Marc-Antoine; Duguay, Patrice; Fournier, Michel; Zayed, Joseph; Labrèche, France

2014-01-01

Background: Predicted rise in global mean temperature and intensification of heat waves associated with climate change present an increasing challenge for occupational health and safety. Although important scientific knowledge has been gathered on the health effects of heat, very few studies have focused on quantifying the association between outdoor heat and mortality or morbidity among workers. Objective: To quantify the association between occupational heat-related illnesses and exposure to summer outdoor temperatures. Methods: We modeled 259 heat-related illnesses compensated by the Workers' Compensation Board of Quebec between May and September, from 1998 to 2010, with maximum daily summer outdoor temperatures in 16 health regions of Quebec (Canada) using generalized linear models with negative binomial distributions, and estimated the pooled effect sizes for all regions combined, by sex and age groups, and for different time lags with random-effect models for meta-analyses. Results: The mean daily compensation count was 0.13 for all regions of Quebec combined. The relationship between daily counts of compensations and maximum daily temperatures was log-linear; the pooled incidence rate ratio (IRR) of daily heat-related compensations per 1 °C increase in daily maximum temperatures was 1.419 (95% CI 1.326 to 1.520). Associations were similar for men and women and by age groups. Increases in daily maximum temperatures at lags 1 and 2 and for two and three-day lag averages were also associated with increases in daily counts of compensations (IRRs of 1.206 to 1.471 for every 1 °C increase in temperature). Conclusion: This study is the first to quantify the association between occupational heat-related illnesses and exposure to summer temperatures in Canada. The model (risk function) developed in this study could be useful to improve the assessment of future impacts of predicted summer outdoor temperatures on workers and vulnerable groups, particularly in

Summer outdoor temperature and occupational heat-related illnesses in Quebec (Canada)

Energy Technology Data Exchange (ETDEWEB)

Adam-Poupart, Ariane [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Smargiassi, Audrey [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Institut national de santé publique du Québec (INSPQ), Montreal, QC (Canada); Busque, Marc-Antoine; Duguay, Patrice [Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montreal, QC (Canada); Fournier, Michel [Direction de santé publique, Agence de la santé et des services sociaux de Montréal, Montreal, QC (Canada); Zayed, Joseph [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montreal, QC (Canada); Labrèche, France, E-mail: labreche.france@irsst.qc.ca [Department of Environmental and Occupational Health, School of Public Health, Université de Montréal, Montreal, QC (Canada); Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montreal, QC (Canada)

2014-10-15

Background: Predicted rise in global mean temperature and intensification of heat waves associated with climate change present an increasing challenge for occupational health and safety. Although important scientific knowledge has been gathered on the health effects of heat, very few studies have focused on quantifying the association between outdoor heat and mortality or morbidity among workers. Objective: To quantify the association between occupational heat-related illnesses and exposure to summer outdoor temperatures. Methods: We modeled 259 heat-related illnesses compensated by the Workers' Compensation Board of Quebec between May and September, from 1998 to 2010, with maximum daily summer outdoor temperatures in 16 health regions of Quebec (Canada) using generalized linear models with negative binomial distributions, and estimated the pooled effect sizes for all regions combined, by sex and age groups, and for different time lags with random-effect models for meta-analyses. Results: The mean daily compensation count was 0.13 for all regions of Quebec combined. The relationship between daily counts of compensations and maximum daily temperatures was log-linear; the pooled incidence rate ratio (IRR) of daily heat-related compensations per 1 °C increase in daily maximum temperatures was 1.419 (95% CI 1.326 to 1.520). Associations were similar for men and women and by age groups. Increases in daily maximum temperatures at lags 1 and 2 and for two and three-day lag averages were also associated with increases in daily counts of compensations (IRRs of 1.206 to 1.471 for every 1 °C increase in temperature). Conclusion: This study is the first to quantify the association between occupational heat-related illnesses and exposure to summer temperatures in Canada. The model (risk function) developed in this study could be useful to improve the assessment of future impacts of predicted summer outdoor temperatures on workers and vulnerable groups, particularly in

Early onset of significant local warming in low latitude countries

International Nuclear Information System (INIS)

Mahlstein, I; Knutti, R; Solomon, S; Portmann, R W

2011-01-01

The Earth is warming on average, and most of the global warming of the past half-century can very likely be attributed to human influence. But the climate in particular locations is much more variable, raising the question of where and when local changes could become perceptible enough to be obvious to people in the form of local warming that exceeds interannual variability; indeed only a few studies have addressed the significance of local signals relative to variability. It is well known that the largest total warming is expected to occur in high latitudes, but high latitudes are also subject to the largest variability, delaying the emergence of significant changes there. Here we show that due to the small temperature variability from one year to another, the earliest emergence of significant warming occurs in the summer season in low latitude countries (∼25 deg. S-25 deg. N). We also show that a local warming signal that exceeds past variability is emerging at present, or will likely emerge in the next two decades, in many tropical countries. Further, for most countries worldwide, a mean global warming of 1 deg. C is sufficient for a significant temperature change, which is less than the total warming projected for any economically plausible emission scenario. The most strongly affected countries emit small amounts of CO 2 per capita and have therefore contributed little to the changes in climate that they are beginning to experience.

Tensile deformation behavior of AA5083-H111 at cold and warm temperatures

Energy Technology Data Exchange (ETDEWEB)

Ozturk, Fahrettin; Toros, Serkan; Kilic, Suleyman [Nidge Univ. (Turkey). Dept. of Mechanical Engineering

2010-09-15

The effects of strain rate and temperature on the deformation behavior of hardened 5083-H111 aluminum magnesium alloy sheet were investigated by performing uniaxial tensile tests at various strain rates from 0.0083 to 0.16 s{sup -1} and temperatures from -100 to 300 C. Results from the prescribed test ranges indicate that the formability of this material at cold and warm temperatures is better than at room temperature. The improvement in formability at cold temperatures is principally due to the strain hardening of the material. However, the improvement at warm temperature and low strain rate is specifically due to the high strain rate sensitivity characteristic of the material. Results indicate that this alloy should be formed at temperatures higher than 200 C and at low strain rates. (orig.)

Increased air temperature during simulated autumn conditions does not increase photosynthetic carbon gain but affects the dissipation of excess energy in seedlings of the evergreen conifer Jack pine.

Science.gov (United States)

Busch, Florian; Hüner, Norman P A; Ensminger, Ingo

2007-03-01

Temperature and daylength act as environmental signals that determine the length of the growing season in boreal evergreen conifers. Climate change might affect the seasonal development of these trees, as they will experience naturally decreasing daylength during autumn, while at the same time warmer air temperature will maintain photosynthesis and respiration. We characterized the down-regulation of photosynthetic gas exchange and the mechanisms involved in the dissipation of energy in Jack pine (Pinus banksiana) in controlled environments during a simulated summer-autumn transition under natural conditions and conditions with altered air temperature and photoperiod. Using a factorial design, we dissected the effects of daylength and temperature. Control plants were grown at either warm summer conditions with 16-h photoperiod and 22 degrees C or conditions representing a cool autumn with 8 h/7 degrees C. To assess the impact of photoperiod and temperature on photosynthesis and energy dissipation, plants were also grown under either cold summer (16-h photoperiod/7 degrees C) or warm autumn conditions (8-h photoperiod/22 degrees C). Photosynthetic gas exchange was affected by both daylength and temperature. Assimilation and respiration rates under warm autumn conditions were only about one-half of the summer values but were similar to values obtained for cold summer and natural autumn treatments. In contrast, photosynthetic efficiency was largely determined by temperature but not by daylength. Plants of different treatments followed different strategies for dissipating excess energy. Whereas in the warm summer treatment safe dissipation of excess energy was facilitated via zeaxanthin, in all other treatments dissipation of excess energy was facilitated predominantly via increased aggregation of the light-harvesting complex of photosystem II. These differences were accompanied by a lower deepoxidation state and larger amounts of beta-carotene in the warm autumn

Coupling in the middle atmosphere related to the 2013 major sudden stratospheric warming

Directory of Open Access Journals (Sweden)

R. J. de Wit

2015-03-01

Full Text Available The previously reported observation of anomalous eastward gravity wave forcing at mesopause heights around the onset of the January 2013 major sudden stratospheric warming (SSW over Trondheim, Norway (63° N, 10° E, is placed in a global perspective using Microwave Limb Sounder (MLS temperature observations from the Aura satellite. It is shown that this anomalous forcing results in a clear cooling over Trondheim about 10 km below mesopause heights. Conversely, near the mesopause itself, where the gravity wave forcing was measured, observations with meteor radar, OH airglow and MLS show no distinct cooling. Polar cap zonal mean temperatures show a similar vertical profile. Longitudinal variability in the high northern-latitude mesosphere and lower thermosphere (MLT is characterized by a quasi-stationary wave-1 structure, which reverses phase at altitudes below ~ 0.1 hPa. This wave-1 develops prior to the SSW onset, and starts to propagate westward at the SSW onset. The latitudinal pole-to-pole temperature structure associated with the major SSW shows a warming (cooling in the winter stratosphere (mesosphere which extends to about 40° N. In the stratosphere, a cooling extending over the equator and far into the summer hemisphere is observed, whereas in the mesosphere an equatorial warming is noted. In the Southern Hemisphere mesosphere, a warm anomaly overlaying a cold anomaly is present, which is shown to propagate downward in time. This observed structure is in accordance with the temperature perturbations predicted by the proposed interhemispheric coupling mechanism for cases of increased winter stratospheric planetary wave activity, of which major SSWs are an extreme case. These results provide observational evidence for the interhemispheric coupling mechanism, and for the wave-mean flow interaction believed to be responsible for the establishment of the anomalies in the summer hemisphere.

Upper temperature limits of tropical marine ectotherms: global warming implications.

Directory of Open Access Journals (Sweden)

Khanh Dung T Nguyen

Full Text Available Animal physiology, ecology and evolution are affected by temperature and it is expected that community structure will be strongly influenced by global warming. This is particularly relevant in the tropics, where organisms are already living close to their upper temperature limits and hence are highly vulnerable to rising temperature. Here we present data on upper temperature limits of 34 tropical marine ectotherm species from seven phyla living in intertidal and subtidal habitats. Short term thermal tolerances and vertical distributions were correlated, i.e., upper shore animals have higher thermal tolerance than lower shore and subtidal animals; however, animals, despite their respective tidal height, were susceptible to the same temperature in the long term. When temperatures were raised by 1°C hour(-1, the upper lethal temperature range of intertidal ectotherms was 41-52°C, but this range was narrower and reduced to 37-41°C in subtidal animals. The rate of temperature change, however, affected intertidal and subtidal animals differently. In chronic heating experiments when temperature was raised weekly or monthly instead of every hour, upper temperature limits of subtidal species decreased from 40°C to 35.4°C, while the decrease was more than 10°C in high shore organisms. Hence in the long term, activity and survival of tropical marine organisms could be compromised just 2-3°C above present seawater temperatures. Differences between animals from environments that experience different levels of temperature variability suggest that the physiological mechanisms underlying thermal sensitivity may vary at different rates of warming.

European temperature responses to blocking and ridge regional patterns

Science.gov (United States)

Sousa, Pedro M.; Trigo, Ricardo M.; Barriopedro, David; Soares, Pedro M. M.; Santos, João A.

2018-01-01

Blocking occurrence and its impacts on European temperature have been studied in the last decade. However, most previous studies on blocking impacts have focused on winter only, disregarding its fingerprint in summer and differences with other synoptic patterns that also trigger temperature extremes. In this work, we provide a clear distinction between high-latitude blocking and sub-tropical ridges occurring in three sectors of the Euro-Atlantic region, describing their climatology and consequent impacts on European temperature during both winter and summer. Winter blocks (ridges) are generally associated to colder (warmer) than average conditions over large regions of Europe, in some areas with anomalies larger than 5 °C, particularly for the patterns occurring in the Atlantic and Central European sectors. During summer, there is a more regional response characterized by above average temperature for both blocking and ridge patterns, especially those occurring in continental areas, although negative temperature anomalies persist in southernmost areas during blocking. An objective analysis of the different forcing mechanisms associated to each considered weather regime has been performed, quantifying the importance of the following processes in causing the temperature anomalies: horizontal advection, vertical advection and diabatic heating. While during winter advection processes tend to be more relevant to explain temperature responses, in summer radiative heating under enhanced insolation plays a crucial role for both blocking and ridges. Finally, the changes in the distributions of seasonal temperature and in the frequencies of extreme temperature indices were also examined for specific areas of Europe. Winter blocking and ridge patterns are key drivers in the occurrence of regional cold and warm extreme temperatures, respectively. In summer, they are associated with substantial changes in the frequency of extremely warm days, but with different signatures in

Climate change affects low trophic level marine consumers: warming decreases copepod size and abundance.

Science.gov (United States)

Garzke, Jessica; Ismar, Stefanie M H; Sommer, Ulrich

2015-03-01

Concern about climate change has re-ignited interest in universal ecological responses to temperature variations: (1) biogeographical shifts, (2) phenology changes, and (3) size shifts. In this study we used copepods as model organisms to study size responses to temperature because of their central role in the pelagic food web and because of the ontogenetic length constancy between molts, which facilitates the definition of size of distinct developmental stages. In order to test the expected temperature-induced shifts towards smaller body size and lower abundances under warming conditions, a mesocosm experiment using plankton from the Baltic Sea at three temperature levels (ambient, ambient +4 °C, ambient -4 °C) was performed in summer 2010. Overall copepod and copepodit abundances, copepod size at all life stages, and adult copepod size in particular, showed significant temperature effects. As expected, zooplankton peak abundance was lower in warm than in ambient treatments. Copepod size-at-immature stage significantly increased in cold treatments, while adult size significantly decreased in warm treatments.

Arctic plants are capable of sustained responses to long-term warming

Directory of Open Access Journals (Sweden)

Robert T. Barrett

2016-05-01

Full Text Available Previous studies have shown that Arctic plants typically respond to warming with increased growth and reproductive effort and accelerated phenology, and that the magnitude of these responses is likely to change over time. We investigated the effects of long-term experimental warming on plant growth (leaf length and reproduction (inflorescence height, reproductive phenology and reproductive effort using 17–19 years of measurements collected as part of the International Tundra Experiment (ITEX at sites near Barrow and Atqasuk, Alaska. During the study period, linear regressions indicated non-significant tendencies towards warming air temperatures at our study sites. Results of our meta-analyses on the effect size of experimental warming (calculated as Hedges’ d indicated species generally responded to warming by increasing inflorescence height, increasing leaf length and flowering earlier, while reproductive effort did not respond consistently. Using weighted least-squares regressions on effect sizes, we found a significant trend towards dampened response to experimental warming over time for reproductive phenology. This tendency was consistent, though non-significant, across all traits. A separate analysis revealed significant trends towards reduced responses to experimental warming during warmer summers for all traits. We therefore propose that tendencies towards dampened plant responses to experimental warming over time are the result of regional warming. These results show that Arctic plants are capable of sustained responses to warming over long periods of time but also suggest that, as the region continues to warm, factors such as nutrient availability, competition and herbivory will become more limiting to plant growth and reproduction than temperature.

First results of warm mesospheric temperature over Gadanki (13.5°N, 79.2°E) during the sudden stratospheric warming of 2009

Science.gov (United States)

Sridharan, S.; Raghunath, K.; Sathishkumar, S.; Nath, D.

2010-09-01

Rayleigh lidar observations at Gadanki (13.5°N, 79.2°E) show an enhancement of the nightly mean temperature by 10-15 K at altitudes 70-80 km and of gravity wave potential energy at 60-70 km during the 2009 major stratospheric warming event. An enhanced quasi-16-day wave activity is observed at 50-70 km in the wavelet spectrum of TIMED-SABER temperatures, possibly due to the absence of a critical level in the low-latitude stratosphere because of less westward winds caused by this warming event. The observed low-latitude mesospheric warming could be due to wave breaking, as waves are damped at 80 km.

Did European temperatures in 1540 exceed present-day records?

Science.gov (United States)

Orth, Rene; Vogel, Martha M.; Luterbacher, Jürg; Pfister, Christian; Seneviratne, Sonia I.

2017-04-01

There is strong evidence that the year 1540 was exceptionally dry and warm in Central Europe. Here we infer 1540 summer temperatures from the number of dry days (NDDs) in spring (March-May) and summer (June-August) in 1540 derived from historical documentary evidence published elsewhere, and compare our estimates with present-day temperatures. We translate the NDD values into temperature distributions using a linear relationship between modeled temperature and NDD from a 3000 year pre-industrial control simulation with the Community Earth System Model (CESM). Our results show medium confidence that summer mean temperatures (T JJA) and maximum temperatures (TXx) in Central Europe in 1540 were warmer than the respective present-day mean summer temperatures (assessed between 1966-2015). The model-based reconstruction suggests further that with a probability of 40%-70%, the highest daily temperatures in 1540 were even warmer than in 2003, while there is at most a 20% probability that the 1540 mean summer temperature was warmer than that of 2003 in Central Europe. As with other state-of-the-art analyses, the uncertainty of the reconstructed 1540 summer weather in this study is considerable, for instance as extrapolation is required because 1540-like events are not captured by the employed Earth system model (ESM), and neither by other ESMs. However, in addition to paleoclimatological approaches we introduce here an independent methodology to estimate 1540 temperatures, and contribute consequently to a reduced overall uncertainty in the analysis of this event. The characterization of such events and the related climate system functioning is particularly relevant in the context of global warming and the corresponding increase of extreme heat wave magnitude and occurrence frequency. Orth, R., M.M. Vogel, J. Luterbacher, C. Pfister, and S.I. Seneviratne, (2016): Did European temperatures in 1540 exceed present-day records? Env. Res. Lett., 11, 114021, doi: 10.1088/1748-9326/11/11/114021

Increased Air Temperature during Simulated Autumn Conditions Does Not Increase Photosynthetic Carbon Gain But Affects the Dissipation of Excess Energy in Seedlings of the Evergreen Conifer Jack Pine1[OA

Science.gov (United States)

Busch, Florian; Hüner, Norman P.A.; Ensminger, Ingo

2007-01-01

Temperature and daylength act as environmental signals that determine the length of the growing season in boreal evergreen conifers. Climate change might affect the seasonal development of these trees, as they will experience naturally decreasing daylength during autumn, while at the same time warmer air temperature will maintain photosynthesis and respiration. We characterized the down-regulation of photosynthetic gas exchange and the mechanisms involved in the dissipation of energy in Jack pine (Pinus banksiana) in controlled environments during a simulated summer-autumn transition under natural conditions and conditions with altered air temperature and photoperiod. Using a factorial design, we dissected the effects of daylength and temperature. Control plants were grown at either warm summer conditions with 16-h photoperiod and 22°C or conditions representing a cool autumn with 8 h/7°C. To assess the impact of photoperiod and temperature on photosynthesis and energy dissipation, plants were also grown under either cold summer (16-h photoperiod/7°C) or warm autumn conditions (8-h photoperiod/22°C). Photosynthetic gas exchange was affected by both daylength and temperature. Assimilation and respiration rates under warm autumn conditions were only about one-half of the summer values but were similar to values obtained for cold summer and natural autumn treatments. In contrast, photosynthetic efficiency was largely determined by temperature but not by daylength. Plants of different treatments followed different strategies for dissipating excess energy. Whereas in the warm summer treatment safe dissipation of excess energy was facilitated via zeaxanthin, in all other treatments dissipation of excess energy was facilitated predominantly via increased aggregation of the light-harvesting complex of photosystem II. These differences were accompanied by a lower deepoxidation state and larger amounts of β-carotene in the warm autumn treatment as well as by changes in

How does the dengue vector mosquito Aedes albopictus respond to global warming?

Science.gov (United States)

Jia, Pengfei; Chen, Xiang; Chen, Jin; Lu, Liang; Liu, Qiyong; Tan, Xiaoyue

2017-03-11

Global warming has a marked influence on the life cycle of epidemic vectors as well as their interactions with human beings. The Aedes albopictus mosquito as the vector of dengue fever surged exponentially in the last decade, raising ecological and epistemological concerns of how climate change altered its growth rate and population dynamics. As the global warming pattern is considerably uneven across four seasons, with a confirmed stronger effect in winter, an emerging need arises as to exploring how the seasonal warming effects influence the annual development of Ae. albopictus. The model consolidates a 35-year climate dataset and designs fifteen warming patterns that increase the temperature of selected seasons. Based on a recently developed mechanistic population model of Ae. albopictus, the model simulates the thermal reaction of blood-fed adults by systematically increasing the temperature from 0.5 to 5 °C at an interval of 0.5 °C in each warming pattern. The results show the warming effects are different across seasons. The warming effects in spring and winter facilitate the development of the species by shortening the diapause period. The warming effect in summer is primarily negative by inhibiting mosquito development. The warming effect in autumn is considerably mixed. However, these warming effects cannot carry over to the following year, possibly due to the fact that under the extreme weather in winter the mosquito fully ceases from development and survives in terms of diapause eggs. As the historical pattern of global warming manifests seasonal fluctuations, this study provides corroborating and previously ignored evidence of how such seasonality affects the mosquito development. Understanding this short-term temperature-driven mechanism as one chain of the transmission events is critical to refining the thermal reaction norms of the epidemic vector under global warming as well as developing effective mosquito prevention and control strategies.

A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650

Science.gov (United States)

Langdon, P. G.; Caseldine, C. J.; Croudace, I. W.; Jarvis, S.; Wastegård, S.; Crowford, T. C.

2011-05-01

Few studies currently exist that aim to validate a proxy chironomid-temperature reconstruction with instrumental temperature measurements. We used a reconstruction from a chironomid percentage abundance data set to produce quantitative summer temperature estimates since AD 1650 for NW Iceland through a transfer function approach, and validated the record against instrumental temperature measurements from Stykkishólmur in western Iceland. The core was dated through Pb-210, Cs-137 and tephra analyses (Hekla 1693) which produced a well-constrained dating model across the whole study period. Little catchment disturbance, as shown through geochemical (Itrax) and loss-on-ignition data, throughout the period further reinforce the premise that the chironomids were responding to temperature and not other catchment or within-lake variables. Particularly cold phases were identified between AD 1683-1710, AD 1765-1780 and AD 1890-1917, with relative drops in summer temperatures in the order of 1.5-2°C. The timing of these cold phases agree well with other evidence of cooler temperatures, notably increased extent of Little Ice Age (LIA) glaciers. Our evidence suggests that the magnitude of summer temperature cooling (1.5-2°C) was enough to force LIA Icelandic glaciers into their maximum Holocene extent, which is in accordance with previous modelling experiments for an Icelandic ice cap (Langjökull).

Chronic warming stimulates growth of marsh grasses more than mangroves in a coastal wetland ecotone.

Science.gov (United States)

Coldren, G A; Barreto, C R; Wykoff, D D; Morrissey, E M; Langley, J A; Feller, I C; Chapman, S K

2016-11-01

Increasing temperatures and a reduction in the frequency and severity of freezing events have been linked to species distribution shifts. Across the globe, mangrove ranges are expanding toward higher latitudes, likely due to diminishing frequency of freezing events associated with climate change. Continued warming will alter coastal wetland plant dynamics both above- and belowground, potentially altering plant capacity to keep up with sea level rise. We conducted an in situ warming experiment, in northeast Florida, to determine how increased temperature (+2°C) influences co-occurring mangrove and salt marsh plants. Warming was achieved using passive warming with three treatment levels (ambient, shade control, warmed). Avicennia germinans, the black mangrove, exhibited no differences in growth or height due to experimental warming, but displayed a warming-induced increase in leaf production (48%). Surprisingly, Distichlis spicata, the dominant salt marsh grass, increased in biomass (53% in 2013 and 70% in 2014), density (41%) and height (18%) with warming during summer months. Warming decreased plant root mass at depth and changed abundances of anaerobic bacterial taxa. Even while the poleward shift of mangroves is clearly controlled by the occurrences of severe freezes, chronic warming between these freeze events may slow the progression of mangrove dominance within ecotones. © 2016 by the Ecological Society of America.

Post-warm-up muscle temperature maintenance: blood flow contribution and external heating optimisation.

Science.gov (United States)

Raccuglia, Margherita; Lloyd, Alex; Filingeri, Davide; Faulkner, Steve H; Hodder, Simon; Havenith, George

2016-02-01

Passive muscle heating has been shown to reduce the drop in post-warm-up muscle temperature (Tm) by about 25% over 30 min, with concomitant sprint/power performance improvements. We sought to determine the role of leg blood flow in this cooling and whether optimising the heating procedure would further benefit post-warm-up T m maintenance. Ten male cyclists completed 15-min sprint-based warm-up followed by 30 min recovery. Vastus lateralis Tm (Tmvl) was measured at deep-, mid- and superficial-depths before and after the warm-up, and after the recovery period (POST-REC). During the recovery period, participants wore water-perfused trousers heated to 43 °C (WPT43) with either whole leg heating (WHOLE) or upper leg heating (UPPER), which was compared to heating with electrically heated trousers at 40 °C (ELEC40) and a non-heated control (CON). The blood flow cooling effect on Tmvl was studied comparing one leg with (BF) and without (NBF) blood flow. Warm-up exercise significantly increased Tmvl by ~3 °C at all depths. After the recovery period, BF Tmvl was lower (~0.3 °C) than NBF Tmvl at all measured depths, with no difference between WHOLE versus UPPER. WPT43 reduced the post-warm-up drop in deep-Tmvl (-0.12 °C ± 0.3 °C) compared to ELEC40 (-1.08 ± 0.4 °C) and CON (-1.3 ± 0.3 °C), whereas mid- and superficial-Tmvl even increased by 0.15 ± 0.3 and 1.1 ± 1.1 °C, respectively. Thigh blood flow contributes to the post-warm-up Tmvl decline. Optimising the external heating procedure and increasing heating temperature of only 3 °C successfully maintained and even increased T mvl, demonstrating that heating temperature is the major determinant of post-warm-up Tmvl cooling in this application.

Characterizing and attributing the warming trend in sea and land surface temperatures

NARCIS (Netherlands)

Estrada, Francisco; Martins, Luis Filipe; Perron, Pierre

2017-01-01

Because of low-frequency internal variability, the observed and underlying warming trends in temperature series can be markedly different. Important differences in the observed nonlinear trends in hemispheric temperature series suggest that the northern and southern hemispheres have responded

Recent summer precipitation trends in the Greater Horn of Africa and the emerging role of Indian Ocean sea surface temperature

Energy Technology Data Exchange (ETDEWEB)

Williams, A.P. [Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM (United States); University of California, Geography Department, Santa Barbara, CA (United States); Funk, Chris [University of California, Geography Department, Santa Barbara, CA (United States); U.S. Geological Survey, Earth Resources Observation and Science (EROS), Sioux Falls, SD (United States); Michaelsen, Joel [University of California, Geography Department, Santa Barbara, CA (United States); Rauscher, Sara A. [Los Alamos National Laboratory, Theoretical Division, Los Alamos, NM (United States); Robertson, Iain; Loader, Neil J. [Swansea University, Department of Geography, College of Science, Swansea (United Kingdom); Wils, Tommy H.G. [Rotterdam University, Department of Geography, Rotterdam (Netherlands); Koprowski, Marcin [Nicolaus Copernicus University, Laboratory of Dendrochronology, Institute of Ecology and Environment Protection, Torun (Poland); Eshetu, Zewdu [Ethiopian Institute of Agricultural Research, Forestry Research Centre, Addis Ababa (Ethiopia)

2012-11-15

We utilize a variety of climate datasets to examine impacts of two mechanisms on precipitation in the Greater Horn of Africa (GHA) during northern-hemisphere summer. First, surface-pressure gradients draw moist air toward the GHA from the tropical Atlantic Ocean and Congo Basin. Variability of the strength of these gradients strongly influences GHA precipitation totals and accounts for important phenomena such as the 1960s-1980s rainfall decline and devastating 1984 drought. Following the 1980s, precipitation variability became increasingly influenced by the southern tropical Indian Ocean (STIO) region. Within this region, increases in sea-surface temperature, evaporation, and precipitation are linked with increased exports of dry mid-tropospheric air from the STIO region toward the GHA. Convergence of dry air above the GHA reduces local convection and precipitation. It also produces a clockwise circulation response near the ground that reduces moisture transports from the Congo Basin. Because precipitation originating in the Congo Basin has a unique isotopic signature, records of moisture transports from the Congo Basin may be preserved in the isotopic composition of annual tree rings in the Ethiopian Highlands. A negative trend in tree-ring oxygen-18 during the past half century suggests a decline in the proportion of precipitation originating from the Congo Basin. This trend may not be part of a natural cycle that will soon rebound because climate models characterize Indian Ocean warming as a principal signature of greenhouse-gas induced climate change. We therefore expect surface warming in the STIO region to continue to negatively impact GHA precipitation during northern-hemisphere summer. (orig.)

Recent Global Warming As Depicted by AIRS, GISSTEMP, and MERRA-2

Science.gov (United States)

Susskind, J.; Iredell, L. F.; Lee, J. N.

2017-12-01

We observed anomalously warm global mean surface temperatures since 2015. The year 2016 represents the warmest annual mean surface skin and surface air temperatures in the AIRS observational period, September 2002 through August 2017. Additionally, AIRS monthly mean surface skin temperature, from January 2016 through September 2016, and November 2016, were the warmest observed for each month of the year. Continuing this trend, the AIRS global surface temperatures of 2017 February and April show the second greatest positive anomalies from average. This recent warming is particularly significant over the Arctic where the snow and sea ice melt is closely tied to the spring and summer surface temperatures. In this paper, we show the global distribution of surface temperature anomalies as observed by AIRS over the period September 2002 through August 2017 and compare them with those from the GISSTEMP and MERRA-2 surface temperatures. The spatial patterns of warm and cold anomalies for a given month show reasonably good agreement in all three data set. AIRS anomalies, which do not have the benefit of in-situ measurements, are in almost perfect agreement with those of MERRA-2, which does use in-situ surface measurements. GISSTEMP anomaly patterns for the most part look similar to those of AIRS and MERRA-2, but are more spread out spatially, and consequently are also weaker.

Soil warming increases metabolic quotients of soil microorganisms without changes in temperature sensitivity of soil respiration

Science.gov (United States)

Marañón-Jiménez, Sara; Soong, Jenniffer L.; Leblans, Niki I. W.; Sigurdsson, Bjarni D.; Dauwe, Steven; Fransen, Erik; Janssens, Ivan A.

2017-04-01

Increasing temperatures can accelerate soil organic matter (SOM) decomposition and release large amounts of CO2 to the atmosphere, potentially inducing climate change feedbacks. Alterations to the temperature sensitivity and metabolic pathways of soil microorganisms in response to soil warming can play a key role in these soil carbon (C) losses. Here, we present results of an incubation experiment using soils from a geothermal gradient in Iceland that have been subjected to different intensities of soil warming (+0, +1, +3, +5, +10 and +20 °C above ambient) over seven years. We hypothesized that 7 years of soil warming would led to a depletion of labile organic substrates, with a subsequent decrease of the "apparent" temperature sensitivity of soil respiration. Associated to this C limitation and more sub-optimal conditions for microbial growth, we also hypothesized increased microbial metabolic quotients (soil respiration per unit of microbial biomass), which is associated with increases in the relative amount of C invested into catabolic pathways along the warming gradient. Soil respiration and basal respiration rates decreased with soil warming intensity, in parallel with a decline in soil C availability. Contrasting to our first hypothesis, we did not detect changes in the temperature sensitivity of soil respiration with soil warming or on the availability of nutrients and of labile C substrates at the time of incubation. However, in agreement to our second hypothesis, microbial metabolic quotients (soil respiration per unit of microbial biomass) increased at warmer temperatures, while the C retained in biomass decreased as substrate became limiting. Long-term (7 years) temperature increases thus triggered a change in the metabolic functioning of the soil microbial communities towards increasing energy costs for maintenance or resource acquisition, thereby lowering the capacity of C retention and stabilization of warmed soils. These results highlight the need

Coherent climate anomalies over the Indo-western Pacific in post-El Niño summer

Science.gov (United States)

Kosaka, Y.; Xie, S. P.; DU, Y.; Hu, K.; Chowdary, J. S.; Huang, G.

