Maximum Summer Temperatures Research Articles

Spatial and temporal variation in daily temperature indices in summer and winter seasons over India (1969–2012)

Spatial and temporal variations in summer and winter extreme temperature indices are studied by using daily maximum and minimum temperatures data from 227 surface meteorological stations well distributed over India for the period 1969–2012. For this purpose, time series for six extreme temperature indices namely, hot days (HD), very hot days (VHD), extremely hot days (EHD), cold nights (CN), very cold nights (VCN), and extremely cold nights (ECN) are calculated for all the stations. In addition, time series for mean extreme temperature indices of summer and winter seasons are also analyzed. Study reveals high variability in spatial distribution of threshold temperatures of extreme temperature indices over the country. In general, increasing trends are observed in summer hot days indices and decreasing trends in winter cold night indices over most parts of the country. The results obtained in this study indicate warming in summer maximum and winter minimum temperatures over India. Averaged over India, trends in summer hot days indices HD, VHD, and EHD are significantly increasing (+1.0, +0.64, and +0.32 days/decade, respectively) and winter cold night indices CN, VCN, and ECN are significantly decreasing (−0.93, −0.47, and −0.15 days/decade, respectively). Also, it is observed that the impact of extreme temperature is higher along the west coast for summer and east coast for winter.

Temperature Modulates the Effects of Ocean Acidification on Intestinal Ion Transport in Atlantic Cod, Gadus morhua

CO2-driven seawater acidification has been demonstrated to enhance intestinal bicarbonate secretion rates in teleosts, leading to an increased release of CaCO3 under simulated ocean acidification scenarios. In this study, we investigated if increasing CO2 levels stimulate the intestinal acid–base regulatory machinery of Atlantic cod (Gadus morhua) and whether temperatures at the upper limit of thermal tolerance stimulate or counteract ion regulatory capacities. Juvenile G. morhua were acclimated for 4 weeks to three CO2 levels (550, 1200, and 2200 μatm) covering present and near-future natural variability, at optimum (10°C) and summer maximum temperature (18°C), respectively. Immunohistochemical analyses revealed the subcellular localization of ion transporters, including Na+/K+-ATPase (NKA), Na+/H+-exchanger 3 (NHE3), Na+/ cotransporter (NBC1), pendrin-like Cl−/ exchanger (SLC26a6), V-type H+-ATPase subunit a (VHA), and Cl− channel 3 (CLC3) in epithelial cells of the anterior intestine. At 10°C, proteins and mRNA were generally up-regulated for most transporters in the intestinal epithelium after acclimation to higher CO2 levels. This supports recent findings demonstrating increased intestinal secretion rates in response to CO2 induced seawater acidification. At 18°C, mRNA expression and protein concentrations of most ion transporters remained unchanged or were even decreased, suggesting thermal compensation. This response may be energetically favorable to retain blood levels to stabilize pHe, but may negatively affect intestinal salt and water resorption of marine teleosts in future oceans.

High Summer Temperatures and Mortality in Estonia.

BackgroundOn-going climate change is predicted to result in a growing number of extreme weather events—such as heat waves—throughout Europe. The effect of high temperatures and heat waves are already having an important impact on public health in terms of increased mortality, but studies from an Estonian setting are almost entirely missing. We investigated mortality in relation to high summer temperatures and the time course of mortality in a coastal and inland region of Estonia.MethodsWe collected daily mortality data and daily maximum temperature for a coastal and an inland region of Estonia. We applied a distributed lag non-linear model to investigate heat related mortality and the time course of mortality in Estonia.ResultsWe found an immediate increase in mortality associated with temperatures exceeding the 75th percentile of summer maximum temperatures, corresponding to approximately 23°C. This increase lasted for a couple of days in both regions. The total effect of elevated temperatures was not lessened by significant mortality displacement.DiscussionWe observed significantly increased mortality in Estonia, both on a country level as well as for a coastal region and an inland region with a more continental climate. Heat related mortality was higher in the inland region as compared to the coastal region, however, no statistically significant differences were observed. The lower risks in coastal areas could be due to lower maximum temperatures and cooling effects of the sea, but also better socioeconomic condition. Our results suggest that region specific estimates of the impacts of temperature extremes on mortality are needed.