2016-12-01

El Niño typically peaks in boreal winter, and the associated equatorial Pacific sea surface temperature (SST) signal dissipates before subsequent summer. Its impact, however, outlasts until boreal summer in the Indo-western Pacific, featuring basin-wide Indian Ocean warming and tropical Northwestern Pacific cooling accompanied by the Pacific-Japan (PJ) teleconnection pattern with surface anomalous anticyclone (AAC) extending from the Philippine Sea to the northern Indian Ocean. Two formation mechanisms have been proposed for these climate anomalies in post-El Niño-Southern Oscillation (ENSO) summer. One hypothesis invokes the wind-evaporation-SST (WES) feedback in the tropical Northwestern Pacific, while the other points to inter-basin feedback between the Indian Ocean and tropical Northwestern Pacific. Based on a coupled model experiment, we propose an ocean-atmosphere coupled mode that synthesizes the two mechanisms. This Indo-western Pacific Ocean capacitor (IPOC) mode evolves seasonally from spring to summer under seasonal migration of background state. In spring, the WES feedback is operative in association with the tropical Northwestern Pacific cooling, while in summer the Indian Ocean warming and the inter-basin interaction maintains the AAC. While the IPOC mode is independent of ENSO in mechanism, ENSO can drive this mode in its decay phase. This excitation, however, has undergone substantial interdecadal modulations, depending on ENSO amplitude and persistence of Indian Ocean warming. The ENSO-IPOC correlation is high after the mid-1970s and at the beginning of the 20th century, but low in between.

Tracing the Inter-Hemispheric Coupling During Polar Summer Periods of 2002-2010 Using TIMED/SABER Measurements

Science.gov (United States)

Goldberg, Richard; Feoflow, Artem; Pesnell, Dean; Kutepov, Alexander

2010-01-01

It has been found that for more than one polar summer season between 2002-2010, the northern polar mesospheric region near and above the mesospheric maximum was warmer than normal. The strongest warming effect of this type was observed to occur during northern summer 2002. Theoretical studies have implied that these "anomalies" were preceded by unusual dynamical processes occurring in the southern hemisphere. We have analyzed temperature distributions measured by the SABER limb scanning infrared radiometer aboard the NASA TIMED satellite between 2002-2010 at altitudes from 15 to 110 km and for latitudes between 83 deg. S to 83 deg. N. We describe the approach to trace the inter-hemispheric temperature correlatoins and to identify the global features that were unique for the "anomalous" northern polar summers.

Ecosystem maturation follows the warming of the Arctic fjords

OpenAIRE

Jan Marcin Węsławski; Friedrich Buchholz; Marta Głuchowska; Agata Weydmann

2017-01-01

Two fjords in West Spitsbergen (Hornsund 77°N and Kongsfjorden 79°N) differ with regard to their exposure towards increasingly warm Atlantic water inflow. Hornsund remains in many respects cooler than Kongsfjorden (on average 2°C SST in summer) and is less influenced by warmer and more saline Atlantic waters. Reported changes in the physical environment (temperature rise, freshwater inflow, salinity drop, turbidity, fast-ice reduction, coastal change) are discussed in the context of biologica...

Relationship between alpine tourism demand and hot summer air temperatures associated with climate change

Science.gov (United States)

Rebetez, M.; Serquet, G.

2010-09-01

We quantified the impacts of hot summer air temperatures on tourism in the Swiss Alps by analyzing the relationship between temperature and overnight stays in 40 Alpine resorts. Several temperature and insolation thresholds were tested to detect their relationship to summer tourism. Our results reveal significant correlations between the number of nights spent in mountain resorts and hot temperatures at lower elevations. Alpine resorts nearest to cities are most sensitive to hot temperatures. This is probably because reactions to hot episodes take place on a short-term basis as heat waves remain relatively rare. The correlation in June is stronger compared to the other months, probably because school holidays and the peak domestic tourist demand in summer usually takes place in July and August. Our results suggest that alpine tourist resorts could benefit from hotter temperatures at lower elevations under future climates. Tourists already react on a short-term basis to hot days and spend more nights in hotels in mountain resorts. If heat waves become more regular, it seems likely that tourists choose to stay at alpine resorts more frequently and for longer periods.

Passive warming effect on soil microbial community and humic substance degradation in maritime Antarctic region.

Science.gov (United States)

Kim, Dockyu; Park, Ha Ju; Kim, Jung Ho; Youn, Ui Joung; Yang, Yung Hun; Casanova-Katny, Angélica; Vargas, Cristina Muñoz; Venegas, Erick Zagal; Park, Hyun; Hong, Soon Gyu

2018-06-01

Although the maritime Antarctic has undergone rapid warming, the effects on indigenous soil-inhabiting microorganisms are not well known. Passive warming experiments using open-top chamber (OTC) have been performed on the Fildes Peninsula in the maritime Antarctic since 2008. When the soil temperature was measured at a depth of 2-5 cm during the 2013-2015 summer seasons, the mean temperature inside OTC (OTC-In) increased by approximately 0.8 °C compared with outside OTC (OTC-Out), while soil chemical and physical characteristics did not change. Soils (2015 summer) from OTC-In and OTC-Out were subjected to analysis for change in microbial community and degradation rate of humic substances (HS, the largest pool of recalcitrant organic carbon in soil). Archaeal and bacterial communities in OTC-In were minimally affected by warming compared with those in OTC-Out, with archaeal methanogenic Thermoplasmata slightly increased in abundance. The abundance of heterotrophic fungi Ascomycota was significantly altered in OTC-In. Total bacterial and fungal biomass in OTC-In increased by 20% compared to OTC-Out, indicating that this may be due to increased microbial degradation activity for soil organic matter (SOM) including HS, which would result in the release of more low-molecular-weight growth substrates from SOM. Despite the effects of warming on the microbial community over the 8-years-experiments warming did not induce any detectable change in content or structure of polymeric HS. These results suggest that increased temperature may have significant and direct effects on soil microbial communities inhabiting maritime Antarctic and that soil microbes would subsequently provide more available carbon sources for other indigenous microbes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature response of soil respiration largely unaltered with experimental warming

NARCIS (Netherlands)

Carey, J.C.; Tang, J.; Templer, P.H.; Kroeger, K.D.; Crowther, T.W.; Burton, A.J.; Dukes, J.S.; Emmett, B.; Frey, S.D.; Heskel, M.A.; Jiang, L.; Machmuller, M.B.; Mohan, J.; Panetta, A.M.; Reich, P.B.; Reinsch, S.; Wang, X.; Allison, S.D.; Bamminger, C.; Bridgham, S.; Collins, S.L.; de Dato, G.; Eddy, W.C.; Enquist, B.J.; Estiarte, M.; Harte, J.; Henderson, A.; Johnson, B.R.; Larsen, K.S.; Luo, Y.; Marhan, S.; Melillo, J.M.; Peñuelas, J.; Pfeifer-Meister, L.; Poll, C.; Rastetter, E.; Reinmann, A.B.; Reynolds, L.L.; Schmidt, I.K.; Shaver, G.R.; Strong, A.L.; Suseela, V.; Tietema, A.

2016-01-01

The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific

Coping with temperature at the warm edge--patterns of thermal adaptation in the microbial eukaryote Paramecium caudatum.

Directory of Open Access Journals (Sweden)

Sascha Krenek

Full Text Available Ectothermic organisms are thought to be severely affected by global warming since their physiological performance is directly dependent on temperature. Latitudinal and temporal variations in mean temperatures force ectotherms to adapt to these complex environmental conditions. Studies investigating current patterns of thermal adaptation among populations of different latitudes allow a prediction of the potential impact of prospective increases in environmental temperatures on their fitness.In this study, temperature reaction norms were ascertained among 18 genetically defined, natural clones of the microbial eukaryote Paramecium caudatum. These different clones have been isolated from 12 freshwater habitats along a latitudinal transect in Europe and from 3 tropical habitats (Indonesia. The sensitivity to increasing temperatures was estimated through the analysis of clone specific thermal tolerances and by relating those to current and predicted temperature data of their natural habitats. All investigated European clones seem to be thermal generalists with a broad thermal tolerance and similar optimum temperatures. The weak or missing co-variation of thermal tolerance with latitude does not imply local adaptation to thermal gradients; it rather suggests adaptive phenotypic plasticity among the whole European subpopulation. The tested Indonesian clones appear to be locally adapted to the less variable, tropical temperature regime and show higher tolerance limits, but lower tolerance breadths.Due to the lack of local temperature adaptation within the European subpopulation, P. caudatum genotypes at the most southern edge of their geographic range seem to suffer from the predicted increase in magnitude and frequency of summer heat waves caused by climate change.

Establishment and verification of solar radiation calculation model of glass daylighting roof in hot summer and warm winter zone in China

OpenAIRE

Zheng, Caidan; Wu, Peihao; Costanzo, Vincenzo; Wang, Yuchen; Yang, Xiaokun

2017-01-01

In this paper, solar heat gain through glass daylighting roof is deeply studied by theoretical calculation method, taking Guangzhou in the Hot Summer and Warm Winter (HSWW) zone as an example. The direct solar radiation is calculated by Bouguer formula whereas the diffuse solar radiation is calculated by Berlage formula, representing the basis for the calculation method of the solar radiation intensity through the glass daylighting roof. Through the establishment of solar radiation calculatio...

Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time.

Science.gov (United States)

Elmendorf, Sarah C; Henry, Gregory H R; Hollister, Robert D; Björk, Robert G; Bjorkman, Anne D; Callaghan, Terry V; Collier, Laura Siegwart; Cooper, Elisabeth J; Cornelissen, Johannes H C; Day, Thomas A; Fosaa, Anna Maria; Gould, William A; Grétarsdóttir, Járngerður; Harte, John; Hermanutz, Luise; Hik, David S; Hofgaard, Annika; Jarrad, Frith; Jónsdóttir, Ingibjörg Svala; Keuper, Frida; Klanderud, Kari; Klein, Julia A; Koh, Saewan; Kudo, Gaku; Lang, Simone I; Loewen, Val; May, Jeremy L; Mercado, Joel; Michelsen, Anders; Molau, Ulf; Myers-Smith, Isla H; Oberbauer, Steven F; Pieper, Sara; Post, Eric; Rixen, Christian; Robinson, Clare H; Schmidt, Niels Martin; Shaver, Gaius R; Stenström, Anna; Tolvanen, Anne; Totland, Orjan; Troxler, Tiffany; Wahren, Carl-Henrik; Webber, Patrick J; Welker, Jeffery M; Wookey, Philip A

2012-02-01

Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date. © 2011 Blackwell Publishing Ltd/CNRS.

Twentieth-century warming revives the world's northernmost lake

DEFF Research Database (Denmark)

Perren, Bianca B.; Wolfe, Alexander P.; Cooke, Colin A.

2012-01-01

lake to explore this question. Microfossils indicate that siliceous diatoms and chrysophytes were abundant initially, but disappeared 2400 yr ago in concert with Neoglacial cooling. Microfossils reappear in 20th-century sediments and reach unprecedented concentrations in sediments deposited after ca. A.......D. 1980, tracking increasing summer temperatures in the absence of evidence for atmospheric nutrient subsidies. These results indicate that current warming in northern Greenland is unprecedented in the context of the past 2400 yr, and that climate change alone is responsible for the marked biological...

Human influence on Canadian temperatures

Science.gov (United States)

Wan, Hui; Zhang, Xuebin; Zwiers, Francis

2018-02-01

Canada has experienced some of the most rapid warming on Earth over the past few decades with a warming rate about twice that of the global mean temperature since 1948. Long-term warming is observed in Canada's annual, winter and summer mean temperatures, and in the annual coldest and hottest daytime and nighttime temperatures. The causes of these changes are assessed by comparing observed changes with climate model simulated responses to anthropogenic and natural (solar and volcanic) external forcings. Most of the observed warming of 1.7 °C increase in annual mean temperature during 1948-2012 [90% confidence interval (1.1°, 2.2 °C)] can only be explained by external forcing on the climate system, with anthropogenic influence being the dominant factor. It is estimated that anthropogenic forcing has contributed 1.0 °C (0.6°, 1.5 °C) and natural external forcing has contributed 0.2 °C (0.1°, 0.3 °C) to the observed warming. Up to 0.5 °C of the observed warming trend may be associated with low frequency variability of the climate such as that represented by the Pacific decadal oscillation (PDO) and North Atlantic oscillation (NAO). Overall, the influence of both anthropogenic and natural external forcing is clearly evident in Canada-wide mean and extreme temperatures, and can also be detected regionally over much of the country.

Climate warming could increase recruitment success in glacier foreland plants.

Science.gov (United States)

Mondoni, Andrea; Pedrini, Simone; Bernareggi, Giulietta; Rossi, Graziano; Abeli, Thomas; Probert, Robin J; Ghitti, Michele; Bonomi, Costantino; Orsenigo, Simone

2015-11-01

Glacier foreland plants are highly threatened by global warming. Regeneration from seeds on deglaciated terrain will be crucial for successful migration and survival of these species, and hence a better understanding of the impacts of climate change on seedling recruitment is urgently needed to predict future plant persistence in these environments. This study presents the first field evidence of the impact of climate change on recruitment success of glacier foreland plants. Seeds of eight foreland species were sown on a foreland site at 2500 m a.s.l., and at a site 400 m lower in altitude to simulate a 2·7 °C increase in mean annual temperature. Soil from the site of origin was used to reproduce the natural germination substrate. Recruitment success, temperature and water potential were monitored for 2 years. The response of seed germination to warming was further investigated in the laboratory. At the glacier foreland site, seedling emergence was low (0 to approx. 40 %) and occurred in summer in all species after seeds had experienced autumn and winter seasons. However, at the warmer site there was a shift from summer to autumn emergence in two species and a significant increase of summer emergence (13-35 % higher) in all species except two. Survival and establishment was possible for 60-75 % of autumn-emerged seedlings and was generally greater under warmer conditions. Early snowmelt in spring caused the main ecological factors enhancing the recruitment success. The results suggest that warming will influence the recruitment of glacier foreland species primarily via the extension of the snow-free period in spring, which increases seedling establishment and results in a greater resistance to summer drought and winter extremes. The changes in recruitment success observed here imply that range shifts or changes in abundance are possible in a future warmer climate, but overall success may be dependent on interactions with shifts in other components of the

Warming Trends and Bleaching Stress of the World’s Coral Reefs 1985-2012

Science.gov (United States)

Heron, Scott F.; Maynard, Jeffrey A.; van Hooidonk, Ruben; Eakin, C. Mark

2016-12-01

Coral reefs across the world’s oceans are in the midst of the longest bleaching event on record (from 2014 to at least 2016). As many of the world’s reefs are remote, there is limited information on how past thermal conditions have influenced reef composition and current stress responses. Using satellite temperature data for 1985-2012, the analysis we present is the first to quantify, for global reef locations, spatial variations in warming trends, thermal stress events and temperature variability at reef-scale (~4 km). Among over 60,000 reef pixels globally, 97% show positive SST trends during the study period with 60% warming significantly. Annual trends exceeded summertime trends at most locations. This indicates that the period of summer-like temperatures has become longer through the record, with a corresponding shortening of the ‘winter’ reprieve from warm temperatures. The frequency of bleaching-level thermal stress increased three-fold between 1985-91 and 2006-12 - a trend climate model projections suggest will continue. The thermal history data products developed enable needed studies relating thermal history to bleaching resistance and community composition. Such analyses can help identify reefs more resilient to thermal stress.

Incorporating residual temperature and specific humidity in predicting weather-dependent warm-season electricity consumption

Science.gov (United States)

Guan, Huade; Beecham, Simon; Xu, Hanqiu; Ingleton, Greg

2017-02-01

Climate warming and increasing variability challenges the electricity supply in warm seasons. A good quantitative representation of the relationship between warm-season electricity consumption and weather condition provides necessary information for long-term electricity planning and short-term electricity management. In this study, an extended version of cooling degree days (ECDD) is proposed for better characterisation of this relationship. The ECDD includes temperature, residual temperature and specific humidity effects. The residual temperature is introduced for the first time to reflect the building thermal inertia effect on electricity consumption. The study is based on the electricity consumption data of four multiple-street city blocks and three office buildings. It is found that the residual temperature effect is about 20% of the current-day temperature effect at the block scale, and increases with a large variation at the building scale. Investigation of this residual temperature effect provides insight to the influence of building designs and structures on electricity consumption. The specific humidity effect appears to be more important at the building scale than at the block scale. A building with high energy performance does not necessarily have low specific humidity dependence. The new ECDD better reflects the weather dependence of electricity consumption than the conventional CDD method.

Poleward shift and weakening of summer season synoptic activity over India in a warming climate

Science.gov (United States)

Ravindran, A. M.; Sandeep, S.; Boos, W. R.; TP, S.; Praveen, V.

2017-12-01

One of the main components of the Indian summer monsoon is the presence of low intensity cyclonic systems popularly known as Low Pressure Systems (LPS), which contribute more than half of the precipitation received over the fertile Central Indian region. An average of 13 (±2.5) storms develop each boreal summer, with most originating over the Bay of Bengal (BoB) and adjoining land. These systems typically follow a north-west track along the monsoon trough. Despite its significance, the future variability of these storms is not studied, due to the inadequate representation of these systems in current generation climate models. A series of numerical experiments are performed here using the High Resolution Atmospheric Model (HiRAM) with a horizontal grid spacing of 50 km globally to simulate these rain-bearing systems. One set of simulations represents the historical (HIST) period and the other a late 21st century climate scenario based on the strongest Representative Concentration Pathway (RCP8.5). Four ensemble members of these simulations are run, with sea surface temperatures (SSTs) taken from different CMIP5 GCMs selected for their skill in simulating the Indian monsoon. In addition, ten ensemble members of `decadal' experiments are run for both HIST and RCP8.5 to assess model uncertainty, in which the model is forced with annual cycles of decadal mean SSTs. We show that the strength of monsoon LPS activity would decline as much as 50% by the end of the 21st century, under business as usual emission scenario. The overall reduction in the LPS activity is contributed by a 60% decrease in the frequency of storms over the Bay of Bengal, while the weaker systems that form over the land has increased 10% in a warmer climate. Further analysis suggests that a relatively slower rate of warming over the Bay of Bengal compared to the surrounding regions has resulted in an enhanced moist stability over the main genesis region of LPS, which in turn suppressed the growth of

Stratospheric Temperature Trends Observed by TIMED/SABER

Science.gov (United States)

Xian, T.; Tan, R.

2017-12-01

Trends in the stratospheric temperature are studied based on the temperature profile observation from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). The spatially trends are evaluated in different time scales ranging from decadal to monthly resolved. The results indicate a signature of BDC acceleration. There are strong warming trends (up to 9 K/decade) in the middle to upper stratosphere in the high latitude spring, summer, and autumn seasons, accompanied by strong cooling trends in the lower stratosphere. Besides, strong warming trends occurs through the whole stratosphere over the Southern Hemisphere, which confirms Antarctic ozone layer healing since 2000. In addition, the results demonstrate a significant warming trends in the middle of tropical stratosphere, which becomes strongest during June-July-August.

Summer temperature and spatial variability of all-cause mortality in Surat city, India

Directory of Open Access Journals (Sweden)

S K Rathi

2017-01-01

Full Text Available Background: Ample information is available on extreme heat associated mortality for few Indian cities, but scant literature is available on effect of temperature on spatial variability of all-cause mortality for coastal cities. Objective: To assess the effect of daily maximum temperature, relative humidity and heat index on spatial variability of all-cause mortality for summer months (March to May from 2014 to 2015 for the urban population of Surat (coastal city. Materials and Methods: Retrospective analysis of the all-cause mortality data with temperature and humidity was performed on a total of 9,237 deaths for 184 summer days (2014-2015. Climatic and all-cause mortality data were obtained through Tutiempo website and Surat Municipal Corporation respectively. Bivariate analysis performed through SPSS. Observations: Mean daily mortality was estimated at 50.2 ± 8.5 for the study period with a rise of 20% all-cause mortality at temperature ≥ 40°C and rise of 10% deaths per day during extreme danger level (HI: > 54°C days. Spatial (Zone wise analysis revealed rise of 61% all-cause mortality for Southeast and 30% for East zones at temperature ≥ 40°C. Conclusions: All-cause mortality increased on high summer temperature days. Presence of spatial variation in all-cause mortality provided the evidence for high risk zones. Findings may be helpful in designing the interventions at micro level.

Does the recent warming hiatus exist over northern Asia for winter wind chill temperature?

Science.gov (United States)

Ma, Ying

2017-04-01

Wind chill temperature (WCT) describes the joint effect of wind velocity and air temperature on exposed body skin and could support policy makers in designing plans to reduce the risks of notably cold and windy weather. This study examined winter WCT over northern Asia during 1973-2013 by analyzing in situ station data. The winter WCT warming rate over the Tibetan Plateau slowed during 1999-2013 (-0.04 °C/decade) compared with that during 1973-1998 (0.67 °C/decade). The winter WCT warming hiatus has also been observed in the remainder of Northern Asia with trends of 1.11 °C/decade during 1973-1998 but -1.02 °C/decade during 1999-2013, except for the Far East of Russia (FE), where the winter WCT has continued to heat up during both the earlier period of 1973-1998 (0.54 °C/decade) and the recent period of 1999-2013 (0.75 °C/decade). The results indicate that the influence of temperature on winter WCT is greater than that of wind speed over northern Asia. Atmospheric circulation changes associated with air temperature and wind speed were analyzed to identify the causes for the warming hiatus of winter WCT over northern Asia. The distributions of sea level pressure and 500 hPa height anomalies during 1999-2013 transported cold air from the high latitudes to middle latitudes, resulting in low air temperature over Northern Asia except for the Far East of Russia. Over the Tibetan Plateau, the increase in wind speed offset the increase in air temperature during 1999-2013. For the Far East, the southerly wind from the Western Pacific drove the temperature up during the 1999-2013 period via warm advection.

The time of day effects of warm temperature on flowering time involve PIF4 and PIF5

Science.gov (United States)

Thines, Bryan C.; Duarte, Maritza I.; Harmon, Frank G.

2014-01-01

Warm temperature promotes flowering in Arabidopsis thaliana and this response involves multiple signalling pathways. To understand the temporal dynamics of temperature perception, tests were carried out to determine if there was a daily window of enhanced sensitivity to warm temperature (28 °C). Warm temperature applied during daytime, night-time, or continuously elicited earlier flowering, but the effects of each treatment were unequal. Plants exposed to warm night (WN) conditions flowered nearly as early as those in constant warm (CW) conditions, while treatment with warm days (WD) caused later flowering than either WN or CW. Flowering in each condition relied to varying degrees on the activity of CO , FT , PIF4 , and PIF5 , as well as the action of unknown genes. The combination of signalling pathways involved in flowering depended on the time of the temperature cue. WN treatments caused a significant advance in the rhythmic expression waveform of CO, which correlated with pronounced up-regulation of FT expression, while WD caused limited changes in CO expression and no stimulation of FT expression. WN- and WD-induced flowering was partially CO independent and, unexpectedly, dependent on PIF4 and PIF5 . pif4-2, pif5-3, and pif4-2 pif5-3 mutants had delayed flowering under all three warm conditions. The double mutant was also late flowering in control conditions. In addition, WN conditions alone imposed selective changes to PIF4 and PIF5 expression. Thus, the PIF4 and PIF5 transcription factors promote flowering by at least two means: inducing FT expression in WN and acting outside of FT by an unknown mechanism in WD. PMID:24574484

Large ground warming in the Canadian Arctic inferred from inversions of temperature logs

Czech Academy of Sciences Publication Activity Database

Majorowicz, J. A.; Skinner, W. R.; Šafanda, Jan

2004-01-01

Roč. 221, č. 1 (2004), s. 15-25 ISSN 0012-821X Institutional research plan: CEZ:AV0Z3012916 Keywords : global warming * borehole temperatures * ground temperatures Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 3.499, year: 2004

How El-Nino affects Ethiopian summer rainfall

Science.gov (United States)

Gleixner, Stephanie; Keenlyside, Noel; Viste, Ellen

2016-04-01

Ethiopian economy and society are strongly dependent on agriculture and therefore rainfall. Reliable forecasts for the rainy seasons are important to allow for agricultural planning and drought preparations. The operational seasonal forecasts for Ethiopia are based on analogue methods relying mainly on sea surface temperature (SST) indices. A better understanding of the physical links between Ethiopian rainfall and SST may help to improve forecasts. The highest rainfall rates are observed in the Kiremt season (defined as JJAS), which is the rainy season in Central and Northwestern Ethiopia. Kiremt rainfall shows clear negative correlation with Central Pacific SST, linking dry Ethiopian summers with ENSO-like warm SST anomalies. We use the atmosphere general circulation model Echam5.3 to investigate the physical link between Pacific SST anomalies and Kiremt rainfall. We compare a historical simulation with a T106 horizontal resolution (~ 1.125°), forced with reconstructed SST data, to gauge-based rainfall observations for the time period of 1961 to 2009. Composite analysis for model and observations show warm SST anomalies in the Central Pacific and a corresponding large-scale circulation anomaly with subsidence over Ethiopia in dry Kiremt seasons. Horizontal wind fields show a slow-down of the whole Indian monsoon system with a weaker Tropical Easterly Jet (TEJ) and a weaker East African Low-Level Jet (EALLJ) in these summers. We conducted a sensitivity experiment with El Nino like SST anomalies in the Central Pacific with the same Echam version. Its results show that warm Pacific SST anomalies cause dry summer conditions over Ethiopia. While the large-scale subsidence over East Africa is present in the experiment, there is no significant weakening of the Indian monsoon system. We rather find an anomalous circulation cell over Northern Africa with westerlies at 100-200 hPa and easterlies below 500 hPa. The anomalous easterly flow in the lower and middle

Summer monsoon circulation and precipitation over the tropical Indian Ocean during ENSO in the NCEP climate forecast system

Science.gov (United States)

Chowdary, J. S.; Chaudhari, H. S.; Gnanaseelan, C.; Parekh, Anant; Suryachandra Rao, A.; Sreenivas, P.; Pokhrel, S.; Singh, P.

2014-04-01

This study investigates the El Niño Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) and their relationship with the Indian summer monsoon in the coupled general circulation model climate forecast system (CFS). The model shows good skill in simulating the impact of El Niño over the Indian Oceanic rim during its decay phase (the summer following peak phase of El Niño). Summer surface circulation patterns during the developing phase of El Niño are more influenced by local Sea Surface Temperature (SST) anomalies in the model unlike in observations. Eastern TIO cooling similar to that of Indian Ocean Dipole (IOD) is a dominant model feature in summer. This anomalous SST pattern therefore is attributed to the tendency of the model to simulate more frequent IOD events. On the other hand, in the model baroclinic response to the diabatic heating anomalies induced by the El Niño related warm SSTs is weak, resulting in reduced zonal extension of the Rossby wave response. This is mostly due to weak eastern Pacific summer time SST anomalies in the model during the developing phase of El Niño as compared to observations. Both eastern TIO cooling and weak SST warming in El Niño region combined together undermine the ENSO teleconnections to the TIO and south Asia regions. The model is able to capture the spatial patterns of SST, circulation and precipitation well during the decay phase of El Niño over the Indo-western Pacific including the typical spring asymmetric mode and summer basin-wide warming in TIO. The model simulated El Niño decay one or two seasons later, resulting long persistent warm SST and circulation anomalies mainly over the southwest TIO. In response to the late decay of El Niño, Ekman pumping shows two maxima over the southern TIO. In conjunction with this unrealistic Ekman pumping, westward propagating Rossby waves display two peaks, which play key role in the long-persistence of the TIO warming in the model (for more than a

Summer U.S. Surface Air Temperature Variability: Controlling Factors and AMIP Simulation Biases

Science.gov (United States)

Merrifield, A.; Xie, S. P.

2016-02-01

This study documents and investigates biases in simulating summer surface air temperature (SAT) variability over the continental U.S. in the Coupled Model Intercomparison Project (CMIP5) Atmospheric Model Intercomparison Project (AMIP). Empirical orthogonal function (EOF) and multivariate regression analyses are used to assess the relative importance of circulation and the land surface feedback at setting summer SAT over a 30-year period (1979-2008). In observations, regions of high SAT variability are closely associated with midtropospheric highs and subsidence, consistent with adiabatic theory (Meehl and Tebaldi 2004, Lau and Nath 2012). Preliminary analysis shows the majority of the AMIP models feature high SAT variability over the central U.S., displaced south and/or west of observed centers of action (COAs). SAT COAs in models tend to be concomitant with regions of high sensible heat flux variability, suggesting an excessive land surface feedback in these models modulate U.S. summer SAT. Additionally, tropical sea surface temperatures (SSTs) play a role in forcing the leading EOF mode for summer SAT, in concert with internal atmospheric variability. There is evidence that models respond to different SST patterns than observed. Addressing issues with the bulk land surface feedback and the SST-forced component of atmospheric variability may be key to improving model skill in simulating summer SAT variability over the U.S.

A New Wave of Permafrost Warming in the Alaskan Interior?

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Romanovsky, V. E.; Nicolsky, D.; Cable, W.; Kholodov, A. L.; Panda, S. K.

2017-12-01

The impact of climate warming on permafrost and the potential of climate feedbacks resulting from permafrost thawing have recently received a great deal of attention. Ground temperatures are a primary indicator of permafrost stability. Many of the research sites in our permafrost network are located along the North American Arctic Permafrost-Ecological Transect that spans all permafrost zones in Alaska. Most of the sites in Alaska show substantial warming of permafrost since the 1980s. The magnitude of warming has varied with location, but was typically from 0.5 to 3°C. However, this warming was not linear in time and not spatially uniform. In some regions this warming even may be reversed and a slight recent cooling of permafrost has been observed recently at some locations. The Interior of Alaska is one of such regions where a slight permafrost cooling was observed starting in the late 1990s that has continued through the 2000s and in the beginning of the 2010s. The cooling has followed the substantial increase in permafrost temperatures documented for the Interior during the 1980s and 1990s. Permafrost temperatures at 15 m depth increased here by 0.3 to 0.6°C between 1983 and 1996. In most locations they reached their maximum in the second half of the 1990s. Since then, the permafrost temperatures started to decrease slowly and by 2013 this decrease at some locations was as much as 0.3°C at 15 m depth. There are some indications that the warming trend in the Alaskan Interior permafrost resumed during the last four years. By 2016, new record highs for the entire period of measurements of permafrost temperatures at 15 m depth were recorded at several locations. The latest observed permafrost warming in the Interior was combined with higher than normal summer precipitations. This combination has triggered near-surface permafrost degradation in many locations with adverse consequences for the ground surface stability affecting ecosystems and infrastructure. In

Meta-analysis of warmed versus standard temperature CO2 insufflation for laparoscopic cholecystectomy.

Science.gov (United States)

Hakeem, Abdul R; Birks, Theodore; Azeem, Qasim; Di Franco, Filippo; Gergely, Szabolcs; Harris, Adrian M

2016-06-01

There is conflicting evidence for the use of warmed, humidified carbon dioxide (CO2) for creating pneumoperitoneum during laparoscopic cholecystectomy. Few studies have reported less post-operative pain and analgesic requirement when warmed CO2 was used. This systematic review and meta-analysis aims to analyse the literature on the use of warmed CO2 in comparison to standard temperature CO2 during laparoscopic cholecystectomy. Systematic review and meta-analysis carried out in line with the PRISMA guidelines. Primary outcomes of interest were post-operative pain at 6 h, day 1 and day 2 following laparoscopic cholecystectomy. Secondary outcomes were analgesic usage and drop in intra-operative core body temperature. Standard Mean Difference (SMD) was calculated for continuous variables. Six randomised controlled trials (RCTs) met the inclusion criteria (n = 369). There was no significant difference in post-operative pain at 6 h [3 RCTs; SMD = -0.66 (-1.33, 0.02) (Z = 1.89) (P = 0.06)], day 1 [4 RCTs; SMD = -0.51 (-1.47, 0.44) (Z = 1.05) (P = 0.29)] and day 2 [2 RCTs; SMD = -0.96 (-2.30, 0.37) (Z = 1.42) (P = 0.16)] between the warmed CO2 and standard CO2 group. There was no difference in analgesic usage between the two groups, but pooled analysis was not possible. Two RCTs reported significant drop in intra-operative core body temperature, but there were no adverse events related to this. This review showed no difference in post-operative pain and analgesic requirements between the warmed and standard CO2 insufflation during laparoscopic cholecystectomy. Currently there is not enough high quality evidence to suggest routine usage of warmed CO2 for creating pneumoperitoneum during laparoscopic cholecystectomy. Copyright © 2015 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.

Dynamical and thermodynamical coupling between the North Atlantic subtropical high and the marine boundary layer clouds in boreal summer

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Wei, Wei; Li, Wenhong; Deng, Yi; Yang, Song; Jiang, Jonathan H.; Huang, Lei; Liu, W. Timothy

2018-04-01

This study investigates dynamical and thermodynamical coupling between the North Atlantic subtropical high (NASH), marine boundary layer (MBL) clouds, and the local sea surface temperatures (SSTs) over the North Atlantic in boreal summer for 1984-2009 using NCEP/DOE Reanalysis 2 dataset, various cloud data, and the Hadley Centre sea surface temperature. On interannual timescales, the summer mean subtropical MBL clouds to the southeast of the NASH is actively coupled with the NASH and local SSTs: a stronger (weaker) NASH is often accompanied with an increase (a decrease) of MBL clouds and abnormally cooler (warmer) SSTs along the southeast flank of the NASH. To understand the physical processes between the NASH and the MBL clouds, the authors conduct a data diagnostic analysis and implement a numerical modeling investigation using an idealized anomalous atmospheric general circulation model (AGCM). Results suggest that significant northeasterly anomalies in the southeast flank of the NASH associated with an intensified NASH tend to induce stronger cold advection and coastal upwelling in the MBL cloud region, reducing the boundary surface temperature. Meanwhile, warm advection associated with the easterly anomalies from the African continent leads to warming over the MBL cloud region at 700 hPa. Such warming and the surface cooling increase the atmospheric static stability, favoring growth of the MBL clouds. The anomalous diabatic cooling associated with the growth of the MBL clouds dynamically excites an anomalous anticyclone to its north and contributes to strengthening of the NASH circulation in its southeast flank. The dynamical and thermodynamical couplings and their associated variations in the NASH, MBL clouds, and SSTs constitute an important aspect of the summer climate variability over the North Atlantic.

Daytime warming has stronger negative effects on soil nematodes than night-time warming

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Yan, Xiumin; Wang, Kehong; Song, Lihong; Wang, Xuefeng; Wu, Donghui

2017-03-01

Warming of the climate system is unequivocal, that is, stronger warming during night-time than during daytime. Here we focus on how soil nematodes respond to the current asymmetric warming. A field infrared heating experiment was performed in the western of the Songnen Plain, Northeast China. Three warming modes, i.e. daytime warming, night-time warming and diurnal warming, were taken to perform the asymmetric warming condition. Our results showed that the daytime and diurnal warming treatment significantly decreased soil nematodes density, and night-time warming treatment marginally affected the density. The response of bacterivorous nematode and fungivorous nematode to experimental warming showed the same trend with the total density. Redundancy analysis revealed an opposite effect of soil moisture and soil temperature, and the most important of soil moisture and temperature in night-time among the measured environment factors, affecting soil nematode community. Our findings suggested that daily minimum temperature and warming induced drying are most important factors affecting soil nematode community under the current global asymmetric warming.

Projecting future summer mortality due to ambient ozone concentration and temperature changes

Science.gov (United States)

Lee, Jae Young; Lee, Soo Hyun; Hong, Sung-Chul; Kim, Ho

2017-05-01

Climate change is known to affect the human health both directly by increased heat stress and indirectly by altering environments, particularly by altering the rate of ambient ozone formation in the atmosphere. Thus, the risks of climate change may be underestimated if the effects of both future temperature and ambient ozone concentrations are not considered. This study presents a projection of future summer non-accidental mortality in seven major cities of South Korea during the 2020s (2016-2025) and 2050s (2046-2055) considering changes in temperature and ozone concentration, which were predicted by using the HadGEM3-RA model and Integrated Climate and Air Quality Modeling System, respectively. Four Representative Concentration Pathway (RCP) scenarios (RCP 2.6, 4.5, 6.0, and 8.5) were considered. The result shows that non-accidental summer mortality will increase by 0.5%, 0.0%, 0.4%, and 0.4% in the 2020s, 1.9%, 1.5%, 1.2%, and 4.4% in the 2050s due to temperature change compared to the baseline mortality during 2001-2010, under RCP 2.6, 4.5, 6.0, and 8.5, respectively, whereas the mortality will increase by 0.0%, 0.5%, 0.0%, and 0.5% in the 2020s, and 0.2%, 0.2%, 0.4%, and 0.6% in the 2050s due to ozone concentration change. The projection result shows that the future summer morality in South Korea is increased due to changes in both temperature and ozone, and the magnitude of ozone-related increase is much smaller than that of temperature-related increase, especially in the 2050s.

Temperature Characteristics of Porous Portland Cement Concrete during the Hot Summer Session

Directory of Open Access Journals (Sweden)

Liqun Hu

2017-01-01

Full Text Available Pavement heats the near-surface air and affects the thermal comfort of the human body in hot summer. Because of a large amount of connected porosity of porous Portland cement concrete (PPCC, the thermal parameters of PPCC are much different from those of traditional Portland cement concrete (PCC. The temperature change characteristics of PPCC and the effects on surrounding environment are also different. A continuous 48-hour log of temperature of a PCC and five kinds of PPCC with different porosity were recorded in the open air in the hot summer. The air temperatures at different heights above concrete specimens were tested using self-made enclosed boxes to analyze the characteristics of near-surface air temperature. The output heat flux of different concrete specimens was calculated. The results show that the PPCC has higher temperature in the daytime and lower temperature in the nighttime and larger temperature gradient than the PCC. The air temperature above PPCC is lower than that of PCC after solar radiation going to zero at night. The total output heat flux of PPCC is slightly smaller in the daytime and significantly smaller at night than that of PCC. The results of tests and calculations indicate that PPCC contributes to the mitigation of heating effect of pavement on the near-surface air.

Scale-dependency of the global mean surface temperature trend and its implication for the recent hiatus of global warming.

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Lin, Yong; Franzke, Christian L E

2015-08-11

Studies of the global mean surface temperature trend are typically conducted at a single (usually annual or decadal) time scale. The used scale does not necessarily correspond to the intrinsic scales of the natural temperature variability. This scale mismatch complicates the separation of externally forced temperature trends from natural temperature fluctuations. The hiatus of global warming since 1999 has been claimed to show that human activities play only a minor role in global warming. Most likely this claim is wrong due to the inadequate consideration of the scale-dependency in the global surface temperature (GST) evolution. Here we show that the variability and trend of the global mean surface temperature anomalies (GSTA) from January 1850 to December 2013, which incorporate both land and sea surface data, is scale-dependent and that the recent hiatus of global warming is mainly related to natural long-term oscillations. These results provide a possible explanation of the recent hiatus of global warming and suggest that the hiatus is only temporary.

Decadal Variation of the Relationship between Western Pacific Subtropical High and Summer Heatwaves in East China Modulated by Pacific Decadal Oscillation

Science.gov (United States)

Liu, Q.; Fu, C.; Zhou, T.

2017-12-01

This study investigates the relationship between Western Pacific Subtropical High (WPSH) and summer heatwaves over Eastern China in interannual scale during the period of 1959-2016. Based on surface daily maximum temperature of 654 monitoring stations over China and meteorological variables in reanalysis data, we calculate the number of heatwave days (NHD) (one heatwave day was defined as one day with its daily maximum temperature greater than 35 degrees centigrade) as well as WPSH index and then examine their interannual relationship. Although the high-NHD-related 850hPa horizontal wind structure was shared by that of high WPSH and decaying El Niño summer, a decadal oscillation emerges for the correlation between interannual WPSH and NHD after removing their interdecadal variability by Ensemble Empirical Mode Decomposition (EEMD) method. The correlation coefficient can reach up to as high as 0.69 and as low as 0.17 and assembles the Pacific Decadal Oscillation (PDO) pretty well. Compositing analysis demonstrates that unstable WPSH-NHD relationship is mainly attributed to the spatial structure distinction of WPSH and surface warming in the El Niño decaying summer of different PDO phases. In the El Niño decaying summer of positive PDO phases, remarkable enhanced warming over majority of Southeastern China matches well with the noticeable westward extension of WPSH, which seems to be forced by the cyclonic circulation anomaly over Japan. The warmer Pacific-Indian Ocean Warm Pool intensifies the Matsuno-Gill pattern over Maritime Continent, stimulating this cyclonic circulation anomaly via the northward propagation of Rossby wave. In the El Niño decaying summer of negative PDO phases, the cooler East China Sea enhances WPSH in North China and South China Sea, and thereby leads to a local cyclonic circulation anomaly over Eastern China, which would cause a large scope of cooling and out-of-phase WPSH-NHD relationship.

Potential forcings of summer temperature variability of the southeastern Tibetan Plateau in the past 12 ka

Science.gov (United States)

Zhang, Enlou; Chang, Jie; Sun, Weiwei; Cao, Yanmin; Langdon, Peter; Cheng, Jun

2018-06-01

Investigating potential forcing mechanisms of terrestrial summer temperature changes from the Asian summer monsoon influenced area is of importance to better understand the climate variability in these densely populated regions. The results of spectral and wavelet analyses of the published chironomid reconstructed mean July temperature data from Tiancai Lake on the SE Tibetan Plateau are presented. The evidence of solar forcing of the summer temperature variability from the site on centennial timescales where key solar periodicities (at 855 ± 40, 465 ± 40, 315 ± 40 and 165 ± 40 year) are revealed. By using a band-pass filter, coherent fluctuations were found in the strength of Asian summer monsoon, Northern Hemisphere high latitude climate and high elevation mid-latitude (26°N) terrestrial temperatures with solar sunspot cycles since about 7.6 ka. The two abrupt cooling events detected from the Tiancai Lake record, centered at ∼9.7 and 3.5 ka were examined respectively. Coupled with the paleoclimate modeling results, the early Holocene event (9.7 ka) is possibly linked to an ocean-atmospheric feedback mechanism whereas the latter event (3.5 ka) may be more directly related to external forcing.

Phylogeographic differentiation versus transcriptomic adaptation to warm temperatures in Zostera marina, a globally important seagrass.

Science.gov (United States)

Jueterbock, A; Franssen, S U; Bergmann, N; Gu, J; Coyer, J A; Reusch, T B H; Bornberg-Bauer, E; Olsen, J L

2016-11-01

Populations distributed across a broad thermal cline are instrumental in addressing adaptation to increasing temperatures under global warming. Using a space-for-time substitution design, we tested for parallel adaptation to warm temperatures along two independent thermal clines in Zostera marina, the most widely distributed seagrass in the temperate Northern Hemisphere. A North-South pair of populations was sampled along the European and North American coasts and exposed to a simulated heatwave in a common-garden mesocosm. Transcriptomic responses under control, heat stress and recovery were recorded in 99 RNAseq libraries with ~13 000 uniquely annotated, expressed genes. We corrected for phylogenetic differentiation among populations to discriminate neutral from adaptive differentiation. The two southern populations recovered faster from heat stress and showed parallel transcriptomic differentiation, as compared with northern populations. Among 2389 differentially expressed genes, 21 exceeded neutral expectations and were likely involved in parallel adaptation to warm temperatures. However, the strongest differentiation following phylogenetic correction was between the three Atlantic populations and the Mediterranean population with 128 of 4711 differentially expressed genes exceeding neutral expectations. Although adaptation to warm temperatures is expected to reduce sensitivity to heatwaves, the continued resistance of seagrass to further anthropogenic stresses may be impaired by heat-induced downregulation of genes related to photosynthesis, pathogen defence and stress tolerance. © 2016 John Wiley & Sons Ltd.

Impacts of the leading modes of tropical Indian Ocean sea surface temperature anomaly on sub-seasonal evolution of the circulation and rainfall over East Asia during boreal spring and summer

Science.gov (United States)

Liu, Senfeng; Duan, Anmin

2017-02-01

The two leading modes of the interannual variability of the tropical Indian Ocean (TIO) sea surface temperature (SST) anomaly are the Indian Ocean basin mode (IOBM) and the Indian Ocean dipole mode (IODM) from March to August. In this paper, the relationship between the TIO SST anomaly and the sub-seasonal evolution of the circulation and rainfall over East Asia during boreal spring and summer is investigated by using correlation analysis and composite analysis based on multi-source observation data from 1979 to 2013, together with numerical simulations from an atmospheric general circulation model. The results indicate that the impacts of the IOBM on the circulation and rainfall over East Asia vary remarkably from spring to summer. The anomalous anticyclone over the tropical Northwest Pacific induced by the warm IOBM is closely linked with the Pacific-Japan or East Asia-Pacific teleconnection pattern, which persists from March to August. In the upper troposphere over East Asia, the warm phase of the IOBM generates a significant anticyclonic response from March to May. In June and July, however, the circulation response is characterized by enhanced subtropical westerly flow. A distinct anomalous cyclone is found in August. Overall, the IOBM can exert significant influence on the western North Pacific subtropical high, the South Asian high, and the East Asian jet, which collectively modulate the precipitation anomaly over East Asia. In contrast, the effects of the IODM on the climate anomaly over East Asia are relatively weak in boreal spring and summer. Therefore, studying the impacts of the TIO SST anomaly on the climate anomaly in East Asia should take full account of the different sub-seasonal response during boreal spring and summer.

Estimating thermal regimes of bull trout and assessing the potential effects of climate warming on critical habitats

Science.gov (United States)

Jones, Leslie A.; Muhlfeld, Clint C.; Marshall, Lucy A.; McGlynn, Brian L.; Kershner, Jeffrey L.

2013-01-01

Understanding the vulnerability of aquatic species and habitats under climate change is critical for conservation and management of freshwater systems. Climate warming is predicted to increase water temperatures in freshwater ecosystems worldwide, yet few studies have developed spatially explicit modelling tools for understanding the potential impacts. We parameterized a nonspatial model, a spatial flow-routed model, and a spatial hierarchical model to predict August stream temperatures (22-m resolution) throughout the Flathead River Basin, USA and Canada. Model comparisons showed that the spatial models performed significantly better than the nonspatial model, explaining the spatial autocorrelation found between sites. The spatial hierarchical model explained 82% of the variation in summer mean (August) stream temperatures and was used to estimate thermal regimes for threatened bull trout (Salvelinus confluentus) habitats, one of the most thermally sensitive coldwater species in western North America. The model estimated summer thermal regimes of spawning and rearing habitats at <13 C° and foraging, migrating, and overwintering habitats at <14 C°. To illustrate the useful application of such a model, we simulated climate warming scenarios to quantify potential loss of critical habitats under forecasted climatic conditions. As air and water temperatures continue to increase, our model simulations show that lower portions of the Flathead River Basin drainage (foraging, migrating, and overwintering habitat) may become thermally unsuitable and headwater streams (spawning and rearing) may become isolated because of increasing thermal fragmentation during summer. Model results can be used to focus conservation and management efforts on populations of concern, by identifying critical habitats and assessing thermal changes at a local scale.

Cooling-water amounts, temperature, and the environment

International Nuclear Information System (INIS)

Koops, F.B.J.; Donze, M.; Hadderingh, R.H.

1979-01-01

The release of heat from power plants into a water can take place with relative small quantities of cooling water, highly warmed up accordingly, or with large quantities of cooling water slightly warmed up. The utilization of cooling water is bound to certain guidelines established by the authorities. With the intention to protect the environment, the admissable temperatures and warming-up have been strictly limited by the authorities. In the Netherlands, we have presently temporary cooling water guidelines which allow a max. temperature of the cooling water in the cooling cycle of 30 0 C and a maximum admissible temperature rise in the condenser between 7 0 C during summer and 15 0 C during winter. It has also been determined in these requirements how much cooling water at least has to be used to discharge a specified quantity of heat. Plankton, spawn and young fish are dragged with the cooling water. Harm to these organisms can be caused mechanically by pumps, sieves and the condenser or they can be harmed by the temperature rise in the condenser. Investigations showed that mechanical harm to spawn and young fish in the cooling water flow should not be ignored, and that detectable harm to plankton organisms takes place only at water temperatures above 32 0 C. The cooling water consumption can therefore be optimised as follows: The solution of a greater temperature increase and a slightly higher value for the temperature maximum can reduce the cooling water quantity. This reduction of the cooling water quantity reduces the destruction of the fish quantity, which gets into the cooling water system, especially during the summer. If the temperature rise and the temperature itself are not selected too high, the destruction of fish may be reduced without causing serious damage to the plankton. (orig.) [de

Summer declines in activity and body temperature offer polar bears limited energy savings

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Whiteman, J.P.; Harlow, H.J.; Durner, George M.; Anderson-Sprecher, R.; Albeke, Shannon E.; Regehr, Eric V.; Amstrup, Steven C.; Ben-David, M.

2015-01-01

Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of “ice” bears in summer is unknown, “shore” bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation.

TEMPERATURE AND PRECIPITATION CHANGES IN TÂRGU-MURES (ROMANIA FROM PERIOD 1951-2010

Directory of Open Access Journals (Sweden)

O.Rusz

2012-03-01

Full Text Available Temperature and precipitation changes in Târgu Mures (Romania from period 1951-2010. The analysis was made based upon meteorological data collected at Târgu Mures meteorological station (Romania, Mures county, lat. 46°32’N, lon. 24°32’E, elevation 308 m, between 1951 and 2010. Several climatic parameters were studied (for instance, annual and monthly mean temperature, maximum precipitation in 24 hours, number of summer days, etc. Detected inhomogeneities are not related to instrumental causes or geographical relocation. Positive and statistical significant trends (Mann-Kendall test are indicated for: mean annual temperatures, mean temperatures of warm months, average of the maximum and minimum temperatures (annual and warm months data, number of days with mean temperature between 20.1-25.0 °C, number of days with precipitation ≥0 mm, and for all parameters of precipitation of September. The sequential version of Mann-Kendall test show a beginning of a trend in 1956 in the case of mean temperature (at same, the two and three parts regression denote this year like a moment of change, years 1965 and 1992 in the case of annual amount of precipitation. CUSUM charts indicate occurs of changes points at 1988, 2005, 2009 (mean temperature respectively at 1989, 2004 (precipitation, and at 1968, 1992 (daily temperature range. Tendencies of overlapped time series reveal a more important increase at the end of period (mainly for mean temperature. The analysis with RClimDex show for 5 extreme climate indices a significant trend: positive for summer days, warm nights, warm spell duration indicator and negative for cold nights and cold days.

Three responses to small changes in stream temperature by autumn-emerging aquatic insects

Science.gov (United States)

Judith L. Li; Sherri L. Johnson; Janel Banks. Sobota

2011-01-01

In this experimental study, conducted in coastal Oregon USA, we examined how small increases in summer water temperatures affected aquatic insect growth and autumn emergence. We maintained naturally fluctuating temperatures from 2 nearby streams and a 3rd regime, naturally fluctuating temperatures warmed by 3-5°C, in flow-through troughs from mid...

Unusually amplified summer or winter indoor levels of radon

International Nuclear Information System (INIS)

Gammage, R.B.; Dudney, C.S.; Wilson, D.L.

1993-01-01

The ratios of winter/summer indoor radon levels for houses in different regions of the southern Appalachians are characterized by individual log-normal distributions with geometric means both above and below unity. In some counties and cities, subpopulations of houses have unusually exaggerated winter/summer ratios of indoor radon, as well as high indoor radon levels, during periods of either warm or cool weather. It is proposed that in many instances, houses are communicating with larger than normal underground reservoirs of radon-bearing air in hilly karst terrains; differences between the outdoor and underground air temperatures are believed to provide density gradients producing aerostatic pressure differences for seasonally directed underground transport and subsequently elevated indoor radon. These seasonal movements of air are analogous to the well-known underground chimney effects, which produce interzonal flows of air inside caves

Experimental climate warming decreases photosynthetic efficiency of lichens in an arid South African ecosystem.

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Maphangwa, Khumbudzo Walter; Musil, Charles F; Raitt, Lincoln; Zedda, Luciana

2012-05-01

Elevated temperatures and diminished precipitation amounts accompanying climate warming in arid ecosystems are expected to have adverse effects on the photosynthesis of lichen species sensitive to elevated temperature and/or water limitation. This premise was tested by artificially elevating temperatures (increase 2.1-3.8°C) and reducing the amounts of fog and dew precipitation (decrease 30.1-31.9%), in an approximation of future climate warming scenarios, using transparent hexagonal open-top warming chambers placed around natural populations of four lichen species (Xanthoparmelia austroafricana, X. hyporhytida , Xanthoparmelia. sp., Xanthomaculina hottentotta) at a dry inland site and two lichen species (Teloschistes capensis and Ramalina sp.) at a humid coastal site in the arid South African Succulent Karoo Biome. Effective photosynthetic quantum yields ([Formula: see text]) were measured hourly throughout the day at monthly intervals in pre-hydrated lichens present in the open-top warming chambers and in controls which comprised demarcated plots of equivalent open-top warming chamber dimensions constructed from 5-cm-diameter mesh steel fencing. The cumulative effects of the elevated temperatures and diminished precipitation amounts in the open-top warming chambers resulted in significant decreases in lichen [Formula: see text]. The decreases were more pronounced in lichens from the dry inland site (decline 34.1-46.1%) than in those from the humid coastal site (decline 11.3-13.7%), most frequent and prominent in lichens at both sites during the dry summer season, and generally of greatest magnitude at or after the solar noon in all seasons. Based on these results, we conclude that climate warming interacting with reduced precipitation will negatively affect carbon balances in endemic lichens by increasing desiccation damage and reducing photosynthetic activity time, leading to increased incidences of mortality.

Variability of East Asian summer monsoon precipitation during the Holocene and possible forcing mechanisms

Science.gov (United States)

Lu, Fuzhi; Ma, Chunmei; Zhu, Cheng; Lu, Huayu; Zhang, Xiaojian; Huang, Kangyou; Guo, Tianhong; Li, Kaifeng; Li, Lan; Li, Bing; Zhang, Wenqing

2018-03-01

Projecting how the East Asian summer monsoon (EASM) rainfall will change with global warming is essential for human sustainability. Reconstructing Holocene climate can provide critical insight into its forcing and future variability. However, quantitative reconstructions of Holocene summer precipitation are lacking for tropical and subtropical China, which is the core region of the EASM influence. Here we present high-resolution annual and summer rainfall reconstructions covering the whole Holocene based on the pollen record at Xinjie site from the lower Yangtze region. Summer rainfall was less seasonal and 30% higher than modern values at 10-6 cal kyr BP and gradually declined thereafter, which broadly followed the Northern Hemisphere summer insolation. Over the last two millennia, however, the summer rainfall has deviated from the downward trend of summer insolation. We argue that greenhouse gas forcing might have offset summer insolation forcing and contributed to the late Holocene rainfall anomaly, which is supported by the TraCE-21 ka transient simulation. Besides, tropical sea-surface temperatures could modulate summer rainfall by affecting evaporation of seawater. The rainfall pattern concurs with stalagmite and other proxy records from southern China but differs from mid-Holocene rainfall maximum recorded in arid/semiarid northern China. Summer rainfall in northern China was strongly suppressed by high-northern-latitude ice volume forcing during the early Holocene in spite of high summer insolation. In addition, the El Niño/Southern Oscillation might be responsible for droughts of northern China and floods of southern China during the late Holocene. Furthermore, quantitative rainfall reconstructions indicate that the Paleoclimate Modeling Intercomparison Project (PMIP) simulations underestimate the magnitude of Holocene precipitation changes. Our results highlight the spatial and temporal variability of the Holocene EASM precipitation and potential forcing

Inter-Hemispheric Coupling During Northern Polar Summer Periods of 2002-2010 using TIMED/SABER Measurements

Science.gov (United States)

Goldberg, Richard A.; Feofilov, A. G.; Pesnell, W. D.; Kutepov, A. A.

2012-01-01

It has been found that for more than one polar summer season between 2002-2010, the northern polar mesospheric region near and above about 80 km was warmer than normal. The strongest warming effect of this type was observed to occur during northern summer 2002. Theoretical studies have implied that these "anomalies" were preceded by unusual dynamical processes in the southern hemisphere. We have analyzed temperature distributions measured by the SABER limb scanning infrared radiometer aboard the NASA TIMED satellite between 2002-2010 at altitudes from 15 to 110 km and for latitudes between 83 S to 83 N. We describe the approach to trace the inter-hemispheric temperature correlations demonstrating the global features that were unique for the "anomalous" northern polar summers. From our analysis of SABER data from 2002-2010, the anomalous heating for the northern mesopause region during northern summer was accompanied by stratospheric heating in the equatorial region. In the winter hemisphere it is accompanied by heating in the lower stratosphere and mesopause region, and cooling in the stratopause region. Also, all the elements of the temperature anomaly structure appear to develop and fade away nearly simultaneously, thereby suggesting either a global influence or a rapid exchange.

Oligocene sea water temperatures offshore Wilkes Land (Antarctica) indicate warm and stable glacial-interglacial variation and show no 'late Oligocene warming'

Science.gov (United States)

Hartman, Julian; Bijl, Peter; Peterse, Francien; Schouten, Stefan; Salabarnada, Ariadna; Bohaty, Steven; Escutia, Carlota; Brinkhuis, Henk; Sangiorgi, Francesca

2017-04-01

At present, warming of the waters below the Antarctic ice shelves is a major contributor to the instability of the Antarctic cryosphere. In order to get insight into future melt behavior of the Antarctic ice sheet, it is important to look at past warm periods that can serve as an analogue for the future. The Oligocene ( 34-23 Ma) is a period within the range of CO2 concentrations predicted by the latest IPCC report for the coming century and is characterized by a very dynamic Antarctic ice sheet, as suggested by benthic δ18O records from ice-distal sites. We suspect that, like today, environmental changes in the Southern Ocean are in part responsible for this dynamicity. To gain more insight into this, we have reconstructed sea water temperatures (SWT) based on Thaumarchaeotal lipids (TEX86) for the Oligocene record obtained from the ice-proximal Site U1356 (Integrated Ocean Drilling Program), offshore Wilkes Land. Part of our record shows a strong coupling between the lithology and SWT, which we attribute to glacial-interglacial variation. Our data shows that both glacial and interglacial temperatures are relatively warm throughout the Oligocene: 14°C and 18°C respectively, which is consistent with previously published estimates based on UK'37 and clumped isotopes for the early Oligocene. Our SST records show only a minor decline between 30 and 24 Ma, and thus show no evidence for a 'late Oligocene warming' as was suggested based on benthic δ18O records from low latitudes. Instead, the discrepancy between our SST trend and the δ18O trend suggests that the late-Oligocene benthic δ18O decrease is likely related to a decline in ice volume. After 24 Ma, however, glacial-interglacial temperature variation appears to increase. In particular, some large temperature drops occur, one of which can be related to the Mi-1 event and a major expansion of the Antarctic ice sheet.

Scale-dependency of the global mean surface temperature trend and its implication for the recent hiatus of global warming

Science.gov (United States)

Lin, Yong; Franzke, Christian L. E.

2015-01-01

Studies of the global mean surface temperature trend are typically conducted at a single (usually annual or decadal) time scale. The used scale does not necessarily correspond to the intrinsic scales of the natural temperature variability. This scale mismatch complicates the separation of externally forced temperature trends from natural temperature fluctuations. The hiatus of global warming since 1999 has been claimed to show that human activities play only a minor role in global warming. Most likely this claim is wrong due to the inadequate consideration of the scale-dependency in the global surface temperature (GST) evolution. Here we show that the variability and trend of the global mean surface temperature anomalies (GSTA) from January 1850 to December 2013, which incorporate both land and sea surface data, is scale-dependent and that the recent hiatus of global warming is mainly related to natural long-term oscillations. These results provide a possible explanation of the recent hiatus of global warming and suggest that the hiatus is only temporary. PMID:26259555

Temperature Trends in the Polar Mesosphere between 2002-2007 using TIMED/SABER Data

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Goldberg, Richard A.; Kutepov, Alexander A.; Pesnell, William Dean; Latteck, Ralph; Russell, James M.

2008-01-01

The TIMED Satellite was launched on December 7, 2001 to study the dynamics and energy of the mesosphere and lower thermosphere. The TIMED/SABER instrument is a limb scanning infrared radiometer designed to measure a large number of minor constituents as well as the temperature of the region. In this study, we have concentrated on the polar mesosphere, to investigate the temperature characteristics as a function of spatial and temporal considerations. We used the recently revised SABER dataset (1.07) that contains improved temperature retrievals in the Earth polar summer regions. Weekly averages are used to make comparisons between the winter and summer, as well as to study the variability in different quadrants of each hemisphere. For each year studied, the duration of polar summer based on temperature measurements compares favorably with the PMSE (Polar Mesospheric Summer Echoes) season measured by radar at the ALOMAR Observatory in Norway (69 N). The PMSE period should also define the summer period suitable for the occurrence of polar mesospheric clouds. The unusual short and relatively warm polar summer in the northern hemisphere

Global warming: it's not only size that matters

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Hegerl, Gabriele C.

2011-09-01

impacts than temperatures that have occurred frequently due to internal climate variability. Determining when exactly temperatures enter unusual ranges may be done in many different ways (and the paper shows several, and more could be imagined), but the main result of first local emergence in low latitudes remains robust. A worrying factor is that the regions where the signal is expected to emerge first, or is already emerging are largely regions in Africa, parts of South and Central America, and the Maritime Continent; regions that are vulnerable to climate change for a variety of regions (see IPCC 2007), and regions which contribute generally little to global greenhouse gas emissions. In contrast, strong emissions of greenhouse gases occur in regions of low warming-to-variability ratio. To get even closer to the relevance of this finding for impacts, it would be interesting to place the emergence of highly unusual summer temperatures in the context not of internal variability, but in the context of variability experienced by the climate system prior to the 20th century, as, e.g. documented in palaeoclimatic reconstructions and simulated in simulations of the last millennium (see Jansen et al 2007). External forcing has moved the temperature range around more strongly for some regions and in some seasons than others. For example, while reconstructions of summer temperatures in Europe appear to show small long-term variations, winter shows deep drops in temperature in the little Ice Age and a long-term increase since then (Luterbacher et al 2004), which was at least partly caused by external forcing (Hegerl et al 2011a) and therefore 'natural variability' may be different from internal variability. A further interesting question in attempts to provide a climate-based proxy for impacts of climate change is: to what extent does the rapidity of change matter, and how does it compare to trends due to natural variability? It is reasonable to assume that fast changes impact

Slow coolant phaseout could worsen warming

Science.gov (United States)

Reese, April

2018-03-01

In the summer of 2016, temperatures in Phalodi, an old caravan town on a dry plain in northwestern India, reached a blistering 51°C—a record high during a heat wave that claimed more than 1600 lives across the country. Wider access to air conditioning (AC) could have prevented many deaths—but only 8% of India's 249 million households have AC. As the nation's economy booms, that figure could rise to 50% by 2050. And that presents a dilemma: As India expands access to a life-saving technology, it must comply with international mandates—the most recent imposed just last fall—to eliminate coolants that harm stratospheric ozone or warm the atmosphere.