Recent warming evidence inferred from a tree-ring-based winter-half year minimum temperature reconstruction in northwestern Yichang, South Central China, and its relation to the large-scale circulation anomalies.

High-resolution winter temperature reconstructions in China are rare, yet vital for the comprehensive understanding of past climate change. In the present work, the first winter-half year minimum mean temperature from previous November to current April in northwestern Yichang, South Central China, was reconstructed back to 1875 based on tree-ring material. The reconstruction can explain 55% of the variance over the calibration period during 1955-2011. The temperature maintained at comparatively low level before 1958, and an abnormal warming was seen since 1959. However, the warming trend stagnated after 2000AD. 2001-2010 was the warmest decade not only during the instrumental period but also during the whole reconstructed period. The reconstruction indicates good spatial resemblance to other temperatures series in adjacent areas and Northern Hemisphere, yet the recent warming in this study is earlier and more prominent than that of Southeast China. This work also manifests that the winter-half year minimum temperature in study area has good agreement with summer (June-September) maximum temperature variation in Southeast China at decadal scale, except that the winter-half year warming in recent decades is more evident than summer. This reconstruction is not only useful in improving our knowledge of long-term temperature variation but also useful in predicting the tree growth dynamics in the future in the study area.

Vegetation productivity responds to sub‐annual climate conditions across semiarid biomes

AbstractIn the southwest United States, the current prolonged warm drought is similar to the predicted future climate change scenarios for the region. This study aimed to determine patterns in vegetation response to the early 21st century drought across multiple biomes. We hypothesized that different biomes (forests, shrublands, and grasslands) would have different relative sensitivities to both climate drivers (precipitation and temperature) and legacy effects (previous‐year's productivity). We tested this hypothesis at eight Ameriflux sites in various Southwest biomes using NASA Moderate‐resolution Imaging Spectroradiometer Enhanced Vegetation Index (EVI) from 2001 to 2013. All sites experienced prolonged dry conditions during the study period. The impact of combined precipitation and temperature on Southwest ecosystems at both annual and sub‐annual timescales was tested using Standardized Precipitation Evapotranspiration Index (SPEI). All biomes studied had critical sub‐annual climate periods during which precipitation and temperature influenced production. In forests, annual peak greenness (EVImax) was best predicted by 9‐month SPEI calculated in July (i.e., January–July). In shrublands and grasslands, EVImax was best predicted by SPEI in July through September, with little effect of the previous year's EVImax. Daily gross ecosystem production (GEP) derived from flux tower data yielded further insights into the complex interplay between precipitation and temperature. In forests, GEP was driven by cool‐season precipitation and constrained by warm‐season maximum temperature. GEP in both shrublands and grasslands was driven by summer precipitation and constrained by high daily summer maximum temperatures. In grasslands, there was a negative relationship between temperature and GEP in July, but no relationship in August and September. Consideration of sub‐annual climate conditions and the inclusion of the effect of temperature on the water balance allowed us to generalize the functional responses of vegetation to predicted future climate conditions. We conclude that across biomes, drought conditions during critical sub‐annual climate periods could have a strong negative impact on vegetation production in the southwestern United States.

Lethal and sub-lethal responses of the biogenic reef forming polychaete Sabellaria alveolata to aqueous chlorine and temperature

Sabellaria alveolata, a reef-forming marine polychaete, was exposed to aqueous chlorine which is routinely used as an anti-fouling agent in power station cooling water. Worms were treated to a range of chlorination levels (0, 0.02, 0.1 and 0.5 mg l−1 Total Residual Oxidant referred to as control, low, intermediate and high TRO) at mean and maximum summer temperatures (18 and 23 °C respectively). Overall mortality was relatively low, however a combination of high temperature and intermediate and high TRO resulted in a significant increase in mortality compared to the control and low TRO treatments. In contrast the extension of dwelling tubes was reduced at high TRO, but increased at low and intermediate TRO levels relative to the controls independent of temperature. Finally, tube strength was found to decrease with increasing TRO, again independent of temperature. On the basis of these findings, S. alveolata can be considered tolerant of one month exposures to low TRO at water temperatures up to and including the summer maxima for southern UK waters. However, at higher TRO levels and during warm weather, high mortality would be predicted.

Ancestral genetic diversity associated with the rapid spread of stress-tolerant coral symbionts in response to Holocene climate change

Coral communities in the Persian/Arabian Gulf (PAG) withstand unusually high salinity levels and regular summer temperature maxima of up to ∼35 °C that kill conspecifics elsewhere. Due to the recent formation of the PAG and its subsequent shift to a hot climate, these corals have had only <6,000 y to adapt to these extreme conditions and can therefore inform on how coral reefs may respond to global warming. One key to coral survival in the world's warmest reefs are symbioses with a newly discovered alga,Symbiodinium thermophilum Currently, it is unknown whether this symbiont originated elsewhere or emerged from unexpectedly fast evolution catalyzed by the extreme environment. Analyzing genetic diversity of symbiotic algae across >5,000 km of the PAG, the Gulf of Oman, and the Red Sea coastline, we show thatS. thermophilumis a member of a highly diverse, ancient group of symbionts cryptically distributed outside the PAG. We argue that the adjustment to temperature extremes by PAG corals was facilitated by the positive selection of preadapted symbionts. Our findings suggest that maintaining the largest possible pool of potentially stress-tolerant genotypes by protecting existing biodiversity is crucial to promote rapid adaptation to present-day climate change, not only for coral reefs, but for ecosystems in general.

Testing for functional convergence of temperate rainforest tree assemblages in Chile and New Zealand

ABSTRACTAn important tenet of biogeography and comparative ecology is that disjunct assemblages in similar physical environments are functionally more similar to each other than to assemblages from other environments. Temperate rainforests in South America, New Zealand and Australia share certain physiognomic similarities, but we are not aware of any statistical evidence that these disjunct plant assemblages share a distinctive suite of functional traits, or trait combinations. We compiled height, leaf, wood and reproductive traits from the 25 commonest arborescent species at Chilean and New Zealand sites matched for summer rainfall, summer maximum temperatures, and winter minimum temperatures. We then used multivariate tests of trait convergence. Tropical and subtropical assemblages served as out-groups. PERMANOVA showed convergence of trait centroids at the two temperate sites, where trees on average had denser wood and smaller leaves than trees at the (sub)tropical sites. Principal components analyses carried out separately on each assemblage showed that the Chilean and New Zealand assemblages were also the most similar pair in terms of trait relationships, although New Zealand also shared strong similarities with subtropical Argentina. The main axis of variation in both temperate assemblages ranged from small, short-lived understorey trees with soft leaves, to emergents with sclerophyllous leaves and fairly dense wood. However, the New Zealand assemblage was much richer in small trees with soft leaves than its Chilean counterpart; possible historical influences on this difference include conditions favouring radiation of small trees during the late Neogene in New Zealand, competition from Chusquea bamboos in Chile and the historical absence of browsing mammals from New Zealand. Environmental filtering has produced similar values of individual traits in Chile and New Zealand, but only partial convergence of functional trait combinations. As far as we know, this is the first study to statistically test whether disjunct tree assemblages on climatically matched sites are more functionally similar to each other than to assemblages from other environments.

EXTREME MAXIMUM AND MINIMUM AIR TEMPERATURE IN MEDİTERRANEAN COASTS IN TURKEY

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 minimum temperatures 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.

Habitat Suitability Model for the Distribution of Ixodes scapularis (Acari: Ixodidae) in Minnesota.

Ixodes scapularis Say, the black-legged tick, is the primary vector in the eastern United States of several pathogens causing human diseases including Lyme disease, anaplasmosis, and babesiosis. Over the past two decades, I. scapularis-borne diseases have increased in incidence as well as geographic distribution. Lyme disease exists in two major foci in the United States, one encompassing northeastern states and the other in the Upper Midwest. Minnesota represents a state with an appreciable increase in counties reporting I. scapularis-borne illnesses, suggesting geographic expansion of vector populations in recent years. Recent tick distribution records support this assumption. Here, we used those records to create a fine resolution, subcounty-level distribution model for I. scapularis using variable response curves in addition to tests of variable importance. The model identified 19% of Minnesota as potentially suitable for establishment of the tick and indicated with high accuracy (AUC = 0.863) that the distribution is driven by land cover type, summer precipitation, maximum summer temperatures, and annual temperature variation. We provide updated records of established populations near the northwestern species range limit and present a model that increases our understanding of the potential distribution of I. scapularis in Minnesota.