Global Warming Threatens National Interests in the Arctic

Science.gov (United States)

2009-03-26

Global warming has impacted the Arctic Ocean by significantly reducing the extent of the summer ice cover allowing greater access to the region...increased operations in the Arctic region, and DoD must continue to research and develop new and alternate energy sources for its forces. Global warming is

Temperature responses of tropical to warm temperate Cladophora species in relation to their distribution in the North Atlantic Ocean

Science.gov (United States)

Cambridge, M. L.; Breeman, A. M.; Kraak, S.; van den Hoek, C.

1987-09-01

The relationship between distribution boundaries and temperature responses of some North Atlantic Cladophora species (Chlorophyta) was experimentally examined under various regimes of temperature, light and daylength. Experimentally determined critical temperature intervals, in which survival, growth or reproduction was limited, were compared with annual temperature regimes (monthly means and extremes) at sites inside and outside distribution boundaries. The species tested belonged to two phytogeographic groups: (1) the tropical West Atlantic group ( C. submarina: isolate from Curaçao) and (2) the amphiatlantic tropical to warm temperate group ( C. prolifera: isolate from Corsica; C. coelothrix: isolates from Brittany and Curaçao; and C. laetevirens: isolates from deep and shallow water in Corsica and from Brittany). In accordance with distribution from tropical to warm temperate regions, each of the species grew well between 20 30°C and reproduction and growth were limited at and below 15°C. The upper survival limit in long days was <35°C in all species but high or maximum growth rates occurred at 30°C. C. prolifera, restricted to the tropical margins, had the most limited survival at 35°C. Experimental evidence suggests that C. submarina is restricted to the Caribbean and excluded from the more northerly American mainland and Gulf of Mexico coasts by sporadic low winter temperatures in the nearshore waters, when cold northerly weather penetrates far south every few years. Experimental evidence suggests that C. prolifera, C. coelothrix and C. laetevirens are restricted to their northern European boundaries by summer temperatures too low for sufficient growth and/or reproduction. Their progressively more northerly located boundaries were accounted for by differences in growth rates over the critical 10 15°C interval. C. prolifera and C. coelothrix are excluded or restricted in distribution on North Sea coasts by lethal winter temperatures, again differences

Warming Trends and Bleaching Stress of the World’s Coral Reefs 1985–2012

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Heron, Scott F.; Maynard, Jeffrey A.; van Hooidonk, Ruben; Eakin, C. Mark

2016-01-01

Coral reefs across the world’s oceans are in the midst of the longest bleaching event on record (from 2014 to at least 2016). As many of the world’s reefs are remote, there is limited information on how past thermal conditions have influenced reef composition and current stress responses. Using satellite temperature data for 1985–2012, the analysis we present is the first to quantify, for global reef locations, spatial variations in warming trends, thermal stress events and temperature variability at reef-scale (~4 km). Among over 60,000 reef pixels globally, 97% show positive SST trends during the study period with 60% warming significantly. Annual trends exceeded summertime trends at most locations. This indicates that the period of summer-like temperatures has become longer through the record, with a corresponding shortening of the ‘winter’ reprieve from warm temperatures. The frequency of bleaching-level thermal stress increased three-fold between 1985–91 and 2006–12 – a trend climate model projections suggest will continue. The thermal history data products developed enable needed studies relating thermal history to bleaching resistance and community composition. Such analyses can help identify reefs more resilient to thermal stress. PMID:27922080

Extreme summer temperatures in Iberia: health impacts and associated synoptic conditions

OpenAIRE

Garcia-Herrera , R.; Diaz , J.; Trigo , R. M.; Hernández , E.

2005-01-01

This paper examines the effect of extreme summer temperatures on daily mortality in two large cities of Iberia: Lisbon (Portugal) and Madrid (Spain). Daily mortality and meteorological variables are analysed using the same methodology based on Box-Jenkins models. Results reveal that in both cases there is a triggering effect on mortality when maximum daily temperature exceeds a given threshold (34°C in Lisbon and 36°C in Madrid). The impact of most intense heat events is very ...

Impact of Environmental Changes and Global Warming on Temperature in Pakistan

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Ishtiaq Hassan

2011-01-01

Full Text Available Environmental changes and global warming have direct impact on human life. Estimation of these changes in various parameters of hydrologic cycle is necessary for future planning and development of a country. In this paper the impact of environmental changes and global warming on temperatures of Pakistan has been studied. The temperature changes in Pakistan have been extracted from simulations made using EdGCM model developed at Columbia University. Simulation study to the end of 21st century is executed using the model for GHG (Greenhouse Gases scenario with doubled_CO2 and scenario of Modern_Predicted SST (Sea Surface Temperature. The model analysis has been carried out for seasonal and annual changes for an average of last 5 years period from 2096-2100. Maps are generated to depict global temperature variations. The study divides Pakistan into five (05 main areas for twenty six (26 stations. A part-plan of globe focusing Pakistan is generated showing the five divisions for twenty six (26 data stations of Pakistan. This part plan is made compatible with grid-box resolution of EdGCM. Eagle-Point Engineering software has been used to generate isohyets of interval (0.5oC for downscaling GCM (Global Climate Model grid data to data stations. The station values of different seasons and annual changes are then compared with the values of base period data to determine changes in temperature. It is observed that impact of global environmental changes on temperature are higher (i.e. there is an increase in annual temperature for double_CO2 experiment at places near the Arabian Sea than areas located away from this sea. It is also observed that the temperature increase will be more in winter than that in other seasons for Pakistan.

Change in the relationship between the Australian summer monsoon circulation and boreal summer precipitation over Central China in the late 1990s

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Yang, Ruowen; Wang, Jian; Zhang, Tianyu; He, Shengping

2017-09-01

Recent study revealed a close connection between the Australian summer monsoon (ASM) and boreal summer precipitation over Central China (SPCC). This study further revealed a strengthening of the ASM-SPCC relationship around the late 1990s. It is found that the relationship between the ASM and the SPCC during 1979-1997 (1998-2014) relationship is statistically insignificant (significant). Further analysis indicated that during 1998-2014, the weakened ASM is concurrent with significant positive sea surface temperature (SST) in the Indian Ocean and South China Sea, which could persist into the following boreal summer and further lead to intensified East Asian summer monsoon, strengthened western North Pacific subtropical high, and anomalous ascending motion over Central China. Consequently, more moisture is transported from the western Pacific northward to Central China where significant anomalous convergence appears. Therefore, the ASM could potentially influence the SPCC during 1998-2014. By contrast, the ASM-related SST and atmospheric circulation anomalies in boreal winter are statistically insignificant during 1979-1997. Such an interdecadal change might be attributed to the interdecadal warming that occurred in the Indian Ocean and South China Sea around the late 1990s. This study might be useful for the prediction of the SPCC.

Striking Seasonality in the Secular Warming of the Northern Continents: Structure and Mechanisms

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Nigam, S.; Thomas, N. P.

2017-12-01

The linear trend in twentieth-century surface air temperature (SAT)—a key secular warming signal— exhibits striking seasonal variations over Northern Hemisphere continents; SAT trends are pronounced in winter and spring but notably weaker in summer and fall. The SAT trends in historical twentieth-century climate simulations informing the Intergovernmental Panel for Climate Change's Fifth Assessment show varied (and often unrealistic) strength and structure, and markedly weaker seasonal variation. The large intra-ensemble spread of winter SAT trends in some historical simulations was surprising, especially in the context of century-long linear trends, with implications for the detection of the secular warming signal. The striking seasonality of observed secular warming over northern continents warrants an explanation and the representation of related processes in climate models. Here, the seasonality of SAT trends over North America is shown to result from land surface-hydroclimate interactions and, to an extent, also from the secular change in low-level atmospheric circulation and related thermal advection. It is argued that the winter dormancy and summer vigor of the hydrologic cycle over middle- to high-latitude continents permit different responses to the additional incident radiative energy from increasing greenhouse gas concentrations. The seasonal cycle of climate, despite its monotony, provides an expanded phase space for the exposition of the dynamical and thermodynamical processes generating secular warming, and an exceptional cost-effective opportunity for benchmarking climate projection models.

Tree-ring temperature reconstructions for the northeastern United States from Chamaecyparis thyoides

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Anchukaitis, K. J.; Pederson, N.; Pearl, J. K.; Donnelly, J. P.

2014-12-01

Over the last century, the northeastern United States has warmed by over 1C, with the region of strongest warming found in coastal Massachusetts, Connecticut, and Rhode Island. These states are amongst the fastest warming in the entire country and the region as a whole is also warming faster than the national average. While these records all appear exceptional in the context of the last century, it is not known how these compare on longer time scales, to potential preindustrial late Holocene warm epochs, and in the context of decadal-scale variability in regional climate. Here, we develop a January through August temperature reconstruction using three Chamaecyparis thyoides (Atlantic White Cedar) chronologies in Massachusetts and Maine. The chronologies show a strong winter-spring-summer temperature signal representative of temperature variability from southern New York to northeastern Maine. The reconstruction is skillful and tracks upwards temperature trends since the early 19th century, reproducing decadal scale variability associated with warming from the 1920s through 1940s, cooling in the region from the 1940s until the 1960s, and warming since that time. No year since at least the middle of the 19th century is as warm as the Janaury through August temperatures seen in the exceptionally warm 2012. Recent modeling experiments simulate a range of decadal warming trends for the northeastern United States that is slightly higher than the reconstructed and instrumental trends. Atlantic White Cedar holds the potential to develop multicentury temperature reconstructions from this heavily-populated region.

Increasing occurrence of cold and warm extremes during the recent global warming slowdown.

Science.gov (United States)

Johnson, Nathaniel C; Xie, Shang-Ping; Kosaka, Yu; Li, Xichen

2018-04-30

The recent levelling of global mean temperatures after the late 1990s, the so-called global warming hiatus or slowdown, ignited a surge of scientific interest into natural global mean surface temperature variability, observed temperature biases, and climate communication, but many questions remain about how these findings relate to variations in more societally relevant temperature extremes. Here we show that both summertime warm and wintertime cold extreme occurrences increased over land during the so-called hiatus period, and that these increases occurred for distinct reasons. The increase in cold extremes is associated with an atmospheric circulation pattern resembling the warm Arctic-cold continents pattern, whereas the increase in warm extremes is tied to a pattern of sea surface temperatures resembling the Atlantic Multidecadal Oscillation. These findings indicate that large-scale factors responsible for the most societally relevant temperature variations over continents are distinct from those of global mean surface temperature.

Perioperative warming with a thermal gown prevents maternal temperature loss during elective cesarean section. A randomized clinical trial.

Science.gov (United States)

de Bernardis, Ricardo Caio Gracco; Siaulys, Monica Maria; Vieira, Joaquim Edson; Mathias, Lígia Andrade Silva Telles

2016-01-01

Decrease in body temperature is common during general and regional anesthesia. Forced-air warming intraoperative during cesarean section under spinal anesthesia seems not able to prevent it. The hypothesis considers that active warming before the intraoperative period avoids temperature loss during cesarean. Forty healthy pregnant patients undergoing elective cesarean section with spinal anesthesia received active warming from a thermal gown in the preoperative care unit 30min before spinal anesthesia and during surgery (Go, n=20), or no active warming at any time (Ct, n=20). After induction of spinal anesthesia, the thermal gown was replaced over the chest and upper limbs and maintained throughout study. Room temperature, hemoglobin saturation, heart rate, arterial pressure, and tympanic body temperature were registered 30min before (baseline) spinal anesthesia, right after it (time zero) and every 15min thereafter. There was no difference for temperature at baseline, but they were significant throughout the study (p<0.0001; repeated measure ANCOVA). Tympanic temperature baseline was 36.6±0.3°C, measured 36.5±0.3°C at time zero and reached 36.1±0.2°C for gown group, while control group had baseline temperature of 36.4±0.4°C, measured 36.3±0.3°C at time zero and reached 35.4±0.4°C (F=32.53; 95% CI 0.45-0.86; p<0.001). Hemodynamics did not differ throughout the study for both groups of patients. Active warming 30min before spinal anesthesia and during surgery prevented a fall in body temperature in full-term pregnant women during elective cesarean delivery. Copyright © 2015 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

[Perioperative warming with a thermal gown prevents maternal temperature loss during elective cesarean section. A randomized clinical trial].

Science.gov (United States)

Bernardis, Ricardo Caio Gracco de; Siaulys, Monica Maria; Vieira, Joaquim Edson; Mathias, Lígia Andrade Silva Telles

2016-01-01

Decrease in body temperature is common during general and regional anesthesia. Forced-air warming intraoperative during cesarean section under spinal anesthesia seems not able to prevent it. The hypothesis considers that active warming before the intraoperative period avoids temperature loss during cesarean. Forty healthy pregnant patients undergoing elective cesarean section with spinal anesthesia received active warming from a thermal gown in the preoperative care unit 30min before spinal anesthesia and during surgery (Go, n=20), or no active warming at any time (Ct, n=20). After induction of spinal anesthesia, the thermal gown was replaced over the chest and upper limbs and maintained throughout study. Room temperature, hemoglobin saturation, heart rate, arterial pressure, and tympanic body temperature were registered 30min before (baseline) spinal anesthesia, right after it (time zero) and every 15min thereafter. There was no difference for temperature at baseline, but they were significant throughout the study (p<0.0001; repeated measure ANCOVA). Tympanic temperature baseline was 36.6±0.3°C, measured 36.5±0.3°C at time zero and reached 36.1±0.2°C for gown group, while control group had baseline temperature of 36.4±0.4°C, measured 36.3±0.3°C at time zero and reached 35.4±0.4°C (F=32.53; 95% CI 0.45-0.86; p<0.001). Hemodynamics did not differ throughout the study for both groups of patients. Active warming 30min before spinal anesthesia and during surgery prevented a fall in body temperature in full-term pregnant women during elective cesarean delivery. Copyright © 2015 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

Disentangling Global Warming, Multidecadal Variability, and El Niño in Pacific Temperatures

Science.gov (United States)

Wills, Robert C.; Schneider, Tapio; Wallace, John M.; Battisti, David S.; Hartmann, Dennis L.

2018-03-01

A key challenge in climate science is to separate observed temperature changes into components due to internal variability and responses to external forcing. Extended integrations of forced and unforced climate models are often used for this purpose. Here we demonstrate a novel method to separate modes of internal variability from global warming based on differences in time scale and spatial pattern, without relying on climate models. We identify uncorrelated components of Pacific sea surface temperature variability due to global warming, the Pacific Decadal Oscillation (PDO), and the El Niño-Southern Oscillation (ENSO). Our results give statistical representations of PDO and ENSO that are consistent with their being separate processes, operating on different time scales, but are otherwise consistent with canonical definitions. We isolate the multidecadal variability of the PDO and find that it is confined to midlatitudes; tropical sea surface temperatures and their teleconnections mix in higher-frequency variability. This implies that midlatitude PDO anomalies are more persistent than previously thought.

Differential effects of ambient temperature on warm cell responses to infrared radiation in the bloodsucking bug Rhodnius prolixus.

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Zopf, Lydia M; Lazzari, Claudio R; Tichy, Harald

2014-03-01

Thermoreceptors provide animals with background information about the thermal environment, which is at least indirectly a prerequisite for thermoregulation and assists bloodsucking insects in the search for their host. Recordings from peg-in-pit sensilla and tapered hairs on the antennae of the bug Rhodnius prolixus revealed two physiologically different types of warm cells. Both types responded more strongly to temperature pulses produced by switching between two air streams at different constant temperatures than to infrared radiation pulses employed in still air. In addition, both warm cells were better able to discriminate small changes in air temperature than in infrared radiation. As convective and radiant heat determines the discharge, it is impossible for a single warm cell to signal the nature of the stimulus unequivocally. Individual responses are ambiguous, not with regard to temperature change, but with regard to its source. We argue that the bugs use mechanical flow information to differentiate between pulses of convective and radiant heat. However, if pulses of radiant heat occur together with a constant temperature air stream, the mechanical cues would not allow avoiding ambiguity that convective heat introduces into radiant heat stimulation. In this situation, the warm cell in the tapered hairs produced stronger responses than those in the peg-in-pit sensilla. The reversal in the excitability of the two types of warm cells provides a criterion by which to distinguish the combination of convective and radiant heat from the stimuli presented alone.

Daily temperature changes and variability in ENSEMBLES regional models predictions: Evaluation and intercomparison for the Ebro Valley (NE Iberia)

KAUST Repository

El Kenawy, Ahmed M.

2014-12-18

We employ a suite of regional climate models (RCMs) to assess future changes in summer (JJA) maximum temperature (Tmax) over the Ebro basin, the largest hydrological division in the Iberian Peninsula. Under the A1B emission scenario, future changes in both mean values and their corresponding time varying percentiles were examined by comparing the control period (1971-2000) with two future time slices: 2021-2050 and 2071-2100. Here, the rationale is to assess how lower/upper tails of temperature distributions will change in the future and whether these changes will be consistent with those of the mean. The model validation results demonstrate significant differences among the models in terms of their capability to representing the statistical characteristics (e.g., mean, skewness and asymmetry) of the observed climate. The results also indicate that the current substantial warming observed in the Ebro basin is expected to continue during the 21st century, with more intense warming occurring at higher altitudes and in areas with greater distance from coastlines. All models suggest that the region will experience significant positive changes in both the cold and warm tails of temperature distributions. However, the results emphasize that future changes in the lower and upper tails of the summer Tmax distribution may not follow the same warming rate as the mean condition. In particular, the projected changes in the warm tail of the summer Tmax are shown to be significantly larger than changes in both mean values and the cold tail, especially at the end of the 21st century. The finding suggests that much of the changes in the summer Tmax percentiles will be driven by a shift in the entire distribution of temperature rather than only changes in the central tendency. Better understanding of the possible implications of future climate systems provides information useful for vulnerability assessments and the development of local adaptation strategies for multi

Effect of summer heat environment on body temperature, estrous cycles and blood antioxidant levels in Japanese Black cow.

Science.gov (United States)

Sakatani, Miki; Balboula, Ahmed Z; Yamanaka, Kenichi; Takahashi, Masashi

2012-05-01

This study investigated the effect of summer heat environment on estrous cycles and blood antioxidant levels in Japanese Black cows. A total of 13 non-lactating Japanese Black cows (summer: 9, winter: 4) were examined. Body temperature was measured rectally and intravaginally using a thermometer and data logger, respectively. Estrous behavior was monitored using a radiotelemetric pedometer that recorded walking activity. Rectal temperatures were higher during summer than winter (Pstress, and also reduces signs of estrus in Japanese Black cows. © 2011 The Authors. Animal Science Journal © 2011 Japanese Society of Animal Science.

Explaining the mechanisms through which regional atmospheric circulation variability drives summer temperatures and glacial melt in western High Mountain Asia (HMA)

Science.gov (United States)

Forsythe, Nathan; Fowler, Hayley; Blenkinsop, Stephen; Li, Xiaofeng; Pritchard, David

2017-04-01

Comprehension of mechanisms by which atmospheric circulation influences sub-regional temperature and water resources variability in high-elevation mountainous catchments is of great scientific urgency due to the dependency of large downstream populations on the river flows these basins provide. In this work we quantify a regional atmospheric pattern, the Karakoram Zonal Shear (KZS), with a very pronounced annual cycle which we standardise into a dimensionless (seasonal) circulation metric the Karakoram Zonal Index (KZI). Going beyond previous regional circulation metrics such as the "middle-upper tropospheric temperature index" (MUTTI) or the Webster and Yang Monsoonal Index (WYMI) which have focused solely on the South Asian Summer Monsoon (June to September) season, the KZS/KZI provides an indicator which captures the influence and interactions of the westerly jet throughout the entire annual cycle. Use of the KZS and KZI have led us to identify a further regional atmospheric system, the Karakoram Vortex, which propagates "warm high" (anticyclonic postitive temperature anomaly) and "cold low" (cyclonic negative temperature anomaly) patterns across a very broad swath of Central and South Asia in winter but over a much more constrained area of western HMA in summer. The KV exerts this temperature influence through a combination of adiabatic effects and large-scale advection. Quantify KV influence, the KZI shows strong and statistically significantly near surface (2m) air temperatures both across western HMA both as observed through local meteorological stations and as estimated by an ensemble of global meteorological reanalyses. We show that this strong influence on temperature translates to important consequences for meltwater generation from highly glaciated Indus river tributaries which is logical given that previous studies have established the role of air temperature in modulating glacially-derived river flows in western HMA. By improving the understanding of

The warming trend of ground surface temperature in the Choshui Alluvial Fan, western central Taiwan

Science.gov (United States)

Chen, W.; Chang, M.; Chen, J.; Lu, W.; Huang, C. C.; Wang, Y.

2013-12-01

Heat storage in subsurface of the continents forms a fundamental component of the global energy budget and plays an important role in the climate system. Several researches revealed that subsurface temperatures were being increased to 1.8-2.8°C higher in mean ground surface temperature (GST) for some Asian cities where are experiencing a rapid growth of population. Taiwan is a subtropic-tropic island with densely populated in the coastal plains surrounding its mountains. We investigate the subsurface temperature distribution and the borehole temperature-depth profiles by using groundwater monitoring wells in years 2000 and 2010. Our data show that the western central Taiwan plain also has been experiencing a warming trend but with a higher temperatures approximately 3-4 °C of GST during the last 250 yrs. We suggest that the warming were mostly due to the land change to urbanization and agriculture. The current GSTs from our wells are approximately 25.51-26.79 °C which are higher than the current surface air temperature (SAT) of 23.65 °C. Data from Taiwan's weather stations also show 1-1.5 °C higher for the GST than the SAT at neighboring stations. The earth surface heat balance data indicate that GST higher than SAT is reasonable. More researches are needed to evaluate the interaction of GST and SAT, and how a warming GST's impact to the SAT and the climate system of the Earth.

Response of a Habitat-Forming Marine Plant to a Simulated Warming Event Is Delayed, Genotype Specific, and Varies with Phenology.

Directory of Open Access Journals (Sweden)

Laura K Reynolds

Full Text Available Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of warming events increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate warming event of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass. We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14-15°C, but extended warming periods of 17-18°C occur episodically. Experimental warming increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of warming on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been warmed. While all genotypes' production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control were the most susceptible to the detrimental effects of warming. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species' thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient

Epipodial Tentacle Gene Expression and Predetermined Resilience to Summer Mortality in the Commercially Important Greenlip Abalone, Haliotis laevigata.

Science.gov (United States)

Shiel, Brett P; Hall, Nathan E; Cooke, Ira R; Robinson, Nicholas A; Strugnell, Jan M

2017-04-01

"Summer mortality" is a phenomenon that occurs during warm water temperature spikes that results in the mass mortality of many ecologically and economically important mollusks such as abalone. This study aimed to determine whether the baseline gene expression of abalone before a laboratory-induced summer mortality event was associated with resilience to summer mortality. Tentacle transcriptomes of 35 greenlip abalone (Haliotis laevigata) were sequenced prior to the animals being exposed to an increase in water temperature-simulating conditions which have previously resulted in summer mortality. Abalone derived from three source locations with different environmental conditions were categorized as susceptible or resistant to summer mortality depending on whether they died or survived after the water temperature was increased. We detected two genes showing significantly higher expression in resilient abalone relative to susceptible abalone prior to the laboratory-induced summer mortality event. One of these genes was annotated through the NCBI non-redundant protein database using BLASTX to an anemone (Exaiptasia pallida) Transposon Ty3-G Gag Pol polyprotein. Distinct gene expression signatures were also found between resilient and susceptible abalone depending on the population origin, which may suggest divergence in local adaptation mechanisms for resilience. Many of these genes have been suggested to be involved in antioxidant and immune-related functions. The identification of these genes and their functional roles have enhanced our understanding of processes that may contribute to summer mortality in abalone. Our study supports the hypothesis that prestress gene expression signatures are indicative of the likelihood of summer mortality.

How East Asian westerly jet's meridional position affects the summer rainfall in Yangtze-Huaihe River Valley?

Science.gov (United States)

Wang, Shixin; Zuo, Hongchao; Zhao, Shuman; Zhang, Jiankai; Lu, Sha

2017-03-01

Existing studies show that the change in the meridional position of East Asian westerly jet (EAWJ) is associated with rainfall anomalies in Yangtze-Huaihe River Valley (YHRV) in summer. However, the dynamic mechanism has not been resolved yet. The present study reveals underlying mechanisms for this impact for early summer and midsummer, separately. Mechanism1: associated with EAWJ's anomalously southward displacement, the 500-hPa westerly wind over YHRV is strengthened through midtropospheric horizontal circulation anomalies; the westerly anomalies are related to the formation of warm advection anomalies over YHRV, which cause increased rainfall through adiabatic ascent motion and convective activities; the major difference in these processes between early summer and midsummer is the midtropospheric circulation anomaly pattern. Mechanism 2: associated with EAWJ's anomalously southward displacement, the large day-to-day variability of midtropospheric temperature advection in midlatitudes is displaced southward by the jet's trapping transient eddies; this change enhances the day-to-day variability of temperature advection over YHRV, which in turn causes the increased rainfall in most part of YHRV through "lower-bound effect" (rainfall amount can not become negative); there is not much difference in these processes between early summer and midsummer.

Physical mechanisms of spring and summertime drought related with the global warming over the northern America

Science.gov (United States)

Choi, W.; Kim, K. Y.

2017-12-01

Drought during the growing season (spring through summer) is severe natural hazard in the large cropland over the northern America. It is important to understand how the drought is related with the global warming and how it will change in the future. This study aims to investigate the physical mechanism of global warming impact on the spring and summertime drought over the northern America using Cyclostationary Empirical Orthogonal Function (CSEOF) analysis. The Northern Hemisphere surface warming, the most dominant mode of the surface air temperature, has resulted in decreased relative humidity and precipitation over the mid-latitude region of North America. For the viewpoint of atmospheric water demand, soil moisture and evaporation have also decreased significantly, exacerbating vulnerability of drought. These consistent features of changes in water demand and supply related with the global warming can provide a possibility of credible insight for future drought change.

Impact of postglacial warming on borehole reconstructions of last millennium temperatures

Directory of Open Access Journals (Sweden)

V. Rath

2012-06-01

Full Text Available The investigation of observed borehole temperatures has proved to be a valuable tool for the reconstruction of ground surface temperature histories. However, there are still many open questions concerning the significance and accuracy of the reconstructions from these data. In particular, the temperature signal of the warming after the Last Glacial Maximum is still present in borehole temperature profiles. It is shown here that this signal also influences the relatively shallow boreholes used in current paleoclimate inversions to estimate temperature changes in the last centuries by producing errors in the determination of the steady state geothermal gradient. However, the impact on estimates of past temperature changes is weaker. For deeper boreholes, the curvature of the long-term signal is significant. A correction based on simple assumptions about glacial–interglacial temperature changes shows promising results, improving the extraction of millennial scale signals. The same procedure may help when comparing observed borehole temperature profiles with the results from numerical climate models.

Global warming: Sea ice and snow cover

International Nuclear Information System (INIS)

Walsh, J.E.

1993-01-01

In spite of differences among global climate simulations under scenarios where atmospheric CO 2 is doubled, all models indicate at least some amplification of greenouse warming at the polar regions. Several decades of recent data on air temperature, sea ice, and snow cover of the high latitudes of the Northern Hemisphere are summarized to illustrate the general compatibility of recent variations in those parameters. Despite a data void over the Arctic Ocean, some noteworthy patterns emerge. Warming dominates in winter and spring, as projected by global climate models, with the warming strongest over subpolar land areas of Alaska, northwestern Canada, and northern Eurasia. A time-longitude summary of Arctic sea ice variations indicates that timescales of most anomalies range from several months to several years. Wintertime maxima of total sea ice extent contain no apparent secular trends. The statistical significance of trends in recent sea ice variations was evaluated by a Monte Carlo procedure, showing a statistically significant negative trend in the summer. Snow cover data over the 20-y period of record show a noticeable decrease of Arctic snow cover in the late 1980s. This is of potential climatic significance since the accompanying decrease of surface albedo leads to a rapid increase of solar heating. 21 refs., 3 figs., 1 tab

Transient regional climate change: analysis of the summer climate response in a high-resolution, century-scale, ensemble experiment over the continental United States

Science.gov (United States)

Diffenbaugh, Noah S.; Ashfaq, Moetasim; Scherer, Martin

2013-01-01

Integrating the potential for climate change impacts into policy and planning decisions requires quantification of the emergence of sub-regional climate changes that could occur in response to transient changes in global radiative forcing. Here we report results from a high-resolution, century-scale, ensemble simulation of climate in the United States, forced by atmospheric constituent concentrations from the Special Report on Emissions Scenarios (SRES) A1B scenario. We find that 21st century summer warming permanently emerges beyond the baseline decadal-scale variability prior to 2020 over most areas of the continental U.S. Permanent emergence beyond the baseline annual-scale variability shows much greater spatial heterogeneity, with emergence occurring prior to 2030 over areas of the southwestern U.S., but not prior to the end of the 21st century over much of the southcentral and southeastern U.S. The pattern of emergence of robust summer warming contrasts with the pattern of summer warming magnitude, which is greatest over the central U.S. and smallest over the western U.S. In addition to stronger warming, the central U.S. also exhibits stronger coupling of changes in surface air temperature, precipitation, and moisture and energy fluxes, along with changes in atmospheric circulation towards increased anticylonic anomalies in the mid-troposphere and a poleward shift in the mid-latitude jet aloft. However, as a fraction of the baseline variability, the transient warming over the central U.S. is smaller than the warming over the southwestern or northeastern U.S., delaying the emergence of the warming signal over the central U.S. Our comparisons with observations and the Coupled Model Intercomparison Project Phase 3 (CMIP3) ensemble of global climate model experiments suggest that near-term global warming is likely to cause robust sub-regional-scale warming over areas that exhibit relatively little baseline variability. In contrast, where there is greater

Chironomid-based reconstructions of summer air temperature from lake deposits in Lyndon Stream, New Zealand spanning the MIS 3/2 transition

Science.gov (United States)

Woodward, C. A.; Shulmeister, J.

2007-01-01

We present chironomid-based temperature reconstructions from lake sediments deposited between ca 26,600 cal yr BP and 24,500 cal yr BP from Lyndon Stream, South Island, New Zealand. Summer (February mean) temperatures averaged 1 °C cooler, with a maximum inferred cooling of 3.7 °C. These estimates corroborate macrofossil and beetle-based temperature inferences from the same site and suggest climate amelioration (an interstadial) at this time. Other records from the New Zealand region also show a large degree of variability during the late Otiran glacial sequence (34,000-18,000 cal yr BP) including a phase of warming at the MIS 2/3 transition and a maximum cooling that did not occur until the global LGM (ca 20,000 cal yr BP). The very moderate cooling identified here at the MIS 2/3 transition confirms and enhances the long-standing discrepancy in New Zealand records between pollen and other proxies. Low abundances (<20%) of canopy tree pollen in records from late MIS 3 to the end of MIS 2 cannot be explained by the minor (<5 °C) cooling inferred from this and other studies unless other environmental parameters are considered. Further work is required to address this critical issue.

A dipole pattern in the Indian and Pacific oceans and its relationship with the East Asian summer monsoon

International Nuclear Information System (INIS)

Zheng, Jiayu; Feng, Juan; Li, Jianping

2014-01-01

This study demonstrates a robust relationship between the Indo-Pacific warm pool (IPWP) and North Pacific Ocean dipole (IPOD) and the East Asian summer monsoon (EASM) using observational datasets and sensitivity tests from the Community Atmosphere Model version 3.1 of the National Center for Atmospheric Research. The IPOD, which is a significant pattern of boreal summer SSTA in the Indian and Pacific oceans characterized by positive (negative) sea-surface temperature anomalies (SSTA) in the North Pacific and negative (positive) SSTA in the IPWP, appears around May, intensifies in the following months, and weakens in September. In summers with a positive IPOD phase, the western Pacific subtropical high (WPSH) weakens and shrinks with the axis of the WPSH ridge moving northwards, which favours an intensified EASM and a decrease in summer rainfall in the Yangtze River valley, and vice versa. (letter)

Effects of experimental warming and nitrogen addition on soil respiration and CH4 fluxes from crop rotations of winter wheat–soybean/fallow

DEFF Research Database (Denmark)

Liu, L; Hu, C; Yang, P

2015-01-01

Soil respiration and CH4 emissions play a significant role in the global carbon balance. However, in situ studies in agricultural soils on responses of soil respiration and CH4 fluxes to climate warming are still sparse, especially from long-term studies with year-round heating. A warming...... by affecting soil NH4 concentration. Across years, CH4 emissions were negatively correlated with soil temperature in N1 treatment. Soil respiration showed clear seasonal fluctuations, with the largest emissions during summer and smallest in winter. Warming and nitrogen fertilization had no significant effects...... on total cumulative soil CO2 fluxes. Soil respiration was positively correlated with microbial biomass C, and microbial biomass C was not affected significantly by warming or nitrogen addition. The lack of significant effects of warming on soil respiration may have resulted from: (1) warming-induced soil...

Drier summers cancel out the CO2 uptake enhancement induced by warmer springs.

Science.gov (United States)

Angert, A; Biraud, S; Bonfils, C; Henning, C C; Buermann, W; Pinzon, J; Tucker, C J; Fung, I

2005-08-02

An increase in photosynthetic activity of the northern hemisphere terrestrial vegetation, as derived from satellite observations, has been reported in previous studies. The amplitude of the seasonal cycle of the annually detrended atmospheric CO(2) in the northern hemisphere (an indicator of biospheric activity) also increased during that period. We found, by analyzing the annually detrended CO(2) record by season, that early summer (June) CO(2) concentrations indeed decreased from 1985 to 1991, and they have continued to decrease from 1994 up to 2002. This decrease indicates accelerating springtime net CO(2) uptake. However, the CO(2) minimum concentration in late summer (an indicator of net growing-season uptake) showed no positive trend since 1994, indicating that lower net CO(2) uptake during summer cancelled out the enhanced uptake during spring. Using a recent satellite normalized difference vegetation index data set and climate data, we show that this lower summer uptake is probably the result of hotter and drier summers in both mid and high latitudes, demonstrating that a warming climate does not necessarily lead to higher CO(2) growing-season uptake, even in high-latitude ecosystems that are considered to be temperature limited.

Global warming enhances sulphide stress in a key seagrass species (NW Mediterranean).

Science.gov (United States)

García, Rosa; Holmer, Marianne; Duarte, Carlos M; Marbà, Núria

2013-12-01

The build-up of sulphide concentrations in sediments, resulting from high inputs of organic matter and the mineralization through sulphate reduction, can be lethal to the benthos. Sulphate reduction is temperature dependent, thus global warming may contribute to even higher sulphide concentrations and benthos mortality. The seagrass Posidonia oceanica is very sensitive to sulphide stress. Hence, if concentrations build up with global warming, this key Mediterranean species could be seriously endangered. An 8-year monitoring of daily seawater temperature, the sulphur isotopic signatures of water (δ(34)S(water)), sediment (δ(34)SCRS ) and P. oceanica leaf tissue (δ(34)S(leaves)), along with total sulphur in leaves (TS(leaves)) and annual net population growth along the coast of the Balearic archipelago (Western Mediterranean) allowed us to determine if warming triggers P. oceanica sulphide stress and constrains seagrass survival. From the isotopic S signatures, we estimated sulphide intrusion into the leaves (F(sulphide)) and sulphur incorporation into the leaves from sedimentary sulphides (SS(leaves)). We observed lower δ(34)S(leaves), higher F(sulphide) and SS(leaves) coinciding with a 6-year period when two heat waves were recorded. Warming triggered sulphide stress as evidenced by the negative temperature dependence of δ(34)S(leaves) and the positive one of F(sulphide), TS(leaves) and SS(leaves). Lower P. oceanica net population growth rates were directly related to higher contents of TS(leaves). At equivalent annual maximum sea surface water temperature (SST(max)), deep meadows were less affected by sulphide intrusion than shallow ones. Thus, water depth acts as a protecting mechanism against sulphide intrusion. However, water depth would be insufficient to buffer seagrass sulphide stress triggered by Mediterranean seawater summer temperatures projected for the end of the 21st century even under scenarios of moderate greenhouse gas emissions, A1B

Understanding the tropical warm temperature bias simulated by climate models

Science.gov (United States)

Brient, Florent; Schneider, Tapio

2017-04-01

The state-of-the-art coupled general circulation models have difficulties in representing the observed spatial pattern of surface tempertaure. A majority of them suffers a warm bias in the tropical subsiding regions located over the eastern parts of oceans. These regions are usually covered by low-level clouds scattered from stratus along the coasts to more vertically developed shallow cumulus farther from them. Models usually fail to represent accurately this transition. Here we investigate physical drivers of this warm bias in CMIP5 models through a near-surface energy budget perspective. We show that overestimated solar insolation due to a lack of stratocumulus mostly explains the warm bias. This bias also arises partly from inter-model differences in surface fluxes that could be traced to differences in near-surface relative humidity and air-sea temperature gradient. We investigate the role of the atmosphere in driving surface biases by comparing historical and atmopsheric (AMIP) experiments. We show that some differences in boundary-layer characteristics, mostly those related to cloud fraction and relative humidity, are already present in AMIP experiments and may be the drivers of coupled biases. This gives insights in how models can be improved for better simulations of the tropical climate.

Keeping cool on global warming

International Nuclear Information System (INIS)

Seitz, F.; Hawkins, W.; Nierenberg, W.; Salmon, J.; Jastrow, R.; Moore, J.H.

1992-01-01

A number of scientific groups have concluded that the greenhouse effect caused by the man-made emissions of carbon dioxide and other bases has produced much or all of the rise in global temperatures. They predict that there will be an increase in greenhouse gases equivalent to a doubling of carbon dioxide by the middle of the 21st century, and that this will cause the temperature of the earth to rise by as much as 5C. According to these scientists, a temperature rise of this magnitude would cause major disruptions in the earth's ecosystem, including severe summer drought in the midwestern US and other agricultural regions. The worst-case scenarios predict a major rise in sea level as a result of the greenhouse warming, inundating areas of New York, Miami and other coastal cities as well as low-lying river deltas and islands. The lives of hundreds of millions of people would be disrupted. The available data on climate change, however, do not support these predictions, nor do they support the idea that human activity has caused, or will cause, a dangerous increase in global temperatures. As the authors make this statement, they are aware that it contradicts widespread popular opinion, as well as the technical judgments of some of their colleagues. But it would be imprudent to ignore the facts on global warming that have accumulated over the last two years. These facts indicate that theoretical estimates of the greenhouse problem have greatly exaggerated its seriousness. Enormous economic stakes ride on forthcoming government decisions regarding carbon taxes and other restrictions on CO 2 emissions. Due attention must therefore be given to the scientific evidence, no matter how contrary to popular opinion its implications appear to be. This article discusses the scientific evidence

Recent very high heat stress summers will be the norm within 20 years

Science.gov (United States)

Li, C.; Zhang, X.; Zwiers, F. W.

2017-12-01

The wet bulb globe temperature (WBGT) accounts for the effect of environmental temperature and humidity on thermal comfort, and is considered as a heat stress index most relevant to human health. In this study, we compare observation-based and modeled 1973-2012 summer WBGT over north hemispheric land between 10° N and 60° N covered by sufficient observations. We show that summer WBGT has trended upward since 1973, and that these upward trends are more likely to be anthropogenic than natural in origin. Of the observed 1.08 °C warming in summer WBGT during 1973-2012, greenhouse gas increases alone could have contributed 1.55 °C (90% confidence interval 1.04 2.25°C), which is partly offset by 0.51°C (0.01 1.20°C) cooling due to other anthropogenic forcings such as anthropogenic aerosols, ozone and land use change. At regional scales, the record summer mean WBGT experienced during 1973-2012 is now expected to be at least 70 times as likely to occur compared to if there were no anthropogenic influence. Future projections under the representative concentration pathway emissions scenario RCP8.5 that are constrained by observations indicate that within 20 years at least 50% of the future summers will have seasonal mean WBGT higher the highest in the historical record in all the analyzed regions, and that this percentage will increase dramatically to 95% by mid-century. The projected high WBGT temperatures can pose potentially dangerous impacts on human and natural systems, calling for urgent need for the development of adaptation measures.

Western US high June 2015 temperatures and their relation to global warming and soil moisture

NARCIS (Netherlands)

Philip, Sjoukje Y.; Kew, Sarah F.; Hauser, Mathias; Guillod, Benoit P.; Teuling, Adriaan J.; Whan, Kirien; Uhe, Peter; Oldenborgh, van Geert Jan

2018-01-01

The Western US states Washington (WA), Oregon (OR) and California (CA) experienced extremely high temperatures in June 2015. The temperature anomalies were so extreme that they cannot be explained with global warming alone. We investigate the hypothesis that soil moisture played an important role

Projections of Seasonal Patterns in Temperature- Related Deaths for Manhattan, New York

Science.gov (United States)

Li, Tiantian; Horton, Radley M.; Kinney, Patrick L.

2013-01-01

Global average temperatures have been rising for the past half-century, and the warming trend has accelerated in recent decades. Further warming is expected over the next few decades, with significant regional variations. These warming trends will probably result in more frequent, intense and persistent periods of hot temperatures in summer, and generally higher temperatures in winter. Daily death counts in cities increase markedly when temperatures reach levels that are very high relative to what is normal in a given location. Relatively cold temperatures also seem to carry risk. Rising temperatures may result in more heat-related mortality but may also reduce cold-related mortality, and the net impact on annual mortality remains uncertain. Here we use 16 downscaled global climate models and two emissions scenarios to estimate present and future seasonal patterns in temperature-related mortality in Manhattan, New York. All 32 projections yielded warm-season increases and cold-season decreases in temperature-related mortality, with positive net annual temperature-related deaths in all cases. Monthly analyses showed that the largest percentage increases may occur in May and September. These results suggest that, over a range of models and scenarios of future greenhouse gas emissions, increases in heat-related mortality could outweigh reductions in cold-related mortality, with shifting seasonal patterns.

Compound extremes of summer temperature and precipitation leading to intensified departures from natural variability.

Science.gov (United States)

Mahony, C. R.; Cannon, A. J.

2017-12-01

Climate change can drive local climates outside the range of their historical year-to-year variability, straining the adaptive capacity of ecological and human communities. We demonstrate that interactions between climate variables can produce larger and earlier departures from natural variability than is detectable in individual variables. For example, summer temperature (Tx) and precipitation (Pr) are negatively correlated in most terrestrial regions, such that interannual variability lies along an axis from warm-and-dry to cool-and-wet conditions. A climate change trend perpendicular to this axis, towards warmer-wetter conditions, can depart more quickly from the range of natural variability than a warmer-drier trend. This multivariate "departure intensification" effect is evident in all six CMIP5 models that we examined: 23% (9-34%) of the land area of each model exhibits a pronounced increase in 2σ extremesin the Tx-Pr regime relative to Tx or Pr alone. Observational data suggest that Tx-Pr correlations are sufficient to produce departure intensification in distinct regions on all continents. Departures from the historical Tx-Pr regime may produce ecological disruptions, such as in plant-pathogen interactions and human diseases, that could offset the drought mitigation benefits of increased precipitation. Our study alerts researchers and adaptation practitioners to the presence of multivariate climate change signals and compound extremes that are not detectable in individual climate variables.

Discharge, water temperature, and water quality of Warm Mineral Springs, Sarasota County, Florida: A retrospective analysis

Science.gov (United States)

Metz, Patricia A.

2016-09-27

in inland areas, and upward flow toward the surface in coastal areas, such as at Warm Mineral Springs. Warm Mineral Springs is located in a discharge area. Changes in water use in the region have affected the potentiometric surface of the Upper Floridan aquifer. Historical increase in groundwater withdrawals resulted in a 10- to 20-foot regional decline in the potentiometric surface of the Upper Floridan aquifer by May 1975 relative to predevelopment levels and remained at approximately that level in May 2007 in the area of Warm Mineral Springs. Discharge measurements at Warm Mineral Springs (1942–2014) decreased from about 11–12 cubic feet per second in the 1940s to about 6–9 cubic feet per second in the 1970s and remained at about that level for the remainder of the period of record. Similarity of changes in regional water use and discharge at Warm Mineral Springs indicates that basin-scale changes to the groundwater system have affected discharge at Warm Mineral Springs. Water temperature had no significant trend in temperature over the period of record, 1943–2015, and outliers were identified in the data that might indicate inconsistencies in measurement methods or locations.Within the regional groundwater basin, Warm Mineral Springs is influenced by deep Upper Floridan aquifer flow paths that discharge toward the coast. Associated with these flow paths, the groundwater temperatures increase with depth and toward the coast. Multiple lines of evidence indicate that a source of warm groundwater to Warm Mineral Springs is likely the permeable zone of the Avon Park Formation within the Upper Floridan aquifer at a depth of about 1,400 to 1,600 feet, or deeper sources. The permeable zone contains saline groundwater with water temperatures of at least 95 degrees Fahrenheit.The water quality of Warm Mineral Springs, when compared with other springs in Florida had the highest temperature and the greatest mineralized content. Warm Mineral Springs water is

Artificial asymmetric warming reduces nectar yield in a Tibetan alpine species of Asteraceae.

Science.gov (United States)

Mu, Junpeng; Peng, Youhong; Xi, Xinqiang; Wu, Xinwei; Li, Guoyong; Niklas, Karl J; Sun, Shucun

2015-11-01

Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows. A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7 °C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8 °C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology. Six years of experimental warming resulted in reductions in nectar volume per floret (64·7 % of control), floret number per capitulum (8·7 %) and capitulum number per plant (32·5 %), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90 % in nectar production per unit area. The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant-pollinator interactions and plant

Oral temperatures of the elderly in nursing homes in summer and winter in relation to activities of daily living

Science.gov (United States)

Nakamura, K.; Tanaka, Masatoshi; Motohashi, Yutaka; Maeda, Akira

This study was conducted to clarify the seasonal difference in body temperature in summer and winter, and to document the thermal environment of the elderly living in nursing homes. The subjects were 57 healthy elderly people aged >=63 years living in two nursing homes in Japan. One of the homes was characterized by subjects with low levels of activities of daily living (ADL). Oral temperatures were measured in the morning and afternoon, with simultaneous recording of ambient temperature and relative humidity. Oral temperatures in summer were higher than in winter, with statistically significant differences (Pchanges in ambient temperature.

Passive heating following the prematch warm-up in soccer: examining the time-course of changes in muscle temperature and contractile function.

Science.gov (United States)

Marshall, Paul W M; Cross, Rebecca; Lovell, Ric

2015-12-01

This study examined changes in muscle temperature, electrically evoked muscle contractile properties, and voluntary power before and after a soccer specific active warm-up and subsequent rest period. Ten amateur soccer players performed two experimental sessions that involved performance of a modified FIFA 11+ soccer specific warm-up, followed by a 12.5-min rest period where participants were required to wear either normal clothing or a passive electrical heating garment was applied to the upper thigh muscles. Assessments around the warm-up and cool-down included measures of maximal torque, rate of torque development, muscle temperature (Tm), and electrically evoked measures of quadriceps contractile function. Tm was increased after the warm-up by 3.2 ± 0.7°C (P warm-up between 20% and 30% (P warm-up did not effect variables measured. While Tm was reduced by 1.4 ± 0.4°C after the rest period (P warm-up levels. Voluntary and evoked rate of torque development remained elevated from pre warm-up levels at the end of the cool-down (P warm-up elevated muscle temperature by 3.2°C and was associated with concomitant increases of between 20% and 30% in voluntary rate of torque development, which seems explained by elevations in rate-dependent measures of intrinsic muscle contractile function. Application of a passive heating garment did not attenuate declines in muscle temperature during a 12.5-min rest period. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

How warm days increase belief in global warming

Science.gov (United States)

Zaval, Lisa; Keenan, Elizabeth A.; Johnson, Eric J.; Weber, Elke U.

2014-02-01

Climate change judgements can depend on whether today seems warmer or colder than usual, termed the local warming effect. Although previous research has demonstrated that this effect occurs, studies have yet to explain why or how temperature abnormalities influence global warming attitudes. A better understanding of the underlying psychology of this effect can help explain the public's reaction to climate change and inform approaches used to communicate the phenomenon. Across five studies, we find evidence of attribute substitution, whereby individuals use less relevant but available information (for example, today's temperature) in place of more diagnostic but less accessible information (for example, global climate change patterns) when making judgements. Moreover, we rule out alternative hypotheses involving climate change labelling and lay mental models. Ultimately, we show that present temperature abnormalities are given undue weight and lead to an overestimation of the frequency of similar past events, thereby increasing belief in and concern for global warming.

Local adaptation and the potential effects of a contaminant on predator avoidance and antipredator responses under global warming: a space-for-time substitution approach

Science.gov (United States)

Janssens, Lizanne; Dinh Van, Khuong; Debecker, Sara; Bervoets, Lieven; Stoks, Robby

2014-01-01

The ability to deal with temperature-induced changes in interactions with contaminants and predators under global warming is one of the outstanding, applied evolutionary questions. For this, it is crucial to understand how contaminants will affect activity levels, predator avoidance and antipredator responses under global warming and to what extent gradual thermal evolution may mitigate these effects. Using a space-for-time substitution approach, we assessed the potential for gradual thermal evolution shaping activity (mobility and foraging), predator avoidance and antipredator responses when Ischnura elegans damselfly larvae were exposed to zinc in a common-garden warming experiment at the mean summer water temperatures of shallow water bodies at southern and northern latitudes (24 and 20°C, respectively). Zinc reduced mobility and foraging, predator avoidance and escape swimming speed. Importantly, high-latitude populations showed stronger zinc-induced reductions in escape swimming speed at both temperatures, and in activity levels at the high temperature. The latter indicates that local thermal adaptation may strongly change the ecological impact of contaminants under global warming. Our study underscores the critical importance of considering local adaptation along natural gradients when integrating biotic interactions in ecological risk assessment, and the potential of gradual thermal evolution mitigating the effects of warming on the vulnerability to contaminants. PMID:24665344

Local adaptation and the potential effects of a contaminant on predator avoidance and antipredator responses under global warming: a space-for-time substitution approach.

Science.gov (United States)

Janssens, Lizanne; Dinh Van, Khuong; Debecker, Sara; Bervoets, Lieven; Stoks, Robby

2014-03-01

The ability to deal with temperature-induced changes in interactions with contaminants and predators under global warming is one of the outstanding, applied evolutionary questions. For this, it is crucial to understand how contaminants will affect activity levels, predator avoidance and antipredator responses under global warming and to what extent gradual thermal evolution may mitigate these effects. Using a space-for-time substitution approach, we assessed the potential for gradual thermal evolution shaping activity (mobility and foraging), predator avoidance and antipredator responses when Ischnura elegans damselfly larvae were exposed to zinc in a common-garden warming experiment at the mean summer water temperatures of shallow water bodies at southern and northern latitudes (24 and 20°C, respectively). Zinc reduced mobility and foraging, predator avoidance and escape swimming speed. Importantly, high-latitude populations showed stronger zinc-induced reductions in escape swimming speed at both temperatures, and in activity levels at the high temperature. The latter indicates that local thermal adaptation may strongly change the ecological impact of contaminants under global warming. Our study underscores the critical importance of considering local adaptation along natural gradients when integrating biotic interactions in ecological risk assessment, and the potential of gradual thermal evolution mitigating the effects of warming on the vulnerability to contaminants.

Interdecadal change of the controlling mechanisms for East Asian early summer rainfall variation around the mid-1990s

Science.gov (United States)

Yim, So-Young; Wang, Bin; Kwon, MinHo

2014-03-01

East Asian (EA) summer monsoon shows considerable differences in the mean state and principal modes of interannual variation between early summer (May-June, MJ) and late summer (July-August, JA). The present study focuses on the early summer (MJ) precipitation variability. We find that the interannual variation of the MJ precipitation and the processes controlling the variation have been changed abruptly around the mid-1990s. The rainfall anomaly represented by the leading empirical orthogonal function has changed from a dipole-like pattern in pre-95 epoch (1979-1994) to a tripole-like pattern in post-95 epoch (1995-2010); the prevailing period of the corresponding principal component has also changed from 3-5 to 2-3 years. These changes are concurrent with the changes of the corresponding El Nino-Southern Oscillation (ENSO) evolutions. During the pre-95 epoch, the MJ EA rainfall anomaly is coupled to a slow decay of canonical ENSO events signified by an eastern Pacific warming, which induces a dipole rainfall feature over EA. On the other hand, during the post-95 epoch the anomalous MJ EA rainfall is significantly linked to a rapid decay of a central Pacific warming and a distinct tripolar sea surface temperature (SST) in North Atlantic. The central Pacific warming-induced Philippine Sea anticyclone induces an increased rainfall in southern China and decreased rainfall in central eastern China. The North Atlantic Oscillation-related tripolar North Atlantic SST anomaly induces a wave train that is responsible for the increase northern EA rainfall. Those two impacts form the tripole-like rainfall pattern over EA. Understanding such changes is important for improving seasonal to decadal predictions and long-term climate change in EA.

Temperature extremes in Europe: mechanisms and responses to climatic change

International Nuclear Information System (INIS)

Cattiaux, Julien

2010-01-01

Europe witnessed a spate of record-breaking warm seasons during the 2000's. As illustrated by the devastating heat-wave of the summer 2003, these episodes induced strong societal and environmental impacts. Such occurrence of exceptional events over a relatively short time period raised up many questionings in the present context of climate change. In particular, can recent temperature extremes be considered as 'previews' of future climate conditions? Do they result from an increasing temperature variability? These questions constitute the main motivations of this thesis. Thus, our work aims to contribute to the understanding of physical mechanisms responsible for seasonal temperature extremes in Europe, in order to anticipate their future statistical characteristics. Involved processes are assessed by both statistical data-analysis of observations and climate projections and regional modeling experiments. First we show that while the inter-annual European temperature variability appears driven by disturbances in the North-Atlantic dynamics, the recent warming is likely to be dissociated with potential circulation changes. This inconsistency climaxes during the exceptionally mild autumn of 2006, whose temperature anomaly is only half explained by the atmospheric flow. Recent warm surface conditions in the North-Atlantic ocean seem to substantially contribute to the European warming in autumn-winter, through the establishment of advective and radiative processes. In spring-summer, since both advection by the westerlies and Atlantic warming are reduced, more local processes appear predominant (e.g. soil moisture, clouds, aerosols). Then the issue of future evolution of the relationship between North-Atlantic dynamics and European temperatures is addressed, based on climate projections of the International Panel on Climate Change. Multi-model analysis, using both flow-analogues and weather regimes methods, show that the inconsistency noticed over recent decades is

Impact of cool versus warm temperatures on gestation in the aspic viper (Vipera aspis).

Science.gov (United States)

Michel, Catherine Louise; Pastore, Jean-Henri; Bonnet, Xavier

2013-07-01

Previous experimental data suggested that digestion and growth rates are not impaired under cool constant temperature (23°C) in a viviparous snake (Vipera aspis). These results challenged the widespread notion that both elevated temperatures (e.g. 30°C) and temperature fluctuations are required for digestion and growth in temperate climate reptiles. Here, we investigated the impact of constant cool temperatures on another physiological performance that is crucial to population persistence: gestation. At the time when reproductive females were midway through vitellogenesis, we placed ten reproductive and two non-reproductive female aspic vipers at each of two contrasted constant temperature conditions: cool (23°C) versus warm (28°C). Sixty percent of the females placed at 28°C gave birth to healthy offspring, suggesting that constant warm body temperatures were compatible with normal offspring production. Conversely, none of the cool females gave birth to healthy offspring. A blister disease affected exclusively cool pregnant females. Apparently, the combination of cool temperatures plus gestation was too challenging for such females. Our results suggest that reproduction is more thermally sensitive than digestion or growth, indeed gestation faltered under moderately cool thermal constraints. This sensitivity could be a crucial factor determining the capacity of this species to colonize different habitats. Copyright © 2013 Elsevier Inc. All rights reserved.

Uncertain impacts on economic growth when stabilizing global temperatures at 1.5°C or 2°C warming

Science.gov (United States)

Pretis, Felix; Schwarz, Moritz; Tang, Kevin; Haustein, Karsten; Allen, Myles R.

2018-05-01

Empirical evidence suggests that variations in climate affect economic growth across countries over time. However, little is known about the relative impacts of climate change on economic outcomes when global mean surface temperature (GMST) is stabilized at 1.5°C or 2°C warming relative to pre-industrial levels. Here we use a new set of climate simulations under 1.5°C and 2°C warming from the `Half a degree Additional warming, Prognosis and Projected Impacts' (HAPPI) project to assess changes in economic growth using empirical estimates of climate impacts in a global panel dataset. Panel estimation results that are robust to outliers and breaks suggest that within-year variability of monthly temperatures and precipitation has little effect on economic growth beyond global nonlinear temperature effects. While expected temperature changes under a GMST increase of 1.5°C lead to proportionally higher warming in the Northern Hemisphere, the projected impact on economic growth is larger in the Tropics and Southern Hemisphere. Accounting for econometric estimation and climate uncertainty, the projected impacts on economic growth of 1.5°C warming are close to indistinguishable from current climate conditions, while 2°C warming suggests statistically lower economic growth for a large set of countries (median projected annual growth up to 2% lower). Level projections of gross domestic product (GDP) per capita exhibit high uncertainties, with median projected global average GDP per capita approximately 5% lower at the end of the century under 2°C warming relative to 1.5°C. The correlation between climate-induced reductions in per capita GDP growth and national income levels is significant at the p economic inequality between countries and is relevant to discussions of loss and damage under the United Nations Framework Convention on Climate Change. This article is part of the theme issue `The Paris Agreement: understanding the physical and social challenges for a

Uncertain impacts on economic growth when stabilizing global temperatures at 1.5°C or 2°C warming

Science.gov (United States)

Schwarz, Moritz; Tang, Kevin; Haustein, Karsten; Allen, Myles R.

2018-01-01

Empirical evidence suggests that variations in climate affect economic growth across countries over time. However, little is known about the relative impacts of climate change on economic outcomes when global mean surface temperature (GMST) is stabilized at 1.5°C or 2°C warming relative to pre-industrial levels. Here we use a new set of climate simulations under 1.5°C and 2°C warming from the ‘Half a degree Additional warming, Prognosis and Projected Impacts' (HAPPI) project to assess changes in economic growth using empirical estimates of climate impacts in a global panel dataset. Panel estimation results that are robust to outliers and breaks suggest that within-year variability of monthly temperatures and precipitation has little effect on economic growth beyond global nonlinear temperature effects. While expected temperature changes under a GMST increase of 1.5°C lead to proportionally higher warming in the Northern Hemisphere, the projected impact on economic growth is larger in the Tropics and Southern Hemisphere. Accounting for econometric estimation and climate uncertainty, the projected impacts on economic growth of 1.5°C warming are close to indistinguishable from current climate conditions, while 2°C warming suggests statistically lower economic growth for a large set of countries (median projected annual growth up to 2% lower). Level projections of gross domestic product (GDP) per capita exhibit high uncertainties, with median projected global average GDP per capita approximately 5% lower at the end of the century under 2°C warming relative to 1.5°C. The correlation between climate-induced reductions in per capita GDP growth and national income levels is significant at the p economic inequality between countries and is relevant to discussions of loss and damage under the United Nations Framework Convention on Climate Change. This article is part of the theme issue ‘The Paris Agreement: understanding the physical and social challenges for

Impact of energy consumption on urban warming and air pollution in Tokyo metropolitan area

International Nuclear Information System (INIS)

Saitoh, T.S.; Hoshi, H.

1995-01-01

The rapid progress of industrialization and urbanization due to economic growth and concentration of social function in the urban areas in Japan have had an adverse effect on the urban environment. In most cities, it has become evident that the increase in energy consumption is causing environmental problems, including a temperature rise in the urban atmosphere (urban heat island) and air pollution. This paper reports the results of field observations and three dimensional simulations of the urban heat island using a three-dimensional modelling vorticity-velocity vector potential formation, in the Tokyo metropolitan area. According to the simulation for urban warming in the study area for the year 2031, the maximum temperature of a summer evening (18:00) would exceed 43 degrees celsius, indicating that Tokyo would no longer be comfortable for its inhabitants. It is concluded that in the near future, the problem of the urban heat island will become a more important issue than that of global warming because the rate of urban warming is greater. For this reason, the urban heat island could be fatal to humans unless resolved in the near future. (author). 1 tab., 11 figs., 18 refs

Recent warming of lake Kivu.

Science.gov (United States)

Katsev, Sergei; Aaberg, Arthur A; Crowe, Sean A; Hecky, Robert E

2014-01-01

Lake Kivu in East Africa has gained notoriety for its prodigious amounts of dissolved methane and dangers of limnic eruption. Being meromictic, it is also expected to accumulate heat due to rising regional air temperatures. To investigate the warming trend and distinguish between atmospheric and geothermal heating sources, we compiled historical temperature data, performed measurements with logging instruments, and simulated heat propagation. We also performed isotopic analyses of water from the lake's main basin and isolated Kabuno Bay. The results reveal that the lake surface is warming at the rate of 0.12°C per decade, which matches the warming rates in other East African lakes. Temperatures increase throughout the entire water column. Though warming is strongest near the surface, warming rates in the deep waters cannot be accounted for solely by propagation of atmospheric heat at presently assumed rates of vertical mixing. Unless the transport rates are significantly higher than presently believed, this indicates significant contributions from subterranean heat sources. Temperature time series in the deep monimolimnion suggest evidence of convection. The progressive deepening of the depth of temperature minimum in the water column is expected to accelerate the warming in deeper waters. The warming trend, however, is unlikely to strongly affect the physical stability of the lake, which depends primarily on salinity gradient.

Recent warming of lake Kivu.