A dynamic organic Rankine cycle using a zeotropic mixture as the working fluid with composition tuning to match changing ambient conditions

Air-cooled condensers are widely used for Organic Rankine Cycle (ORC) power plants where cooling water is unavailable or too costly, but they are then vulnerable to changing ambient air temperatures especially in continental climates, where the air temperature difference between winter and summer can be over 40°C. A conventional ORC system using a single component working fluid has to be designed according to the maximum air temperature in summer and thus operates far from optimal design conditions for most of the year, leading to low annual average efficiencies. This research proposes a novel dynamic ORC that uses a binary zeotropic mixture as the working fluid, with mechanisms in place to adjust the mixture composition dynamically during operation in response to changing heat sink conditions, significantly improving the overall efficiency of the plant. The working principle of the dynamic ORC concept is analysed. The case study results show that the annual average thermal efficiency can be improved by up to 23% over a conventional ORC when the heat source is 100°C, while the evaluated increase of the capital cost is less than 7%. The dynamic ORC power plants are particularly attractive for low temperature applications, delivering shorter payback periods compared to conventional ORC systems.

Tests of ecogeographical relationships in a non-native species: what rules avian morphology?

The capacity of non-native species to undergo rapid adaptive change provides opportunities to research contemporary evolution through natural experiments. This capacity is particularly true when considering ecogeographical rules, to which non-native species have been shown to conform within relatively short periods of time. Ecogeographical rules explain predictable spatial patterns of morphology, physiology, life history and behaviour. We tested whether Australian populations of non-native starling, Sturnus vulgaris, introduced to the country approximately 150years ago, exhibited predicted environmental clines in body size, appendage size and heart size (Bergmann's, Allen's and Hesse's rules, respectively). Adult starlings (n=411) were collected from 28 localities from across eastern Australia from 2011 to 2012. Linear models were constructed to examine the relationships between morphology and local environment. Patterns of variation in body mass and bill surface area were consistent with Bergmann's and Allen's rules, respectively (small body size and larger bill size in warmer climates), with maximum summer temperature being a strongly weighted predictor of both variables. In the only intraspecific test of Hesse's rule in birds to date, we found no evidence to support the idea that relative heart size will be larger in individuals which live in colder climates. Our study does provide evidence that maximum temperature is a strong driver of morphological adaptation for starlings in Australia. The changes in morphology presented here demonstrate the potential for avian species to make rapid adaptive changes in relation to a changing climate to ameliorate the effects of heat stress.

The Relationships between Climate Variability and Crop Yield in a Mountainous Environment: A Case Study in Lamjung District, Nepal

Several studies have concluded that mountainous countries such as Nepal are more vulnerable to climate change; thus, a changing climate should have a significant impact on crop yields. This work aims to explore the impact of climate change on major crop yields in the mountainous parts of Nepal and to determine their relationships based on a regression model between historical climatic data and yield data for food crops. The study starts with an analysis of the last 30 years of climatic data from Lamjung district. Mann-Kendall and Sen’s Slope methods have been used for the trend analysis and quantification. The results showed an increase in temperature of approximately 0.02 °C to 0.07 °C per year in different seasons and a mixed trend in precipitation. Although there was no significant impact of the climate variables on the yields of all crops, the regression analysis revealed negative relationships between maize yield and summer precipitation and between wheat yield and winter minimum temperature, and a positive relationship between millet yield and summer maximum temperature.

Climate variables explain neutral and adaptive variation within salmonid metapopulations: the importance of replication in landscape genetics.