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Sergei Katsev

Full Text Available Lake Kivu in East Africa has gained notoriety for its prodigious amounts of dissolved methane and dangers of limnic eruption. Being meromictic, it is also expected to accumulate heat due to rising regional air temperatures. To investigate the warming trend and distinguish between atmospheric and geothermal heating sources, we compiled historical temperature data, performed measurements with logging instruments, and simulated heat propagation. We also performed isotopic analyses of water from the lake's main basin and isolated Kabuno Bay. The results reveal that the lake surface is warming at the rate of 0.12°C per decade, which matches the warming rates in other East African lakes. Temperatures increase throughout the entire water column. Though warming is strongest near the surface, warming rates in the deep waters cannot be accounted for solely by propagation of atmospheric heat at presently assumed rates of vertical mixing. Unless the transport rates are significantly higher than presently believed, this indicates significant contributions from subterranean heat sources. Temperature time series in the deep monimolimnion suggest evidence of convection. The progressive deepening of the depth of temperature minimum in the water column is expected to accelerate the warming in deeper waters. The warming trend, however, is unlikely to strongly affect the physical stability of the lake, which depends primarily on salinity gradient.

Evaluation of the Atlantic Multidecadal Oscillation Impact on Large-Scale Atmospheric Circulation in the Atlantic Region in Summer

Science.gov (United States)

Semenov, V. A.; Cherenkova, E. A.

2018-02-01

The influence of the Atlantic Multidecadal Oscillation (AMO) on large-scale atmospheric circulation in the Atlantic region in summer for the period of 1950-2015 is investigated. It is shown that the intensification of the summer North Atlantic Oscillation (NAO) with significant changes in sea level pressure anomalies in the main centers of action (over Greenland and the British Isles) occurred while the North Atlantic was cooler. Sea surface temperature anomalies, which are linked to the AMO in the summer season, affect both the NAO index and fluctuations of the Eastern Atlantic/Western Russia (EAWR) centers of action. The positive (negative) phase of the AMO is characterized by a combination of negative (positive) values of the NAO and EAWR indices. The dominance of the opposite phases of the teleconnection indices in summer during the warm North Atlantic and in its colder period resulted in differences in the regional climate in Europe.

Seasonal and elevational contrasts in temperature trends in Central Chile between 1979 and 2015

Science.gov (United States)

Burger, F.; Brock, B.; Montecinos, A.

2018-03-01

We analyze trends in temperature from 18 temperature stations and one upper air sounding site at 30°-35° S in central Chile between 1979-2015, to explore geographical and season temperature trends and their controls, using regional ocean-atmosphere indices. Significant warming trends are widespread at inland stations, while trends are non-significant or negative at coastal sites, as found in previous studies. However, ubiquitous warming across the region in the past 8 years, suggests the recent period of coastal cooling has ended. Significant warming trends are largely restricted to austral spring, summer and autumn seasons, with very few significant positive or negative trends in winter identified. Autumn warming is notably strong in the Andes, which, together with significant warming in spring, could help to explain the negative mass balance of snow and glaciers in the region. A strong Pacific maritime influence on regional temperature trends is inferred through correlation with the Interdecadal Pacific Oscillation (IPO) index and coastal sea surface temperature, but the strength of this influence rapidly diminishes inland, and the majority of valley, and all Andes, sites are independent of the IPO index. Instead, valley and Andes sites, and mid-troposphere temperature in the coastal radiosonde profile, show correlation with the autumn Antarctic Oscillation which, in its current positive phase, promotes subsidence and warming at the latitude of central Chile.

Coupling between marine boundary layer clouds and summer-to-summer sea surface temperature variability over the North Atlantic and Pacific

Science.gov (United States)

Myers, Timothy A.; Mechoso, Carlos R.; DeFlorio, Michael J.

2018-02-01

Climate modes of variability over the Atlantic and Pacific may be amplified by a positive feedback between sea-surface temperature (SST) and marine boundary layer clouds. However, it is well known that climate models poorly simulate this feedback. Does this deficiency contribute to model-to-model differences in the representation of climate modes of variability? Over both the North Atlantic and Pacific, typical summertime interannual to interdecadal SST variability exhibits horseshoe-like patterns of co-located anomalies of shortwave cloud radiative effect (CRE), low-level cloud fraction, SST, and estimated inversion strength over the subtropics and midlatitudes that are consistent with a positive cloud feedback. During winter over the midlatitudes, this feedback appears to be diminished. Models participating in the Coupled Model Intercomparison Project phase 5 that simulate a weak feedback between subtropical SST and shortwave CRE produce smaller and less realistic amplitudes of summertime SST and CRE variability over the northern oceans compared to models with a stronger feedback. The change in SST amplitude per unit change in CRE amplitude among the models and observations may be understood as the temperature response of the ocean mixed layer to a unit change in radiative flux over the course of a season. These results highlight the importance of boundary layer clouds in interannual to interdecadal atmosphere-ocean variability over the northern oceans during summer. The results also suggest that deficiencies in the simulation of these clouds in coupled climate models contribute to underestimation in their simulation of summer-to-summer SST variability.

Analysis of surface air temperature variations and local urbanization effects on central Yunnan Plateau, SW China

Science.gov (United States)

He, Yunling; Wu, Zhijie; Liu, Xuelian; Deng, Fuying

2018-01-01

With the surface air temperature (SAT) data at 37 stations on Central Yunnan Plateau (CYP) for 1961-2010 and the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data, the temporal-spatial patterns of the SAT trends are detected using Sen's Nonparametric Estimator of Slope approach and MK test, and the impact of urbanization on surface warming is analyzed by comparing the differences between the air temperature change trends of urban stations and their corresponding rural stations. Results indicated that annual mean air temperature showed a significant warming trend, which is equivalent to a rate of 0.17 °C/decade during the past 50 years. Seasonal mean air temperature presents a rising trend, and the trend was more significant in winter (0.31 °C/decade) than in other seasons. Annual/seasonal mean air temperature tends to increase in most areas, and higher warming trend appeared in urban areas, notably in Kunming city. The regional mean air temperature series was significantly impacted by urban warming, and the urbanization-induced warming contributed to approximately 32.3-62.9 % of the total regional warming during the past 50 years. Meantime, the urbanization-induced warming trend in winter and spring was more significant than that in summer and autumn. Since 1985, the urban heat island (UHI) intensity has gradually increased. And the urban temperatures always rise faster than rural temperatures on the CYP.

Case study: Investigating the causes of temperature breaks in South African summer fruit export cold chains

CSIR Research Space (South Africa)

Goedhals-Gerber, LL

2016-08-01

Full Text Available This study investigated the causes and extent of temperature breaks in the South African summer fruit export cold chain from the pack house to the vessel. Numerous causes of temperature breaks throughout the cold chain were found, resulting in many...

Methods of patient warming during abdominal surgery.

Directory of Open Access Journals (Sweden)

Li Shao

Full Text Available BACKGROUND: Keeping abdominal surgery patients warm is common and warming methods are needed in power outages during natural disasters. We aimed to evaluate the efficacy of low-cost, low-power warming methods for maintaining normothermia in abdominal surgery patients. METHODS: Patients (n = 160 scheduled for elective abdominal surgery were included in this prospective clinical study. Five warming methods were applied: heated blood transfusion/fluid infusion vs. unheated; wrapping patients vs. not wrapping; applying moist dressings, heated or not; surgical field rinse heated or not; and applying heating blankets or not. Patients' nasopharyngeal and rectal temperatures were recorded to evaluate warming efficacy. Significant differences were found in mean temperatures of warmed patients compared to those not warmed. RESULTS: When we compared temperatures of abdominal surgery patient groups receiving three specific warming methods with temperatures of control groups not receiving these methods, significant differences were revealed in temperatures maintained during the surgeries between the warmed groups and controls. DISCUSSION: The value of maintaining normothermia in patients undergoing abdominal surgery under general anesthesia is accepted. Three effective economical and practically applicable warming methods are combined body wrapping and heating blanket; combined body wrapping, heated moist dressings, and heating blanket; combined body wrapping, heated moist dressings, and warmed surgical rinse fluid, with or without heating blanket. These methods are practically applicable when low-cost method is indeed needed.

Experimental warming differentially affects microbial structure and activity in two contrasted moisture sites in a Sphagnum-dominated peatland.

Science.gov (United States)

Delarue, Frédéric; Buttler, Alexandre; Bragazza, Luca; Grasset, Laurent; Jassey, Vincent E J; Gogo, Sébastien; Laggoun-Défarge, Fatima

2015-04-01

Several studies on the impact of climate warming have indicated that peat decomposition/mineralization will be enhanced. Most of these studies deal with the impact of experimental warming during summer when prevalent abiotic conditions are favorable to decomposition. Here, we investigated the effect of experimental air warming by open-top chambers (OTCs) on water-extractable organic matter (WEOM), microbial biomasses and enzymatic activities in two contrasted moisture sites named Bog and Fen sites, the latter considered as the wetter ones. While no or few changes in peat temperature and water content appeared under the overall effect of OTCs, we observed that air warming smoothed water content differences and led to a decrease in mean peat temperature at the warmed Bog sites. This thermal discrepancy between the two sites led to contrasting changes in microbial structure and activities: a rise in hydrolytic activity at the warmed Bog sites and a relative enhancement of bacterial biomass at the warmed Fen sites. These features were not associated with any change in WEOM properties namely carbon and sugar contents and aromaticity, suggesting that air warming did not trigger any shift in OM decomposition. Using various tools, we show that the use of single indicators of OM decomposition can lead to fallacious conclusions. Lastly, these patterns may change seasonally as a consequence of complex interactions between groundwater level and air warming, suggesting the need to improve our knowledge using a high time-resolution approach. Copyright © 2015 Elsevier B.V. All rights reserved.

Animal physiology. Summer declines in activity and body temperature offer polar bears limited energy savings.

Science.gov (United States)

Whiteman, J P; Harlow, H J; Durner, G M; Anderson-Sprecher, R; Albeke, S E; Regehr, E V; Amstrup, S C; Ben-David, M

2015-07-17

Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of "ice" bears in summer is unknown, "shore" bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation. Copyright © 2015, American Association for the Advancement of Science.

Extreme summer temperatures in Iberia: health impacts and associated synoptic conditions

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R. García-Herrera

2005-02-01

Full Text Available This paper examines the effect of extreme summer temperatures on daily mortality in two large cities of Iberia: Lisbon (Portugal and Madrid (Spain. Daily mortality and meteorological variables are analysed using the same methodology based on Box-Jenkins models. Results reveal that in both cases there is a triggering effect on mortality when maximum daily temperature exceeds a given threshold (34°C in Lisbon and 36°C in Madrid. The impact of most intense heat events is very similar for both cities, with significant mortality values occurring up to 3 days after the temperature threshold has been surpassed. This impact is measured as the percentual increase of mortality associated to a 1°C increase above the threshold temperature. In this respect, Lisbon shows a higher impact, 31%, as compared with Madrid at 21%. The difference can be attributed to demographic and socio-economic factors. Furthermore, the longer life span of Iberian women is critical to explain why, in both cities, females are more susceptible than males to heat effects, with an almost double mortality impact value. The analysis of Sea Level Pressure (SLP, 500hPa geopotential height and temperature fields reveals that, despite being relatively close to each other, Lisbon and Madrid have relatively different synoptic circulation anomalies associated with their respective extreme summer temperature days. The SLP field reveals higher anomalies for Lisbon, but extending over a smaller area. Extreme values in Madrid seem to require a more western location of the Azores High, embracing a greater area over Europe, even if it is not as deep as for Lisbon. The origin of the hot and dry air masses that usually lead to extreme heat days in both cities is located in Northern Africa. However, while Madrid maxima require wind blowing directly from the south, transporting heat from Southern Spain and Northern Africa, Lisbon maxima occur under more easterly conditions, when Northern African air

Extreme summer temperatures in Iberia: health impacts and associated synoptic conditions

Directory of Open Access Journals (Sweden)

R. García-Herrera

2005-02-01

Full Text Available This paper examines the effect of extreme summer temperatures on daily mortality in two large cities of Iberia: Lisbon (Portugal and Madrid (Spain. Daily mortality and meteorological variables are analysed using the same methodology based on Box-Jenkins models. Results reveal that in both cases there is a triggering effect on mortality when maximum daily temperature exceeds a given threshold (34°C in Lisbon and 36°C in Madrid. The impact of most intense heat events is very similar for both cities, with significant mortality values occurring up to 3 days after the temperature threshold has been surpassed. This impact is measured as the percentual increase of mortality associated to a 1°C increase above the threshold temperature. In this respect, Lisbon shows a higher impact, 31%, as compared with Madrid at 21%. The difference can be attributed to demographic and socio-economic factors. Furthermore, the longer life span of Iberian women is critical to explain why, in both cities, females are more susceptible than males to heat effects, with an almost double mortality impact value.

The analysis of Sea Level Pressure (SLP, 500hPa geopotential height and temperature fields reveals that, despite being relatively close to each other, Lisbon and Madrid have relatively different synoptic circulation anomalies associated with their respective extreme summer temperature days. The SLP field reveals higher anomalies for Lisbon, but extending over a smaller area. Extreme values in Madrid seem to require a more western location of the Azores High, embracing a greater area over Europe, even if it is not as deep as for Lisbon. The origin of the hot and dry air masses that usually lead to extreme heat days in both cities is located in Northern Africa. However, while Madrid maxima require wind blowing directly from the south, transporting heat from Southern Spain and Northern Africa, Lisbon maxima occur under more easterly

Influences of spawning timing, water temperature, and climatic warming on early life history phenology in western Alaska sockeye salmon

Science.gov (United States)

Sparks, Morgan M.; Falke, Jeffrey A.; Quinn, Thomas P.; Adkison, Milo D.; Schindler, Daniel E.; Bartz, Krista K.; Young, Daniel B.; Westley, Peter A. H.

2018-01-01

We applied an empirical model to predict hatching and emergence timing for 25 western Alaska sockeye salmon (Oncorhynchus nerka) populations in four lake-nursery systems to explore current patterns and potential responses of early life history phenology to warming water temperatures. Given experienced temperature regimes during development, we predicted hatching to occur in as few as 58 d to as many as 260 d depending on spawning timing and temperature. For a focal lake spawning population, our climate-lake temperature model predicted a water temperature increase of 0.7 to 1.4 °C from 2015 to 2099 during the incubation period, which translated to a 16 d to 30 d earlier hatching timing. The most extreme scenarios of warming advanced development by approximately a week earlier than historical minima and thus climatic warming may lead to only modest shifts in phenology during the early life history stage of this population. The marked variation in the predicted timing of hatching and emergence among populations in close proximity on the landscape may serve to buffer this metapopulation from climate change.

[The innovation of warm disease theory in the Ming Dynasty before Wen yi lun On Pestilence].

Science.gov (United States)

Zhang, Zhi-bin

2008-10-01

Some doctors of the Ming dynasty raised subversive doubts against the traditional viewpoints of "exogenous cold disease is warm-heat" before the emergence of Wen yi lun (On Pestilence), holding that warm-heat disease "is contracted in different seasons instead of being transformed from cold to warm and/or heat". The conception of the separation of warm-heat disease and exogenous cold disease had changed from obscure to clear. As the idea became clear, the recognition on the new affection of warm, heat, summer-heat, pestilent pathogen was formed, and the idea that the pathogens of summer-heat and warm entered the human body through the mouth and nostrils was put forward. The six-channel syndrome differentiation of warm disease and the five sweat-resolving methods in pestilence raised by the doctors of this period are the aspects of the differential diagnosis of syndrome and treatment in warm diseases, and deserve to be paid attention to.

Climate and land cover effects on the temperature of Puget Sound streams: Assessment of Climate and Land Use Impacts on Stream Temperature

Energy Technology Data Exchange (ETDEWEB)

Cao, Qian [Department of Geography, University of California, Los Angeles, Los Angeles CA USA; Sun, Ning [Civil and Environmental Engineering, University of Washington, Seattle WA USA; Pacific Northwest National Laboratory, Richland WA USA; Yearsley, John [Civil and Environmental Engineering, University of Washington, Seattle WA USA; Nijssen, Bart [Civil and Environmental Engineering, University of Washington, Seattle WA USA; Lettenmaier, Dennis P. [Department of Geography, University of California, Los Angeles, Los Angeles CA USA

2016-03-06

We apply an integrated hydrology-stream temperature modeling system, DHSVM-RBM, to examine the response of the temperature of the major streams draining to Puget Sound to land cover and climate change. We first show that the model construct is able to reconstruct observed historic streamflow and stream temperature variations at a range of time scales. We then explore the relative effect of projected future climate and land cover change, including riparian vegetation, on streamflow and stream temperature. Streamflow in summer is likely to decrease as the climate warms especially in snowmelt-dominated and transient river basins despite increased streamflow in their lower reaches associated with urbanization. Changes in streamflow also result from changes in land cover, and changes in stream shading result from changes in riparian vegetation, both of which influence stream temperature. However, we find that the effect of riparian vegetation changes on stream temperature is much greater than land cover change over the entire basin especially during summer low flow periods. Furthermore, while future projected precipitation change will have relatively modest effects on stream temperature, projected future air temperature increases will result in substantial increases in stream temperature especially in summer. These summer stream temperature increases will be associated both with increasing air temperature, and projected decreases in low flows. We find that restoration of riparian vegetation could mitigate much of the projected summer stream temperature increases. We also explore the contribution of riverine thermal loadings to the heat balance of Puget Sound, and find that the riverine contribution is greatest in winter, when streams account for up to 1/8 of total thermal inputs (averaged from December through February), with larger effects in some sub-basins. We project that the riverine impact on thermal inputs to Puget Sound will become greater with both urbanization

THE INFLUENCE OF MONK EQUIPPED PONDS ON THE QUALITY OF BASIN HEAD STREAMS, THE EXAMPLE OF WATER TEMPERATURE IN LIMOUSIN AND BERRY (FRANCE

Directory of Open Access Journals (Sweden)

Laurent TOUCHART

2010-12-01

Full Text Available In the centre-west regions of France, the deep water outlet system known as a “monk” is used in 13% of bodies of water. The authorities are strongly encouraging this to increase, arguing that this system would reduce pond induced warming of the hydrographical network. We have measured the water temperature in four monk equipped ponds for 13 years to such an extent that this paper draws on an analysis of 142,200 original measurements. Compared to a surface outflow, a monk is a system which shifts the warming of the emissary water course to the end of summer and the autumn which reduces average annual warming by about 1°C. This reduces the heating of diurnal maxima but increases warming of the minima. A monk equipped pond warms the river with deep water which has acquired its heat by mechanical convection generated by the wind, as opposed to a weir equipped pond which provides surface water warmed by insolation. In winter the monk equipped pond does not damage the thermal living conditions for Fario trout embryos and larvae under the gravel. In summer, the monk prevents night time cooling of the emissary and increases the temperature of the minima excessively for sensitive species.

A methodological critique on using temperature-conditioned resampling for climate projections as in the paper of Gerstengarbe et al. (2013) winter storm- and summer thunderstorm-related loss events in Theoretical and Applied Climatology (TAC)

Science.gov (United States)

Wechsung, Frank; Wechsung, Maximilian

2016-11-01

The STatistical Analogue Resampling Scheme (STARS) statistical approach was recently used to project changes of climate variables in Germany corresponding to a supposed degree of warming. We show by theoretical and empirical analysis that STARS simply transforms interannual gradients between warmer and cooler seasons into climate trends. According to STARS projections, summers in Germany will inevitably become dryer and winters wetter under global warming. Due to the dominance of negative interannual correlations between precipitation and temperature during the year, STARS has a tendency to generate a net annual decrease in precipitation under mean German conditions. Furthermore, according to STARS, the annual level of global radiation would increase in Germany. STARS can be still used, e.g., for generating scenarios in vulnerability and uncertainty studies. However, it is not suitable as a climate downscaling tool to access risks following from changing climate for a finer than general circulation model (GCM) spatial scale.

Atmospheric summer teleconnections and Greenland Ice Sheet surface mass variations: insights from MERRA-2

International Nuclear Information System (INIS)

Lim, Young-Kwon; Schubert, Siegfried D; Molod, Andrea M; Cullather, Richard I; Zhao, Bin; Nowicki, Sophie M J; Lee, Jae N; Velicogna, Isabella

2016-01-01

The relationship between leading atmospheric teleconnection patterns and Greenland Ice Sheet (GrIS) temperature, precipitation, and surface mass balance (SMB) are investigated for the last 36 summers (1979–2014) based on Modern-Era Retrospective analysis for Research and Applications version 2 reanalyses. The results indicate that the negative phase of both the North Atlantic Oscillation (NAO) and Arctic Oscillation, associated with warm and dry conditions for the GrIS, lead to SMB decreases within 0–1 months. Furthermore, the positive phase of the East Atlantic (EA) pattern often lags the negative NAO, reflecting a dynamical linkage between these modes that acts to further enhance the warm and dry conditions over the GrIS, leading to a favorable environment for enhanced surface mass loss. The development of a strong negative NAO in combination with a strong positive EA in recent years leads to significantly larger GrIS warming compared to when the negative NAO occurs in combination with a negative or weak positive EA (0.69 K versus 0.13 K anomaly). During 2009 and 2011, weakened (as compared to conditions during the severe surface melt cases of 2010 and 2012) local high pressure blocking produced colder northerly flow over the GrIS inhibiting warming despite the occurrence of a strong negative NAO, reflecting an important role for the EA during those years. In particular, the EA acts with the NAO to enhance warming in 2010 and 2012, and weaken high pressure blocking in 2009 and 2011. In general, high pressure blocking primarily impacts the western areas of the GrIS via advective temperature increases, while changes in net surface radiative fluxes account for both western and eastern GrIS temperature changes. (letter)

Extreme temperatures in Southeast Asia caused by El Niño and worsened by global warming.

Science.gov (United States)

Thirumalai, Kaustubh; DiNezio, Pedro N; Okumura, Yuko; Deser, Clara

2017-06-06

In April 2016, southeast Asia experienced surface air temperatures (SATs) that surpassed national records, exacerbated energy consumption, disrupted agriculture and caused severe human discomfort. Here we show using observations and an ensemble of global warming simulations the combined impact of the El Niño/Southern Oscillation (ENSO) phenomenon and long-term warming on regional SAT extremes. We find a robust relationship between ENSO and southeast Asian SATs wherein virtually all April extremes occur during El Niño years. We then quantify the relative contributions of long-term warming and the 2015-16 El Niño to the extreme April 2016 SATs. The results indicate that global warming increases the likelihood of record-breaking April extremes where we estimate that 29% of the 2016 anomaly was caused by warming and 49% by El Niño. These post-Niño Aprils can potentially be anticipated a few months in advance, and thus, help societies prepare for the projected continued increases in extremes.

Winter warming as an important co-driver for Betula nana growth in western Greenland during the past century

DEFF Research Database (Denmark)

Hollesen, Jørgen; Buchwal, Agata; Rachlewicz, Grzegorz

2015-01-01

Growing season conditions are widely recognized as the main driver for tundra shrub radial growth, but the effects of winter warming and snow remain an open question. Here, we present a more than 100years long Betulanana ring-width chronology from Disko Island in western Greenland that demonstrates...... a highly significant and positive growth response to both summer and winter air temperatures during the past century. The importance of winter temperatures for Betulanana growth is especially pronounced during the periods from 1910-1930 to 1990-2011 that were dominated by significant winter warming....... Data also reveal a clear shift within the last 20years from a period with thick snow depths (1991-1996) and a positive effect on Betulanana radial growth, to a period (1997-2011) with generally very shallow snow depths and no significant growth response towards snow. During this period, winter...

High-Resolution Dynamical Downscaling Ensemble Projections of Future Extreme Temperature Distributions for the United States

Science.gov (United States)

Zobel, Zachary; Wang, Jiali; Wuebbles, Donald J.; Kotamarthi, V. Rao

2017-12-01

The aim of this study is to examine projections of extreme temperatures over the continental United States (CONUS) for the 21st century using an ensemble of high spatial resolution dynamically downscaled model simulations with different boundary conditions. The downscaling uses the Weather Research and Forecast model at a spatial resolution of 12 km along with outputs from three different Coupled Model Intercomparison Project Phase 5 global climate models that provide boundary conditions under two different future greenhouse gas (GHG) concentration trajectories. The results from two decadal-length time slices (2045-2054 and 2085-2094) are compared with a historical decade (1995-2004). Probability density functions of daily maximum/minimum temperatures are analyzed over seven climatologically cohesive regions of the CONUS. The impacts of different boundary conditions as well as future GHG concentrations on extreme events such as heat waves and days with temperature higher than 95°F are also investigated. The results show that the intensity of extreme warm temperature in future summer is significantly increased, while the frequency of extreme cold temperature in future winter decreases. The distribution of summer daily maximum temperature experiences a significant warm-side shift and increased variability, while the distribution of winter daily minimum temperature is projected to have a less significant warm-side shift with decreased variability. Using "business-as-usual" scenario, 5-day heat waves are projected to occur at least 5-10 times per year in most CONUS and ≥95°F days will increase by 1-2 months by the end of the century.

Uncertain impacts on economic growth when stabilizing global temperatures at 1.5°C or 2°C warming.

Science.gov (United States)

Pretis, Felix; Schwarz, Moritz; Tang, Kevin; Haustein, Karsten; Allen, Myles R

2018-05-13

Empirical evidence suggests that variations in climate affect economic growth across countries over time. However, little is known about the relative impacts of climate change on economic outcomes when global mean surface temperature (GMST) is stabilized at 1.5°C or 2°C warming relative to pre-industrial levels. Here we use a new set of climate simulations under 1.5°C and 2°C warming from the 'Half a degree Additional warming, Prognosis and Projected Impacts' (HAPPI) project to assess changes in economic growth using empirical estimates of climate impacts in a global panel dataset. Panel estimation results that are robust to outliers and breaks suggest that within-year variability of monthly temperatures and precipitation has little effect on economic growth beyond global nonlinear temperature effects. While expected temperature changes under a GMST increase of 1.5°C lead to proportionally higher warming in the Northern Hemisphere, the projected impact on economic growth is larger in the Tropics and Southern Hemisphere. Accounting for econometric estimation and climate uncertainty, the projected impacts on economic growth of 1.5°C warming are close to indistinguishable from current climate conditions, while 2°C warming suggests statistically lower economic growth for a large set of countries (median projected annual growth up to 2% lower). Level projections of gross domestic product (GDP) per capita exhibit high uncertainties, with median projected global average GDP per capita approximately 5% lower at the end of the century under 2°C warming relative to 1.5°C. The correlation between climate-induced reductions in per capita GDP growth and national income levels is significant at the p  < 0.001 level, with lower-income countries experiencing greater losses, which may increase economic inequality between countries and is relevant to discussions of loss and damage under the United Nations Framework Convention on Climate Change.This article is part of

Perception of foot temperature in young women with cold constitution: analysis of skin temperature and warm and cold sensation thresholds.

Science.gov (United States)

Sadakata, Mieko; Yamada, Yoshiaki

2007-06-01

To examine the disease state of cold constitution, physiological measurements of the foot were conducted by investigating thermal sensations under an environmental condition of 25 degrees C-26 degrees C (neutral temperature) in 29 young women with and without cold constitution. The subjects were classified into 3 groups according to their experiences with cold constitution: cold constitution, intermediate, and normal groups. Foot skin temperature was measured by thermography. Thermal sensations were measured on the dorsum of the left foot using a thermal stimulator. Cold and warm spots on the dorsum of the right foot were ascertained. Thermal stimulation was delivered by a copper probe. No significant differences in foot skin temperature among these 3 groups were identified as measured in a laboratory under neutral temperature conditions. However, the mean warm sensation threshold was +6.3+/-1.09 degrees C (mean+/-SEM) for the cold constitution group (n=14), +3.4+/-2.10 degrees C (mean+/-SEM) for the intermediate group (n=7), and -0.25+/-1.96 degrees C (mean+/-SEM) for the normal group (n=6). The difference was significant between the cold constitution and normal groups. No significant differences among the 3 groups were found in the cold sensation threshold. This may be attributable to the distribution of thermal receptors and to chronically reduced blood flow in subcutaneous tissues, where the skin temperature receptors responsible for temperature sensation are located.

Separating climate change signals into thermodynamic, lapse-rate and circulation effects: theory and application to the European summer climate

Science.gov (United States)

Kröner, Nico; Kotlarski, Sven; Fischer, Erich; Lüthi, Daniel; Zubler, Elias; Schär, Christoph

2017-05-01

Climate models robustly project a strong overall summer warming across Europe showing a characteristic north-south gradient with enhanced warming and drying in southern Europe. However, the processes that are responsible for this pattern are not fully understood. We here employ an extended surrogate or pseudo-warming approach to disentangle the contribution of different mechanisms to this response pattern. The basic idea of the surrogate technique is to use a regional climate model and apply a large-scale warming to the lateral boundary conditions of a present-day reference simulation, while maintaining the relative humidity (and thus implicitly increasing the specific moisture content). In comparison to previous studies, our approach includes two important extensions: first, different vertical warming profiles are applied in order to separate the effects of a mean warming from lapse-rate effects. Second, a twin-design is used, in which the climate change signals are not only added to present-day conditions, but also subtracted from a scenario experiment. We demonstrate that these extensions provide an elegant way to separate the full climate change signal into contributions from large-scale thermodynamic (TD), lapse-rate (LR), and circulation and other remaining effects (CO). The latter in particular include changes in land-ocean contrast and spatial variations of the SST warming patterns. We find that the TD effect yields a large-scale warming across Europe with no distinct latitudinal gradient. The LR effect, which is quantified for the first time in our study, leads to a stronger warming and some drying in southern Europe. It explains about 50 % of the warming amplification over the Iberian Peninsula, thus demonstrating the important role of lapse-rate changes. The effect is linked to an extending Hadley circulation. The CO effect as inherited from the driving GCM is shown to further amplify the north-south temperature change gradient. In terms of mean summer

The ratio of land to ocean temperature change under global warming

Energy Technology Data Exchange (ETDEWEB)

Boer, G.J. [Environment Canada, Canadian Centre for Climate Modelling and Analysis, c/o University of Victoria, PO Box 1700, Victoria, BC (Canada)

2011-12-15

The result in climate simulations, supported in the observation-based record, is that the ratio {phi}= T{sub L}/T{sub O} of land-average to ocean-average temperature change is greater than one and varies comparatively modestly as climate changes. This is investigated in results from the CMIP3 data archive of climate change simulations following the B1 and more strongly forced A1B scenarios as well as in 2 x CO{sub 2} integrations. The associated precipitation ratio {psi}=P{sub L}/P{sub O} is also considered briefly. The behaviour of {phi} is analyzed in terms of a forcing-response view of the energy balance over land and ocean regions. The analysis indicates that the value of {phi}> 1 is not maintained by separate local balances over land and ocean but by an energetic balance that also involves a change in transport between the regions. The transport change does not restrain the land warming by exporting energy to the ocean region but, rather, the reverse. The anomalous transport is from the ocean to the land region even though the ocean warms less than the land does. Feedbacks in the ocean region, especially in the equatorial Pacific, do not sufficiently counteract the forcing and the result is an excess of energy that is transported to the land. The land warms in order to radiate away both the energy from the forcing over land but also the extra energy imported from the ocean region, thereby maintaining {phi} > 1. This situation can be understood to parallel the SST-forced case in model studies where {phi} > 1 despite the forcing being confined to the ocean area. The climate system is effective in redistributing forcing so that it is the local feedbacks, rather than the pattern of the forcing, that determine the temperature response. Land and ocean averaged quantities and budgets behave in a consistent manner to provide a simplified representation of the changes in temperature and energetic processes that are occurring. The geographical distributions of the terms

Relative effects of precipitation variability and warming on tallgrass prairie ecosystem function

Directory of Open Access Journals (Sweden)

P. A. Fay

2011-10-01

Full Text Available Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenarios predict increasing precipitation variability and temperature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual rainfall variability, and warming. We present results from an experiment applying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ~50–200% interannual variability in plant growth and aboveground net primary productivity (ANPP, leaf carbon assimilation (A_CO2, and soil CO₂ efflux (J_CO2 despite only ~40% variation in mean volumetric soil water content (0–15 cm, Θ₁₅. Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Differences between years in Θ₁₅ explained the greatest portion (14–52% of the variation in these processes. Experimentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture variation and reduced Θ₁₅ by 15%, causing most ecosystem processes to decrease 8–40% in some or all years with increased rainfall variability compared to ambient rainfall timing, suggesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, particularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter J_CO2, and reduced summer J_CO2 and forb ANPP, suggesting that the effects of warming differed in cooler versus warmer parts of the year. We conclude that (1 major ecosystem processes in this grassland may be substantially altered by predicted changes in

Decreasing Asian summer monsoon intensity after 1860 AD in the global warming epoch

Energy Technology Data Exchange (ETDEWEB)

Xu, Hai [Institute of Earth Environment, Chinese Academy of Sciences, State Key Laboratory of Loess and Quaternary Geology, Xi' an, Shaanxi Province (China); Hong, Yetang; Hong, Bin [Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Environmental Geochemistry, Guiyang (China)

2012-10-15

The trend of the Indian summer monsoon (ISM) intensity and its nature during the past 100 and 200 years still remain unclear. In this study we reconstructed the ISM intensity during the past 270 years from tree ring {delta}{sup 18}O at Hongyuan, eastern edge of the Tibet Plateau. The monsoon failures inferred from {delta}{sup 18}O{sub tree} {sub ring} correlate well with those recorded in ice cores, speleothem, and historical literature sources. 22.6, 59.0, and 110.9-years frequency components in the Hongyuan {delta}{sup 18}O{sub tree} {sub ring} series, which may be the responses to solar activities, synchronize well with those recorded in other ISM indices. A notable feature of the reconstructed ISM intensity is the gradually decreasing trend from about 1860 to the present, which is inversely related to the increasing temperature trend contemporaneously. Such ''decreasing ISM intensity-increasing temperature'' tendency can also be supported by ice core records and meteorological records over a wide geographic extension. The decrease in sea surface temperature gradient between tropical and north Indian Ocean, and the decrease in land-sea thermal contrast between tropical Indian Ocean and ''Indian sub-continent-western Himalaya'' are possibly responsible for the observed decreasing ISM trend. (orig.)

Impacts of 1, 1.5, and 2 Degree Warming on Arctic Terrestrial Snow and Sea Ice

Science.gov (United States)

Derksen, C.; Mudryk, L.; Howell, S.; Flato, G. M.; Fyfe, J. C.; Gillett, N. P.; Sigmond, M.; Kushner, P. J.; Dawson, J.; Zwiers, F. W.; Lemmen, D.; Duguay, C. R.; Zhang, X.; Fletcher, C. G.; Dery, S. J.

2017-12-01

The 2015 Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC) established the global temperature goal of "holding the increase in the global average temperature to below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels." In this study, we utilize multiple gridded snow and sea ice products (satellite retrievals; assimilation systems; physical models driven by reanalyses) and ensembles of climate model simulations to determine the impacts of observed warming, and project the relative impacts of the UNFCC future warming targets on Arctic seasonal terrestrial snow and sea ice cover. Observed changes during the satellite era represent the response to approximately 1°C of global warming. Consistent with other studies, analysis of the observational record (1970's to present) identifies changes including a shorter snow cover duration (due to later snow onset and earlier snow melt), significant reductions in spring snow cover and summer sea ice extent, and the loss of a large proportion of multi-year sea ice. The spatial patterns of observed snow and sea ice loss are coherent across adjacent terrestrial/marine regions. There are strong pattern correlations between snow and temperature trends, with weaker association between sea ice and temperature due to the additional influence of dynamical effects such wind-driven redistribution of sea ice. Climate model simulations from the Coupled Model Inter-comparison Project Phase 5(CMIP-5) multi-model ensemble, large initial condition ensembles of the Community Earth System Model (CESM) and Canadian Earth System Model (CanESM2) , and warming stabilization simulations from CESM were used to identify changes in snow and ice under further increases to 1.5°C and 2°C warming. The model projections indicate these levels of warming will be reached over the coming 2-4 decades. Warming to 1.5°C results in an increase in the

Extreme High-Temperature Events Over East Asia in 1.5°C and 2°C Warmer Futures: Analysis of NCAR CESM Low-Warming Experiments

Science.gov (United States)

Li, Donghuan; Zhou, Tianjun; Zou, Liwei; Zhang, Wenxia; Zhang, Lixia

2018-02-01

Extreme high-temperature events have large socioeconomic and human health impacts. East Asia (EA) is a populous region, and it is crucial to assess the changes in extreme high-temperature events in this region under different climate change scenarios. The Community Earth System Model low-warming experiment data were applied to investigate the changes in the mean and extreme high temperatures in EA under 1.5°C and 2°C warming conditions above preindustrial levels. The results show that the magnitude of warming in EA is approximately 0.2°C higher than the global mean. Most populous subregions, including eastern China, the Korean Peninsula, and Japan, will see more intense, more frequent, and longer-lasting extreme temperature events under 1.5°C and 2°C warming. The 0.5°C lower warming will help avoid 35%-46% of the increases in extreme high-temperature events in terms of intensity, frequency, and duration in EA with maximal avoidance values (37%-49%) occurring in Mongolia. Thus, it is beneficial for EA to limit the warming target to 1.5°C rather than 2°C.

The Response of a Branch of Puget Sound, Washington to the 2014 North Pacific Warm Anomaly

Science.gov (United States)

Mickett, J.; Newton, J.; Devol, A.; Krembs, C.; Ruef, W.

2016-02-01

The flow of the unprecedentedly-warm upper-ocean North Pacific "Blob" water into Puget Sound, Washington, caused local extreme water property anomalies that extended from the arrival of the water inshore in the fall of 2014 through 2015. Here we report on moored and seaplane observations from Hood Canal, a branch of Puget Sound, where temperature was more than 2σ above climatology for much of the year with maximum temperature anomalies at depth and at the surface +2.5 °C and +7 °C respectively. The low density of the oceanic warm "Blob" water resulted in weak deep water flushing in Hood Canal in the fall of 2014, which combined with a lack of wintertime flushing to result in anomalously-low dissolved oxygen (DO) concentrations at depth. Late-summer 2015 DO values were the lowest in a decade of mooring observations and more than 2σ below climatology. The anomalously low density of the deep basin water allowed a very early onset of the annually-occurring, late-summer intrusion, which first entered Hood Canal at the end of July compared to the usual arrival in early to mid-September. In late August this intrusion conspired with an early fall storm to lift the very low DO deep water to surface at the south end of Hood Canal, causing a significant fish kill event.

Plants, birds and butterflies: short-term responses of species communities to climate warming vary by taxon and with altitude.

Science.gov (United States)

Roth, Tobias; Plattner, Matthias; Amrhein, Valentin

2014-01-01

As a consequence of climate warming, species usually shift their distribution towards higher latitudes or altitudes. Yet, it is unclear how different taxonomic groups may respond to climate warming over larger altitudinal ranges. Here, we used data from the national biodiversity monitoring program of Switzerland, collected over an altitudinal range of 2500 m. Within the short period of eight years (2003-2010), we found significant shifts in communities of vascular plants, butterflies and birds. At low altitudes, communities of all species groups changed towards warm-dwelling species, corresponding to an average uphill shift of 8 m, 38 m and 42 m in plant, butterfly and bird communities, respectively. However, rates of community changes decreased with altitude in plants and butterflies, while bird communities changed towards warm-dwelling species at all altitudes. We found no decrease in community variation with respect to temperature niches of species, suggesting that climate warming has not led to more homogenous communities. The different community changes depending on altitude could not be explained by different changes of air temperatures, since during the 16 years between 1995 and 2010, summer temperatures in Switzerland rose by about 0.07°C per year at all altitudes. We discuss that land-use changes or increased disturbances may have prevented alpine plant and butterfly communities from changing towards warm-dwelling species. However, the findings are also consistent with the hypothesis that unlike birds, many alpine plant species in a warming climate could find suitable habitats within just a few metres, due to the highly varied surface of alpine landscapes. Our results may thus support the idea that for plants and butterflies and on a short temporal scale, alpine landscapes are safer places than lowlands in a warming world.

Temperature dependence of mode conversion in warm, unmagnetized plasmas with a linear density profile

Energy Technology Data Exchange (ETDEWEB)

Yu, Dae Jung; Lee, Dong-Hun [School of Space Research, Kyung Hee University, Yongin (Korea, Republic of); Kim, Kihong [Division of Energy Systems Research, Ajou University, Suwon (Korea, Republic of)

2013-06-15

We study theoretically the linear mode conversion between electromagnetic waves and Langmuir waves in warm, stratified, and unmagnetized plasmas, using a numerically precise calculation based on the invariant imbedding method. We verify that the principle of reciprocity for the forward and backward mode conversion coefficients holds precisely regardless of temperature. We also find that the temperature dependence of the mode conversion coefficient is substantially stronger than that previously reported. Depending on the wave frequency and the incident angle, the mode conversion coefficient is found to increase or decrease with the increase of temperature.

An investigation of the effects from a urethral warming system on temperature distributions during cryoablation treatment of the prostate: a phantom study.

Science.gov (United States)

Favazza, C P; Gorny, K R; King, D M; Rossman, P J; Felmlee, J P; Woodrum, D A; Mynderse, L A

2014-08-01

Introduction of urethral warmers to aid cryosurgery in the prostate has significantly reduced the incidence of urethral sloughing; however, the incidence rate still remains as high as 15%. Furthermore, urethral warmers have been associated with an increase of cancer recurrence rates. Here, we report results from our phantom-based investigation to determine the impact of a urethral warmer on temperature distributions around cryoneedles during cryosurgery. Cryoablation treatments were simulated in a tissue mimicking phantom containing a urethral warming catheter. Four different configurations of cryoneedles relative to urethral warming catheter were investigated. For each configuration, the freeze-thaw cycles were repeated with and without the urethral warming system activated. Temperature histories were recorded at various pre-arranged positions relative to the cryoneedles and urethral warming catheter. In all configurations, the urethral warming system was effective at maintaining sub-lethal temperatures at the simulated surface of the urethra. The warmer action, however, was additionally demonstrated to potentially negatively impact treatment lethality in the target zone by elevating minimal temperatures to sub-lethal levels. In all needle configurations, rates of freezing and thawing were not significantly affected by the use of the urethral warmer. The results indicate that the urethral warming system can protect urethral tissue during cryoablation therapy with cryoneedles placed as close as 5mm to the surface of the urethra. Using a urethral warming system and placing multiple cryoneedles within 1cm of each other delivers lethal cooling at least 5mm from the urethral surface while sparing urethral tissue. Copyright © 2014 Elsevier Inc. All rights reserved.

Water temperature effects from simulated changes to dam operations and structures in the Middle and South Santiam Rivers, Oregon

Science.gov (United States)

Buccola, Norman L.

2017-05-31

Green Peter and Foster Dams on the Middle and South Santiam Rivers, Oregon, have altered the annual downstream water temperature profile (cycle). Operation of the dams has resulted in cooler summer releases and warmer autumn releases relative to pre-dam conditions, and that alteration can hinder recovery of various life stages of threatened spring-run Chinook salmon (Oncorhyncus tshawytscha) and winter steelhead (O. mykiss). Lake level management and the use of multiple outlets from varying depths at the dams can enable the maintenance of a temperature regime more closely resembling that in which the fish evolved by releasing warm surface water during summer and cooler, deeper water in the autumn. At Green Peter and Foster Dams, the outlet configuration is such that temperature control is often limited by hydropower production at the dams. Previously calibrated CE-QUAL-W2 water temperature models of Green Peter and Foster Lakes were used to simulate the downstream thermal effects from hypothetical structures and modified operations at the dams. Scenarios with no minimum power production requirements allowed some releases through shallower and deeper outlets (summer and autumn) to achieve better temperature control throughout the year and less year-to-year variability in autumn release temperatures. Scenarios including a hypothetical outlet floating 1 meter below the lake surface resulted in greater ability to release warm water during summer compared to existing structures. Later in Autumn (October 15–December 31), a limited amount of temperature control was realized downstream from Foster Dam by scenarios limited to operational changes with existing structures, resulting in 15-day averages within 1.0 degree Celsius of current operations.

Western US high June 2015 temperatures and their relation to global warming and soil moisture

Science.gov (United States)

Philip, Sjoukje Y.; Kew, Sarah F.; Hauser, Mathias; Guillod, Benoit P.; Teuling, Adriaan J.; Whan, Kirien; Uhe, Peter; Oldenborgh, Geert Jan van

2018-04-01

The Western US states Washington (WA), Oregon (OR) and California (CA) experienced extremely high temperatures in June 2015. The temperature anomalies were so extreme that they cannot be explained with global warming alone. We investigate the hypothesis that soil moisture played an important role as well. We use a land surface model and a large ensemble from the weather@home modelling effort to investigate the coupling between soil moisture and temperature in a warming world. Both models show that May was anomalously dry, satisfying a prerequisite for the extreme heat wave, and they indicate that WA and OR are in a wet-to-dry transitional soil moisture regime. We use two different land surface-atmosphere coupling metrics to show that there was strong coupling between temperature, latent heat flux and the effect of soil moisture deficits on the energy balance in June 2015 in WA and OR. June temperature anomalies conditioned on wet/dry conditions show that both the mean and extreme temperatures become hotter for dry soils, especially in WA and OR. Fitting a Gaussian model to temperatures using soil moisture as a covariate shows that the June 2015 temperature values fit well in the extrapolated empirical temperature/drought lines. The high temperature anomalies in WA and OR are thus to be expected, given the dry soil moisture conditions and that those regions are in the transition from a wet to a dry regime. CA is already in the dry regime and therefore the necessity of taking soil moisture into account is of lower importance.

Projected Temperature-Related Years of Life Lost From Stroke Due To Global Warming in a Temperate Climate City, Asia: Disease Burden Caused by Future Climate Change.

Science.gov (United States)

Li, Guoxing; Guo, Qun; Liu, Yang; Li, Yixue; Pan, Xiaochuan

2018-04-01

Global warming has attracted worldwide attention. Numerous studies have indicated that stroke is associated with temperature; however, few studies are available on the projections of the burden of stroke attributable to future climate change. We aimed to investigate the future trends of stroke years of life lost (YLL) associated with global warming. We collected death records to examine YLL in Tianjin, China, from 2006 to 2011. We fitted a standard time-series Poisson regression model after controlling for trends, day of the week, relative humidity, and air pollution. We estimated temperature-YLL associations with a distributed lag nonlinear model. These models were then applied to the local climate projections to estimate temperature-related YLL in the 2050s and 2070s. We projected temperature-related YLL from stroke in Tianjin under 19 global-scale climate models and 3 different greenhouse gas emission scenarios. The results showed a slight decrease in YLL with percent decreases of 0.85%, 0.97%, and 1.02% in the 2050s and 0.94%, 1.02%, and 0.91% in the 2070s for the 3 scenarios, respectively. The increases in heat-related annual YLL and the decreases in cold-related YLL under the high emission scenario were the strongest. The monthly analysis showed that the most significant increase occurred in the summer months, particularly in August, with percent changes >150% in the 2050s and up to 300% in the 2070s. Future changes in climate are likely to lead to an increase in heat-related YLL, and this increase will not be offset by adaptation under both medium emission and high emission scenarios. Health protections from hot weather will become increasingly necessary, and measures to reduce cold effects will also remain important. © 2018 American Heart Association, Inc.

Does the correlation between solar cycle lengths and Northern Hemisphere land temperatures rule out any significant global warming from greenhouse gases?

DEFF Research Database (Denmark)

Laut, Peter; Gundermann, Jesper

1998-01-01

Since the discovery of a striking correlation between solar cycle lengths and Northern Hemisphere land temperatures there have been widespread speculations as to whether these findings would rule out any significant contributions to global warming from the enhanced concentrations of greenhouse...... gases. The present analysis shows that a similar degree of correlation is obtained when testing the solar data against a couple of fictitious temperature series representing different global warming trends. Therefore, the correlation cannot be used to estimate the magnitude of a possible contribution...... to global warming from human activities, nor to rule out a sizable contribution from that source....

Extreme temperatures in Southeast Asia caused by El Niño and worsened by global warming

Science.gov (United States)

Thirumalai, Kaustubh; DiNezio, Pedro N.; Okumura, Yuko; Deser, Clara

2017-01-01

In April 2016, southeast Asia experienced surface air temperatures (SATs) that surpassed national records, exacerbated energy consumption, disrupted agriculture and caused severe human discomfort. Here we show using observations and an ensemble of global warming simulations the combined impact of the El Niño/Southern Oscillation (ENSO) phenomenon and long-term warming on regional SAT extremes. We find a robust relationship between ENSO and southeast Asian SATs wherein virtually all April extremes occur during El Niño years. We then quantify the relative contributions of long-term warming and the 2015–16 El Niño to the extreme April 2016 SATs. The results indicate that global warming increases the likelihood of record-breaking April extremes where we estimate that 29% of the 2016 anomaly was caused by warming and 49% by El Niño. These post-Niño Aprils can potentially be anticipated a few months in advance, and thus, help societies prepare for the projected continued increases in extremes. PMID:28585927

Artists Paint ... Summer: Grade 2

Science.gov (United States)

Herberholz, Barbara

2012-01-01

A humid summer haze covers the River Seine and the grassy bank where young men and boys go swimming on Sunday. Everything seems so quiet, still, and very hot. They wear hats to protect them from the hot sun. The artist Georges Seurat used warm tones to give viewers the feeling of the hot sun. Seurat was trying to catch the dazzle of hot sunlight…

Measuring the temperature history of isochorically heated warm dense metals

Science.gov (United States)

McGuffey, Chris; Kim, J.; Park, J.; Moody, J.; Emig, J.; Heeter, B.; Dozieres, M.; Beg, Fn; McLean, Hs

2017-10-01

A pump-probe platform has been designed for soft X-ray absorption spectroscopy near edge structure measurements in isochorically heated Al or Cu samples with temperature of 10s to 100s of eV. The method is compatible with dual picosecond-class laser systems and may be used to measure the temperature of the sample heated directly by the pump laser or by a laser-driven proton beam Knowledge of the temperature history of warm dense samples will aid equation of state measurements. First, various low- to mid-Z targets were evaluated for their suitability as continuum X-ray backlighters over the range 200-1800 eV using a 10 J picosecond-class laser with relativistic peak intensity Alloys were found to be more suitable than single-element backlighters. Second, the heated sample package was designed with consideration of target thickness and tamp layers using atomic physics codes. The results of the first demonstration attempts will be presented. This work was supported by the U.S. DOE under Contract No. DE-SC0014600.

What to eat in a warming world: do increased temperatures necessitate hazardous duty pay?

Science.gov (United States)

Hall, L. Embere; Chalfoun, Anna D.

2018-01-01

Contemporary climate change affects nearly all biomes, causing shifts in animal distributions and resource availability. Changes in resource selection may allow individuals to offset climatic stress, thereby providing a mechanism for persistence amidst warming conditions. Whereas the role of predation risk in food choice has been studied broadly, the extent to which individuals respond to thermoregulatory risk by changing resource preferences is unclear. We addressed whether individuals compensated for temperature-related reductions in foraging time by altering forage preferences, using the American pika (Ochotona princeps) as a model species. We tested two hypotheses: (1) food-quality hypothesis—individuals exposed to temperature extremes should select higher-quality vegetation in return for accepting a physiologically riskier feeding situation; and (2) food-availability hypothesis—individuals exposed to temperature extremes should prioritize foraging quickly, thereby decreasing selection for higher-quality food. We quantified the composition and quality (% moisture, % nitrogen, and fiber content) of available and harvested vegetation, and deployed a network of temperature sensors to measure in situ conditions for 30 individuals, during July–Sept., 2015. Individuals exposed to more extreme daytime temperatures showed increased selection for high-nitrogen and for low-fiber vegetation, demonstrating strong support for the food-quality hypothesis. By contrast, pikas that experienced warmer conditions did not reduce selection for any of the three vegetation-quality metrics, as predicted by the food-availability hypothesis. By shifting resource-selection patterns, temperature-limited animals may be able to proximately buffer some of the negative effects associated with rapidly warming environments, provided that sufficient resources remain on the landscape.

Design and performance of combined infrared canopy and belowground warming in the B4WarmED (Boreal Forest Warming at an Ecotone in Danger) experiment.

Science.gov (United States)

Rich, Roy L; Stefanski, Artur; Montgomery, Rebecca A; Hobbie, Sarah E; Kimball, Bruce A; Reich, Peter B

2015-06-01

Conducting manipulative climate change experiments in complex vegetation is challenging, given considerable temporal and spatial heterogeneity. One specific challenge involves warming of both plants and soils to depth. We describe the design and performance of an open-air warming experiment called Boreal Forest Warming at an Ecotone in Danger (B4WarmED) that addresses the potential for projected climate warming to alter tree function, species composition, and ecosystem processes at the boreal-temperate ecotone. The experiment includes two forested sites in northern Minnesota, USA, with plots in both open (recently clear-cut) and closed canopy habitats, where seedlings of 11 tree species were planted into native ground vegetation. Treatments include three target levels of plant canopy and soil warming (ambient, +1.7°C, +3.4°C). Warming was achieved by independent feedback control of voltage input to aboveground infrared heaters and belowground buried resistance heating cables in each of 72-7.0 m(2) plots. The treatments emulated patterns of observed diurnal, seasonal, and annual temperatures but with superimposed warming. For the 2009 to 2011 field seasons, we achieved temperature elevations near our targets with growing season overall mean differences (∆Tbelow ) of +1.84°C and +3.66°C at 10 cm soil depth and (∆T(above) ) of +1.82°C and +3.45°C for the plant canopies. We also achieved measured soil warming to at least 1 m depth. Aboveground treatment stability and control were better during nighttime than daytime and in closed vs. open canopy sites in part due to calmer conditions. Heating efficacy in open canopy areas was reduced with increasing canopy complexity and size. Results of this study suggest the warming approach is scalable: it should work well in small-statured vegetation such as grasslands, desert, agricultural crops, and tree saplings (<5 m tall). © 2015 John Wiley & Sons Ltd.

Long-term European temperature variations between 1525 and the present

International Nuclear Information System (INIS)

Weber, G.R.

1994-01-01

Long-term European temperature records are analyzed between 1525 and the present. It is found that the warmest periods occurred around the middle of this century, whereas the coldest periods generally occurred around the middle and the end of the last century. Urban warming may have occurred in the 19th century, causing urban areas to warm relative to rural areas and smaller towns between 1800 and 1900. The magnitude of natural climatic variability was determined. Trends were calculated for various time intervals. There was general warming between late 19th century and the present, but general cooling between the late 18th century and late 19th century. In some longer-term records, there was cooling between the 16th and the late 19th century. The largest warming occurred in the 1900s and in the 1930s. There has been a pronounced seasonal variation in trends of the last 200 years, with warming being centered in late fall to early spring, whereas the summer half of the year either did not warm or even cooled. European temperatures in the last decades are significantly above longer-term averages. However, they are much below estimates of modeled greenhouse warming which might have occurred in the last decades. Those differences cannot plausibly be explained by natural climatic variability. 43 refs., 5 figs., 10 tabs

Wheat production in Bangladesh: its future in the light of global warming

Science.gov (United States)

Hossain, Akbar; Teixeira da Silva, Jaime A.

2012-01-01

Background and aims The most fundamental activity of the people of Bangladesh is agriculture. Modelling projections for Bangladesh indicate that warmer temperatures linked to climate change will severely reduce the growth of various winter crops (wheat, boro rice, potato and winter vegetables) in the north and central parts. In summer, crops in south-eastern parts of the country are at risk from increased flooding as sea levels increase. Key facts Wheat is one of the most important winter crops and is temperature sensitive and the second most important grain crop after rice. In this review, we provide an up-to-date and detailed account of wheat research of Bangladesh and the impact that global warming may have on agriculture, especially wheat production. Although flooding is not of major importance or consequence to the wheat crop at present, some perspectives are provided on this stress since wheat is flood sensitive and the incidence of flooding is likely to increase. Projections This information and projections will allow wheat breeders to devise new breeding programmes to attempt to mitigate future global warming. We discuss what this implies for food security in the broader context of South Asia. PMID:23304431

Global Warming: A Reduced Threat?.

Science.gov (United States)

Michaels, Patrick J.; Stooksbury, David E.

1992-10-01

One popular and apocalyptic vision of the world influenced by increasing concentrations of infrared-absorbing trace gases is that of ecological disaster brought about by rapidly rising temperatures, sea level, and evaporation rates. This vision developed from a suite of climate models that have since considerably changed in both their dynamics and their estimates of prospective warming. Observed temperatures indicate that much more warming should already have taken place than predicted by earlier models in the Northern Hemisphere, and that night, rather than day, readings in that hemisphere show a relative warming. A high-latitude polar-night warming or a general night warming could be either benign or beneficial. A large number of plant species show both increased growth and greater water-use efficiency under enhanced carbon dioxide.An extensive body of evidence now indicates that anthropo-generated sulfate emissions are mitigating some of the warming, and that increased cloudiness as a result of these emissions will further enhance night, rather than day, warming. The sulfate emissions, though, are not sufficient to explain all of the night warming. However, the sensitivity of climate to anthropogenerated aerosols, and the general lack of previously predicted warming, could drastically alter the debate on global warming in favor of less expensive policies.

The impact of global warming on germination and seedling emergence in Alliaria petiolata, a woodland species with dormancy loss dependent on low temperature.

Science.gov (United States)

Footitt, S; Huang, Z; Ölcer-Footitt, H; Clay, H; Finch-Savage, W E

2018-03-23

The impact of global warming on seed dormancy loss and germination was investigated in Alliaria petiolata (garlic mustard), a common woodland/hedgerow plant in Eurasia, considered invasive in North America. Increased temperature may have serious implications, since seeds of this species germinate and emerge at low temperatures early in spring to establish and grow before canopy development of competing species. Dormancy was evaluated in seeds buried in field soils. Seedling emergence was also investigated in the field, and in a thermogradient tunnel under global warming scenarios representing predicted UK air temperatures through to 2080. Dormancy was simple, and its relief required the accumulation of low temperature chilling time. Under a global warming scenario, dormancy relief and seedling emergence declined and seed mortality increased as soil temperature increased along a thermal gradient. Seedling emergence advanced with soil temperature, peaking 8 days earlier under 2080 conditions. The results indicate that as mean temperature increases due to global warming, the chilling requirement for dormancy relief may not be fully satisfied, but seedling emergence will continue from low dormancy seeds in the population. Adaptation resulting from selection of this low dormancy proportion is likely to reduce the overall population chilling requirement. Seedling emergence is also likely to keep pace with the advancement of biological spring, enabling A. petiolata to maintain its strategy of establishment before the woodland canopy closes. However, this potential for adaptation may be countered by increased seed mortality in the seed bank as soils warm. © 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Abrupt warming of the Red Sea

KAUST Repository

Raitsos, D. E.

2011-07-19

Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

Abrupt warming of the Red Sea

Science.gov (United States)

Raitsos, D. E.; Hoteit, I.; Prihartato, P. K.; Chronis, T.; Triantafyllou, G.; Abualnaja, Y.

2011-07-01

Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

Testing the Metabolic Theory of Ecology with marine bacteria: Different temperature sensitivity of major phylogenetic groups during the spring phytoplankton bloom

KAUST Repository

Arandia-Gorostidi, Nestor

2017-08-24

Although temperature is a key driver of bacterioplankton metabolism, the effect of ocean warming on different bacterial phylogenetic groups remains unclear. Here, we conducted monthly short-term incubations with natural coastal bacterial communities over an annual cycle to test the effect of experimental temperature on the growth rates and carrying capacities of four phylogenetic groups: SAR11, Rhodobacteraceae, Gammaproteobacteria and Bacteroidetes. SAR11 was the most abundant group year-round as analysed by CARD-FISH, with maximum abundances in summer, while the other taxa peaked in spring. All groups, including SAR11, showed high temperature-sensitivity of growth rates and/or carrying capacities in spring, under phytoplankton bloom or post-bloom conditions. In that season, Rhodobacteraceae showed the strongest temperature response in growth rates, estimated here as activation energy (E, 1.43 eV), suggesting an advantage to outcompete other groups under warmer conditions. In summer E values were in general lower than 0.65 eV, the value predicted by the Metabolic Theory of Ecology (MTE). Contrary to MTE predictions, carrying capacity tended to increase with warming for all bacterial groups. Our analysis confirms that resource availability is key when addressing the temperature response of heterotrophic bacterioplankton. We further show that even under nutrient-sufficient conditions, warming differentially affected distinct bacterioplankton taxa. This article is protected by copyright. All rights reserved.

Modeling the Warming Impact of Urban Land Expansion on Hot Weather Using the Weather Research and Forecasting Model: A Case Study of Beijing, China

Science.gov (United States)

Liu, Xiaojuan; Tian, Guangjin; Feng, Jinming; Ma, Bingran; Wang, Jun; Kong, Lingqiang

2018-06-01

The impacts of three periods of urban land expansion during 1990-2010 on near-surface air temperature in summer in Beijing were simulated in this study, and then the interrelation between heat waves and urban warming was assessed. We ran the sensitivity tests using the mesoscaleWeather Research and Forecasting model coupled with a single urban canopy model, as well as high-resolution land cover data. The warming area expanded approximately at the same scale as the urban land expansion. The average regional warming induced by urban expansion increased but the warming speed declined slightly during 2000-2010. The smallest warming occurred at noon and then increased gradually in the afternoon before peaking at around 2000 LST—the time of sunset. In the daytime, urban warming was primarily caused by the decrease in latent heat flux at the urban surface. Urbanization led to more ground heat flux during the day and then more release at night, which resulted in nocturnal warming. Urban warming at night was higher than that in the day, although the nighttime increment in sensible heat flux was smaller. This was because the shallower planetary boundary layer at night reduced the release efficiency of near-surface heat. The simulated results also suggested that heat waves or high temperature weather enhanced urban warming intensity at night. Heat waves caused more heat to be stored in the surface during the day, greater heat released at night, and thus higher nighttime warming. Our results demonstrate a positive feedback effect between urban warming and heat waves in urban areas.

New climatic targets against global warming: will the maximum 2 °C temperature rise affect estuarine benthic communities?

Science.gov (United States)

Crespo, Daniel; Grilo, Tiago Fernandes; Baptista, Joana; Coelho, João Pedro; Lillebø, Ana Isabel; Cássio, Fernanda; Fernandes, Isabel; Pascoal, Cláudia; Pardal, Miguel Ângelo; Dolbeth, Marina

2017-06-20

The Paris Agreement signed by 195 countries in 2015 sets out a global action plan to avoid dangerous climate change by limiting global warming to remain below 2 °C. Under that premise, in situ experiments were run to test the effects of 2 °C temperature increase on the benthic communities in a seagrass bed and adjacent bare sediment, from a temperate European estuary. Temperature was artificially increased in situ and diversity and ecosystem functioning components measured after 10 and 30 days. Despite some warmness effects on the analysed components, significant impacts were not verified on macro and microfauna structure, bioturbation or in the fluxes of nutrients. The effect of site/habitat seemed more important than the effects of the warmness, with the seagrass habitat providing more homogenous results and being less impacted by warmness than the adjacent bare sediment. The results reinforce that most ecological responses to global changes are context dependent and that ecosystem stability depends not only on biological diversity but also on the availability of different habitats and niches, highlighting the role of coastal wetlands. In the context of the Paris Agreement it seems that estuarine benthic ecosystems will be able to cope if global warming remains below 2 °C.

Rayleigh lidar observations of enhanced stratopause temperature over Gadanki (13.5° N, 79.2° E) during major stratospheric warming in 2006

Science.gov (United States)

Sridharan, S.; Sathishkumar, S.; Raghunath, K.

2009-01-01

Rayleigh lidar observations of temperature structure and gravity wave activity were carried out at Gadanki (13.5° N, 79.2° E) during January-February 2006. A major stratospheric warming event occurred at high latitude during the end of January and early February. There was a sudden enhancement in the stratopause temperature over Gadanki coinciding with the date of onset of the major stratospheric warming event which occurred at high latitudes. The temperature enhancement persisted even after the end of the high latitude major warming event. During the same time, the UKMO (United Kingdom Meteorological Office) zonal mean temperature showed a similar warming episode at 10° N and cooling episode at 60° N around the region of stratopause. This could be due to ascending (descending) motions at high (low) latitudes above the critical level of planetary waves, where there was no planetary wave flux. The time variation of the gravity wave potential energy computed from the temperature perturbations over Gadanki shows variabilities at planetary wave periods, suggesting a non-linear interaction between gravity waves and planetary waves. The space-time analysis of UKMO temperature data at high and low latitudes shows the presence of similar periodicities of planetary wave of zonal wavenumber 1.

Rayleigh lidar observations of enhanced stratopause temperature over Gadanki (13.5° N, 79.2° E during major stratospheric warming in 2006

Directory of Open Access Journals (Sweden)

S. Sridharan

2009-01-01

Full Text Available Rayleigh lidar observations of temperature structure and gravity wave activity were carried out at Gadanki (13.5° N, 79.2° E during January–February 2006. A major stratospheric warming event occurred at high latitude during the end of January and early February. There was a sudden enhancement in the stratopause temperature over Gadanki coinciding with the date of onset of the major stratospheric warming event which occurred at high latitudes. The temperature enhancement persisted even after the end of the high latitude major warming event. During the same time, the UKMO (United Kingdom Meteorological Office zonal mean temperature showed a similar warming episode at 10° N and cooling episode at 60° N around the region of stratopause. This could be due to ascending (descending motions at high (low latitudes above the critical level of planetary waves, where there was no planetary wave flux. The time variation of the gravity wave potential energy computed from the temperature perturbations over Gadanki shows variabilities at planetary wave periods, suggesting a non-linear interaction between gravity waves and planetary waves. The space-time analysis of UKMO temperature data at high and low latitudes shows the presence of similar periodicities of planetary wave of zonal wavenumber 1.

Peatland Carbon Dynamics in Alaska During Past Warm Climates

Science.gov (United States)

Yu, Z.; Cleary, K.; Massa, C.; Hunt, S. J.; Klein, E. S.; Loisel, J.

2013-12-01

Peatlands represent a large belowground carbon (C) pool in the biosphere. However, how peatland C sequestration capacity varies with changes in climate and climate-induced disturbance is still poorly understood and debated. Here we summarize results from Alaskan peatlands to document how peat C accumulation has responded to past warm climate intervals. We find that the greatest C accumulation rates at sites from the Kenai Peninsula to the North Slope occurred during the Holocene thermal maximum (HTM) in the early Holocene. This time period also corresponds with explosive formation and expansion of new peatlands on the landscape across Alaska. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or sandy deposits. During the Medieval Climate Anomaly (MCA) around 1000-500 years ago, several peatlands in Alaska show high rates of C accumulation when compared to the period before the MCA during the Neoglacial or the following Little Ice Age period. Altogether, our results indicate that the Alaskan landscape was very different during the last 10,000 years and that peatlands can rapidly accumulate C under warm climatic conditions. We speculate that warmth-stimulated increase in plant production surpasses increase in peat decomposition during the early Holocene, and potentially also during the MCA. Other factors that might have contributed to rapid peat accumulation during the early Holocene include increased summer sunlight, lowered sea levels, and decreased sea-ice cover/duration. Summer insolation was ca. 8% higher than today during the early Holocene due to orbital variations, which likely promoted plant productivity by increasing growing seasons sunlight. Furthermore, lower sea levels and exposed shallow continental shelves in the Beaufort Sea (Arctic Ocean) would have made the present-day Arctic Coastal Plain more continental, with warmer summers

Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island lakes (Nunavut, Canada) and reconstruction of summer water temperature

Energy Technology Data Exchange (ETDEWEB)

Joynt, E. H. III; Wolfe, A. P. [Colorado Univ., Inst. of Arctic and Alpine Research, Boulder, CO (United States)

2001-06-01

Lake sediments are attractive repositories for paleoclimate proxy data because they are temporally continuous, undisturbed and datable. It is particularly true of lakes which are ubiquitous throughout the Arctic regions, enabling dense spatial coverage of sampling sites. In more recent times diatoms have been applied to a a variety of paleoenvironmental questions. However, these studies have been of limited usefulness because they lack a regional training set that would facilitate making quantitative paleoenvironmental inferences. This article provides this inferential tool, together with an example of its application. Conductivity, pH, summer lake water temperature, and mean annual air temperature have been identified as the significant controls over diatom assemblages from the surface sediments of 61 lakes on Baffin Island. Using weighted-averaging regression and calibration, predictive models for these parameters have been developed. Results show that the summer lake water temperature model provides realistic reconstructions when compared with other paleoenvironmental records. Over the past 5000 years the amplitude of reconstructed summer lake water temperature was found to be on the order of 4 degrees C, expressed primarily as progressive neoglacial cooling culminating in the Little Ice Age. Diatom-inferred summer water temperatures have increased by about 2 degrees C in the past 150 years, which is also in agreement with independent paleoclimatic reconstructions. The data obtained in this study complements similar efforts from the western Canadian Arctic and the northern reaches of Scandinavia, however, this is the first training set developed for lakes situated entirely north of the tree line. As such, it extends the applicability of diatoms for paleotemperature reconstructions well into the Arctic tundra biome. 45 refs., 1 tab., 10 figs., 1 appendix.

Declining summer snowfall in the Arctic: causes, impacts and feedbacks

Energy Technology Data Exchange (ETDEWEB)

Screen, James A.; Simmonds, Ian [University of Melbourne, School of Earth Sciences, Melbourne, VIC (Australia)

2012-06-15

Recent changes in the Arctic hydrological cycle are explored using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim. We document a pronounced decline in summer snowfall over the Arctic Ocean and Canadian Archipelago. The snowfall decline is diagnosed as being almost entirely caused by changes in precipitation form (snow turning to rain) with very little influence of decreases in total precipitation. The proportion of precipitation falling as snow has decreased as a result of lower-atmospheric warming. Statistically, over 99% of the summer snowfall decline is linked to Arctic warming over the past two decades. Based on the reanalysis snowfall data over the ice-covered Arctic Ocean, we derive an estimate for the amount of snow-covered ice. It is estimated that the area of snow-covered ice, and the proportion of sea ice covered by snow, have decreased significantly. We perform a series of sensitivity experiments in which inter-annual changes in snow-covered ice are either unaccounted for, or are parameterized. In the parameterized case, the loss of snow-on-ice results in a substantial decrease in the surface albedo over the Arctic Ocean, that is of comparable magnitude to the decrease in albedo due to the decline in sea ice cover. Accordingly, the solar input to the Arctic Ocean is increased, causing additional surface ice melt. We conclude that the decline in summer snowfall has likely contributed to the thinning of sea ice over recent decades. The results presented provide support for the existence of a positive feedback in association with warming-induced reductions in summer snowfall. (orig.)

Warm temperature acclimation impacts metabolism of paralytic shellfish toxins from Alexandrium minutum in commercial oysters.

Science.gov (United States)

Farrell, Hazel; Seebacher, Frank; O'Connor, Wayne; Zammit, Anthony; Harwood, D Tim; Murray, Shauna

2015-09-01

Species of Alexandrium produce potent neurotoxins termed paralytic shellfish toxins and are expanding their ranges worldwide, concurrent with increases in sea surface temperature. The metabolism of molluscs is temperature dependent, and increases in ocean temperature may influence both the abundance and distribution of Alexandrium and the dynamics of toxin uptake and depuration in shellfish. Here, we conducted a large-scale study of the effect of temperature on the uptake and depuration of paralytic shellfish toxins in three commercial oysters (Saccostrea glomerata and diploid and triploid Crassostrea gigas, n = 252 per species/ploidy level). Oysters were acclimated to two constant temperatures, reflecting current and predicted climate scenarios (22 and 27 °C), and fed a diet including the paralytic shellfish toxin-producing species Alexandrium minutum. While the oysters fed on A. minutum in similar quantities, concentrations of the toxin analogue GTX1,4 were significantly lower in warm-acclimated S. glomerata and diploid C. gigas after 12 days. Following exposure to A. minutum, toxicity of triploid C. gigas was not affected by temperature. Generally, detoxification rates were reduced in warm-acclimated oysters. The routine metabolism of the oysters was not affected by the toxins, but a significant effect was found at a cellular level in diploid C. gigas. The increasing incidences of Alexandrium blooms worldwide are a challenge for shellfish food safety regulation. Our findings indicate that rising ocean temperatures may reduce paralytic shellfish toxin accumulation in two of the three oyster types; however, they may persist for longer periods in oyster tissue. © 2015 John Wiley & Sons Ltd.

The importance of warm season warming to western U.S. streamflow changes

Science.gov (United States)

Das, T.; Pierce, D.W.; Cayan, D.R.; Vano, J.A.; Lettenmaier, D.P.

2011-01-01

Warm season climate warming will be a key driver of annual streamflow changes in four major river basins of the western U.S., as shown by hydrological model simulations using fixed precipitation and idealized seasonal temperature changes based on climate projections with SRES A2 forcing. Warm season (April-September) warming reduces streamflow throughout the year; streamflow declines both immediately and in the subsequent cool season. Cool season (October-March) warming, by contrast, increases streamflow immediately, partially compensating for streamflow reductions during the subsequent warm season. A uniform warm season warming of 3C drives a wide range of annual flow declines across the basins: 13.3%, 7.2%, 1.8%, and 3.6% in the Colorado, Columbia, Northern and Southern Sierra basins, respectively. The same warming applied during the cool season gives annual declines of only 3.5%, 1.7%, 2.1%, and 3.1%, respectively. Copyright 2011 by the American Geophysical Union.

Lightning Evolution In Two North Central Florida Summer Multicell Storms and Three Winter/Spring Frontal Storms

Science.gov (United States)

Caicedo, J. A.; Uman, M. A.; Pilkey, J. T.

2018-01-01

We present the first lightning evolution studies, via the Lightning Mapping Array (LMA) and radar, performed in North Central Florida. Parts of three winter/spring frontal storms (cold season) and two complete summer (warm season) multicell storms are studied. Storm parameters measured are as follows: total number of flashes, flash-type classification, first flashes, flash initiation altitude, flash initiation power, flash rate (flashes per minute), charge structure, altitude and temperature ranges of the inferred charge regions, atmospheric isotherm altitude, radar base reflectivity (dBZ), and radar echo tops (EET). Several differences were found between summer multicell and winter/spring frontal storms in North Central Florida: (1) in winter/spring storms, the range of altitudes that all charge regions occupy is up to 1 km lower in altitude than in summer storms, as are the 0°C, -10°C, and -20°C isotherms; (2) lightning activity in summer storms is highly correlated with changes in radar signatures, in particular, echo tops; and (3) the LMA average initiation power of all flash types in winter/frontal storms is about an order of magnitude larger than that for summer storms. In relation to storms in other geographical locations, North Central Florida seasonal storms were found to have similarities in most parameters studied with a few differences, examples in Florida being (1) colder initiation altitudes for intracloud flashes, (2) charge regions occupying larger ranges of atmospheric temperatures, and (3) winter/spring frontal storms not having much lightning activity in the stratiform region.

Global lake response to the recent warming hiatus

Science.gov (United States)

Winslow, Luke A.; Leach, Taylor H.; Rose, Kevin C.

2018-05-01

Understanding temporal variability in lake warming rates over decadal scales is important for understanding observed change in aquatic systems. We analyzed a global dataset of lake surface water temperature observations (1985‑2009) to examine how lake temperatures responded to a recent global air temperature warming hiatus (1998‑2012). Prior to the hiatus (1985‑1998), surface water temperatures significantly increased at an average rate of 0.532 °C decade‑1 (±0.214). In contrast, water temperatures did not change significantly during the hiatus (average rate ‑0.087 °C decade‑1 ±0.223). Overall, 83% of lakes in our dataset (129 of 155) had faster warming rates during the pre-hiatus period than during the hiatus period. These results demonstrate that lakes have exhibited decadal-scale variability in warming rates coherent with global air temperatures and represent an independent line of evidence for the recent warming hiatus. Our analyses provide evidence that lakes are sentinels of broader climatological processes and indicate that warming rates based on datasets where a large proportion of observations were collected during the hiatus period may underestimate longer-term trends.

Temperature responses of some North Atlantic Cladophora species (Chlorophyceae) in relation to their geographic distribution

Science.gov (United States)

Cambridge, M.; Breeman, A. M.; van Oosterwijk, R.; van den Hoek, C.

1984-09-01

The temperature responses for growth and survival have been experimentally tested for 6 species of the green algal genus Cladophora (Chlorophyceae; Cladophorales) (all isolated from Roscoff, Brittany, France, one also from Connecticut, USA), selected from 4 distribution groups, in order to determine which phase in the annual temperature regime might prevent the spread of a species beyond its present latitudinal range on the N. Atlantic coasts. For five species geographic limits could be specifically defined as due to a growth limit in the growing season or to a lethal limit in the adverse season. These species were: (1) C. coelothrix (Amphiatlantic tropical to warm temperate), with a northern boundary on the European coasts formed by a summer growth limit near the 12°C August isotherm. On the American coasts sea temperatures should allow its occurrence further north. (2) C. vagabunda (Amphiatlantic tropical to temperate), with a northern boundary formed by a summer growth limit near the 15°C August isotherm on both sides of the Atlantic. (3) C. dalmatica, as for C. vagabunda. (4) C. hutchinsiae (Mediterranean-Atlantic warm temperate), with a northern boundary formed by a summer growth limit near the 12°C August isotherm, and possibly also a winter lethal limit near the 6°C February isotherm; and a southern boundary formed by a southern lethal limit near the 26°C August isotherm. It is absent from the warm temperate American coast because its lethal limits, 5° and 30°C, are regularly reached there. (5) Preliminary data for C. rupestris (Amphiatlantic temperate), suggest the southeastern boundary on the African coast to be a summer lethal limit near the 26°C August isotherm; the southwestern boundary on the American coast lies on the 20°C August isotherm. For one species, C. albida, the experimental growth and survival range was wider than expected from its geographic distribution, and reasons to account for this are suggested.

Experimental winter warming modifies thermal performance and primes acorn ants for warm weather

DEFF Research Database (Denmark)

MacLean, Heidi J.; Penick, Clint A.; Dunn, Robert R.

2017-01-01

The frequency of warm winter days is increasing under global climate change, but how organisms respond to warmer winters is not well understood. Most studies focus on growing season responses to warming. Locomotor performance is often highly sensitive to temperature, and can determine fitness...... outcomes through a variety of mechanisms including resource acquisition and predator escape. As a consequence, locomotor performance, and its impacts on fitness, may be strongly affected by winter warming in winter-active species. Here we use the acorn ant, Temnothorax curvispinosus, to explore how thermal...... performance (temperature-driven plasticity) in running speed is influenced by experimental winter warming of 3–5 °C above ambient in a field setting. We used running speed as a measure of performance as it is a common locomotor trait that influences acquisition of nest sites and food in acorn ants...

Regional tree growth and inferred summer climate in the Winnipeg River basin, Canada, since AD 1783

Science.gov (United States)

St. George, Scott; Meko, David M.; Evans, Michael N.

2008-09-01

A network of 54 ring-width chronologies is used to estimate changes in summer climate within the Winnipeg River basin, Canada, since AD 1783. The basin drains parts of northwestern Ontario, northern Minnesota and southeastern Manitoba, and is a key area for hydroelectric power production. Most chronologies were developed from Pinus resinosa and P. strobus, with a limited number of Thuja occidentalis, Picea glauca and Pinus banksiana. The dominant pattern of regional tree growth can be recovered using only the nine longest chronologies, and is not affected by the method used to remove variability related to age or stand dynamics from individual trees. Tree growth is significantly, but weakly, correlated with both temperature (negatively) and precipitation (positively) during summer. Simulated ring-width chronologies produced by a process model of tree-ring growth exhibit similar relationships with summer climate. High and low growth across the region is associated with cool/wet and warm/dry summers, respectively; this relationship is supported by comparisons with archival records from early 19th century fur-trading posts. The tree-ring record indicates that summer droughts were more persistent in the 19th and late 18th century, but there is no evidence that drought was more extreme prior to the onset of direct monitoring.

A sensitivity study to global desertification in cold and warm climates: results from the IPSL OAGCM model

Energy Technology Data Exchange (ETDEWEB)

Alkama, Ramdane [GAME/CNRM, CNRS/Meteo-France, Toulouse (France); Kageyama, Masa; Ramstein, Gilles [LSCE/IPSL UMR CEA-CNRS-UVSQ 8212, Gif sur Yvette (France)

2012-04-15

Many simulations have been devoted to study the impact of global desertification on climate, but very few have quantified this impact in very different climate contexts. Here, the climatic impacts of large-scale global desertification in warm (2100 under the SRES A2 scenario forcing), modern and cold (Last Glacial Maximum, 21 thousand years ago) climates are assessed by using the IPSL OAGCM. For each climate, two simulations have been performed, one in which the continents are covered by modern vegetation, the other in which global vegetation is changed to desert i.e. bare soil. The comparison between desert and present vegetation worlds reveals that the prevailing signal in terms of surface energy budget is dominated by the reduction of upward latent heat transfer. Replacing the vegetation by bare soil has similar impacts on surface air temperature South of 20 N in all three climatic contexts, with a warming over tropical forests and a slight cooling over semi-arid and arid areas, and these temperature changes are of the same order of magnitude. North of 20 N, the difference between the temperatures simulated with present day vegetation and in a desert world is mainly due to the change in net radiation related to the modulation of the snow albedo by vegetation, which is obviously absent in the desert world simulations. The enhanced albedo in the desert world simulations induces a large temperature decrease, especially during summer in the cold and modern climatic contexts, whereas the largest difference occurs during winter in the warm climate. This temperature difference requires a larger heat transport to the northern high latitudes. Part of this heat transport increase is achieved through an intensification of the Atlantic Meridional Overturning Circulation. This intensification reduces the sea-ice extent and causes a warming over the North Atlantic and Arctic oceans in the warm climate context. In contrast, the large cooling North of 20 N in both the modern

Climate signals in a multispecies tree-ring network from central and southern Italy and reconstruction of the late summer temperatures since the early 1700s

Science.gov (United States)

Leonelli, Giovanni; Coppola, Anna; Salvatore, Maria Cristina; Baroni, Carlo; Battipaglia, Giovanna; Gentilesca, Tiziana; Ripullone, Francesco; Borghetti, Marco; Conte, Emanuele; Tognetti, Roberto; Marchetti, Marco; Lombardi, Fabio; Brunetti, Michele; Maugeri, Maurizio; Pelfini, Manuela; Cherubini, Paolo; Provenzale, Antonello; Maggi, Valter

2017-11-01

A first assessment of the main climatic drivers that modulate the tree-ring width (RW) and maximum latewood density (MXD) along the Italian Peninsula and northeastern Sicily was performed using 27 forest sites, which include conifers (RW and MXD) and broadleaves (only RW). Tree-ring data were compared using the correlation analysis of the monthly and seasonal variables of temperature, precipitation and standardized precipitation index (SPI, used to characterize meteorological droughts) against each species-specific site chronology and against the highly sensitive to climate (HSTC) chronologies (based on selected indexed individual series). We find that climate signals in conifer MXD are stronger and more stable over time than those in conifer and broadleaf RW. In particular, conifer MXD variability is directly influenced by the late summer (August, September) temperature and is inversely influenced by the summer precipitation and droughts (SPI at a timescale of 3 months). The MXD sensitivity to August-September (AS) temperature and to summer drought is mainly driven by the latitudinal gradient of summer precipitation amounts, with sites in the northern Apennines showing stronger climate signals than sites in the south. Conifer RW is influenced by the temperature and drought of the previous summer, whereas broadleaf RW is more influenced by summer precipitation and drought of the current growing season. The reconstruction of the late summer temperatures for the Italian Peninsula for the past 300 years, based on the HSTC chronology of conifer MXD, shows a stable model performance that underlines periods of climatic cooling (and likely also wetter conditions) in 1699, 1740, 1814, 1914 and 1938, and follows well the variability of the instrumental record and of other tree-ring-based reconstructions in the region. Considering a 20-year low-pass-filtered series, the reconstructed temperature record consistently deviates divergence may also be due to the precipitation

Climate signals in a multispecies tree-ring network from central and southern Italy and reconstruction of the late summer temperatures since the early 1700s

Directory of Open Access Journals (Sweden)

G. Leonelli

2017-11-01

Full Text Available A first assessment of the main climatic drivers that modulate the tree-ring width (RW and maximum latewood density (MXD along the Italian Peninsula and northeastern Sicily was performed using 27 forest sites, which include conifers (RW and MXD and broadleaves (only RW. Tree-ring data were compared using the correlation analysis of the monthly and seasonal variables of temperature, precipitation and standardized precipitation index (SPI, used to characterize meteorological droughts against each species-specific site chronology and against the highly sensitive to climate (HSTC chronologies (based on selected indexed individual series. We find that climate signals in conifer MXD are stronger and more stable over time than those in conifer and broadleaf RW. In particular, conifer MXD variability is directly influenced by the late summer (August, September temperature and is inversely influenced by the summer precipitation and droughts (SPI at a timescale of 3 months. The MXD sensitivity to August–September (AS temperature and to summer drought is mainly driven by the latitudinal gradient of summer precipitation amounts, with sites in the northern Apennines showing stronger climate signals than sites in the south. Conifer RW is influenced by the temperature and drought of the previous summer, whereas broadleaf RW is more influenced by summer precipitation and drought of the current growing season. The reconstruction of the late summer temperatures for the Italian Peninsula for the past 300 years, based on the HSTC chronology of conifer MXD, shows a stable model performance that underlines periods of climatic cooling (and likely also wetter conditions in 1699, 1740, 1814, 1914 and 1938, and follows well the variability of the instrumental record and of other tree-ring-based reconstructions in the region. Considering a 20-year low-pass-filtered series, the reconstructed temperature record consistently deviates < 1 °C from the instrumental

Warmed Winter Water Temperatures Alter Reproduction in Two Fish Species

Science.gov (United States)

Firkus, Tyler; Rahel, Frank J.; Bergman, Harold L.; Cherrington, Brian D.

2018-02-01

We examined the spawning success of Fathead Minnows ( Pimephales promelas) and Johnny Darters ( Etheostoma nigrum) exposed to elevated winter water temperatures typical of streams characterized by anthropogenic thermal inputs. When Fathead Minnows were exposed to temperature treatments of 12, 16, or 20 °C during the winter, spawning occurred at 16 and 20 °C but not 12 °C. Eggs were deposited over 9 weeks before winter spawning ceased. Fathead Minnows from the three winter temperature treatments were then exposed to a simulated spring transition. Spawning occurred at all three temperature treatments during the spring, but fish from the 16° and 20 °C treatment had delayed egg production indicating a latent effect of warm winter temperatures on spring spawning. mRNA analysis of the egg yolk protein vitellogenin showed elevated expression in female Fathead Minnows at 16 and 20 °C during winter spawning that decreased after winter spawning ceased, whereas Fathead Minnows at 12 °C maintained comparatively low expression during winter. Johnny Darters were exposed to 4 °C to represent winter temperatures in the absence of thermal inputs, and 12, 16, and 20 °C to represent varying degrees of winter thermal pollution. Johnny Darters spawned during winter at 12, 16, and 20 °C but not at 4 °C. Johnny Darters at 4 °C subsequently spawned following a simulated spring period while those at 12, 16, and 20 °C did not. Our results indicate elevated winter water temperatures common in effluent-dominated streams can promote out-of-season spawning and that vitellogenin expression is a useful indicator of spawning readiness for fish exposed to elevated winter temperatures.

Future weather types and their influence on mean and extreme climate indices for precipitation and temperature in Central Europe

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Ulf Riediger

2014-09-01

Full Text Available In Central Europe, the spatial and temporal distributions of precipitation and temperature are determined by the occurrence of major weather types. In this paper, we examine climate indices (i.e. mean values or hot, cold, wet and dry days for different weather types in a recent (1971–2000 and future climate (2070–2099. The weather types are classified objectively for the control run and for the A1B scenario with an ensemble of eight global climate simulations (GCM to be compared with different reanalyses. To derive climate indices, the high-resolution, regionalized reference dataset HYRAS and an ensemble of nine regional climate simulations (RCM are used. Firstly, the reliability of simulated weather patterns and their climate indices are tested in the control period. The reanalyses circulation climatology can be reproduced well by the GCM ensemble mean. For temperature and precipitation, each climate index is characterized and evaluated in terms of defined weather patterns. The comparison of HYRAS and RCM data show reliable mean temperature values with differences between weather classes by +2$+2$ to -6$-6$ °C during winter (13 to 19 °C in summer. The analysis of observed and simulated precipitation reveal that mean winter precipitation is significantly influenced by the direction of air flow, while in summer, mesoscale atmospheric patterns of cyclonic rotation play a larger role. Secondly, the analysis of potential future changes simulated by the RCM ensemble were able to demonstrate that weather type changes, superior climate trends (such as mean warming and their interaction lead to major changes for precipitation and temperature in Central Europe. While temperature differences between cold and warm weather types are nearly stable over time, the ensemble temperature changes (with a range of +2$+2$ to +4$+4$ °C reinforce warm/hot conditions in the future winter and summer. Milder, wetter winters can be explained by an increased

The Impact of Warm Pool El Nino Events on Antarctic Ozone

Science.gov (United States)

Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.

2011-01-01

Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a warming of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN events as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN events with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN events and the second set representing neutral ENSO events, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN events on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.

Dendroclimatic transfer functions revisited: Little Ice Age and Medieval Warm Period summer temperatures reconstructed using artificial neural networks and linear algorithms

Energy Technology Data Exchange (ETDEWEB)

Helama, S.; Holopainen, J.; Eronen, M. [Department of Geology, University of Helsinki, (Finland); Makarenko, N.G. [Russian Academy of Sciences, St. Petersburg (Russian Federation). Pulkovo Astronomical Observatory; Karimova, L.M.; Kruglun, O.A. [Institute of Mathematics, Almaty (Kazakhstan); Timonen, M. [Finnish Forest Research Institute, Rovaniemi Research Unit (Finland); Merilaeinen, J. [SAIMA Unit of the Savonlinna Department of Teacher Education, University of Joensuu (Finland)

2009-07-01

Tree-rings tell of past climates. To do so, tree-ring chronologies comprising numerous climate-sensitive living-tree and subfossil time-series need to be 'transferred' into palaeoclimate estimates using transfer functions. The purpose of this study is to compare different types of transfer functions, especially linear and nonlinear algorithms. Accordingly, multiple linear regression (MLR), linear scaling (LSC) and artificial neural networks (ANN, nonlinear algorithm) were compared. Transfer functions were built using a regional tree-ring chronology and instrumental temperature observations from Lapland (northern Finland and Sweden). In addition, conventional MLR was compared with a hybrid model whereby climate was reconstructed separately for short- and long-period timescales prior to combining the bands of timescales into a single hybrid model. The fidelity of the different reconstructions was validated against instrumental climate data. The reconstructions by MLR and ANN showed reliable reconstruction capabilities over the instrumental period (AD 1802-1998). LCS failed to reach reasonable verification statistics and did not qualify as a reliable reconstruction: this was due mainly to exaggeration of the low-frequency climatic variance. Over this instrumental period, the reconstructed low-frequency amplitudes of climate variability were rather similar by MLR and ANN. Notably greater differences between the models were found over the actual reconstruction period (AD 802-1801). A marked temperature decline, as reconstructed by MLR, from the Medieval Warm Period (AD 931-1180) to the Little Ice Age (AD 1601-1850), was evident in all the models. This decline was approx. 0.5 C as reconstructed by MLR. Different ANN based palaeotemperatures showed simultaneous cooling of 0.2 to 0.5 C, depending on algorithm. The hybrid MLR did not seem to provide further benefit above conventional MLR in our sample. The robustness of the conventional MLR over the calibration

Climatic warming destabilizes forest ant communities.

Science.gov (United States)

Diamond, Sarah E; Nichols, Lauren M; Pelini, Shannon L; Penick, Clint A; Barber, Grace W; Cahan, Sara Helms; Dunn, Robert R; Ellison, Aaron M; Sanders, Nathan J; Gotelli, Nicholas J

2016-10-01

How will ecological communities change in response to climate warming? Direct effects of temperature and indirect cascading effects of species interactions are already altering the structure of local communities, but the dynamics of community change are still poorly understood. We explore the cumulative effects of warming on the dynamics and turnover of forest ant communities that were warmed as part of a 5-year climate manipulation experiment at two sites in eastern North America. At the community level, warming consistently increased occupancy of nests and decreased extinction and nest abandonment. This consistency was largely driven by strong responses of a subset of thermophilic species at each site. As colonies of thermophilic species persisted in nests for longer periods of time under warmer temperatures, turnover was diminished, and species interactions were likely altered. We found that dynamical (Lyapunov) community stability decreased with warming both within and between sites. These results refute null expectations of simple temperature-driven increases in the activity and movement of thermophilic ectotherms. The reduction in stability under warming contrasts with the findings of previous studies that suggest resilience of species interactions to experimental and natural warming. In the face of warmer, no-analog climates, communities of the future may become increasingly fragile and unstable.

Biomass production in experimental grasslands of different species richness during three years of climate warming

Science.gov (United States)

de Boeck, H. J.; Lemmens, C. M. H. M.; Zavalloni, C.; Gielen, B.; Malchair, S.; Carnol, M.; Merckx, R.; van den Berge, J.; Ceulemans, R.; Nijs, I.

2008-04-01

Here we report on the single and combined impacts of climate warming and species richness on the biomass production in experimental grassland communities. Projections of a future warmer climate have stimulated studies on the response of terrestrial ecosystems to this global change. Experiments have likewise addressed the importance of species numbers for ecosystem functioning. There is, however, little knowledge on the interplay between warming and species richness. During three years, we grew experimental plant communities containing one, three or nine grassland species in 12 sunlit, climate-controlled chambers in Wilrijk, Belgium. Half of these chambers were exposed to ambient air temperatures (unheated), while the other half were warmed by 3°C (heated). Equal amounts of water were added to heated and unheated communities, so that warming would imply drier soils if evapotranspiration was higher. Biomass production was decreased due to warming, both aboveground (-29%) and belowground (-25%), as negative impacts of increased heat and drought stress in summer prevailed. Complementarity effects, likely mostly through both increased aboveground spatial complementarity and facilitative effects of legumes, led to higher shoot and root biomass in multi-species communities, regardless of the induced warming. Surprisingly, warming suppressed productivity the most in 9-species communities, which may be attributed to negative impacts of intense interspecific competition for resources under conditions of high abiotic stress. Our results suggest that warming and the associated soil drying could reduce primary production in many temperate grasslands, and that this will not necessarily be mitigated by efforts to maintain or increase species richness.