Understanding how environmental variation influences population genetic structure is important for conservation management because it can reveal how human stressors influence population connectivity, genetic diversity and persistence. We used riverscape genetics modelling to assess whether climatic and habitat variables were related to neutral and adaptive patterns of genetic differentiation (population-specific and pairwise FST ) within five metapopulations (79 populations, 4583 individuals) of steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin, USA. Using 151 putatively neutral and 29 candidate adaptive SNP loci, we found that climate-related variables (winter precipitation, summer maximum temperature, winter highest 5% flow events and summer mean flow) best explained neutral and adaptive patterns of genetic differentiation within metapopulations, suggesting that climatic variation likely influences both demography (neutral variation) and local adaptation (adaptive variation). However, we did not observe consistent relationships between climate variables and FST across all metapopulations, underscoring the need for replication when extrapolating results from one scale to another (e.g. basin-wide to the metapopulation scale). Sensitivity analysis (leave-one-population-out) revealed consistent relationships between climate variables and FST within three metapopulations; however, these patterns were not consistent in two metapopulations likely due to small sample sizes (N = 10). These results provide correlative evidence that climatic variation has shaped the genetic structure of steelhead populations and highlight the need for replication and sensitivity analyses in land and riverscape genetics.

Relative sensitivity of five Hawaiian coral species to high temperature under high-pCO2 conditions

Coral reef ecosystems are presently undergoing decline due to anthropogenic climate change. The chief detrimental factors are increased temperature and increased pCO2. The purpose of this study was to evaluate the effect of these two stressors operating independently and in unison on the biological response of common Hawaiian reef corals. Manipulative experiments were performed using five species (Porites compressa, Pocillopora damicornis, Fungia scutaria, Montipora capitata, and Leptastrea purpurea) in a continuous-flow mesocosm system under natural sunlight conditions. Corals were grown together as a community under treatments of high temperature (2 °C above normal maximum summer temperature), high pCO2 (twice present-day conditions), and with both factors acting in unison. Control corals were grown under present-day pCO2 and at normal summer temperatures. Leptastrea purpurea proved to be an extremely hardy coral. No change in calcification or mortality occurred under treatments of high temperature, high pCO2, or combined high temperature–high pCO2. The remaining four species showed reduced calcification in the high-temperature treatment. Two species (L. purpurea and M. capitata) showed no response to increased pCO2. Also, high pCO2 ameliorated the negative effect of high temperature on the calcification rates of P. damicornis. Mortality was driven primarily by high temperature, with a negative synergistic effect in P. compressa only in the high-pCO2–high-temperature treatment. Results support the observation that biological response to temperature and pCO2 elevation is highly species-specific, so generalizations based on response of a single species might not apply to a diverse and complex coral reef community.

The Influence of Organic Material and Temperature on the Burial Tolerance of the Blue Mussel, Mytilus edulis: Considerations for the Management of Marine Aggregate Dredging.

Rationale and Experimental ApproachAggregate dredging is a growing source of anthropogenic disturbance in coastal UK waters and has the potential to impact marine systems through the smothering of benthic fauna with organically loaded screening discards. This study investigates the tolerance of the blue mussel, Mytilus edulis to such episodic smothering events using a multi-factorial design, including organic matter concentration, temperature, sediment fraction size and duration of burial as important predictor variables.Results and DiscussionMussel mortality was significantly higher in organically loaded burials when compared to control sediments after just 2 days. Particularly, M. edulis specimens under burial in fine sediment with high (1%) concentrations of organic matter experienced a significantly higher mortality rate (p<0.01) than those under coarse control aggregates. Additionally, mussels exposed to the summer maximum temperature treatment (20°C) exhibited significantly increased mortality (p<0.01) compared to those in the ambient treatment group (15°C). Total Oxygen Uptake rates of experimental aggregates were greatest (112.7 mmol m-2 day-1) with 1% organic loadings in coarse sediment at 20°C. Elevated oxygen flux rates in porous coarse sediments are likely to be a function of increased vertical migration of anaerobically liberated sulphides to the sediment-water interface. However, survival of M. edulis under bacterial mats of Beggiatoa spp. indicates the species’ resilience to sulphides and so we propose that the presence of reactive organic matter within the burial medium may facilitate bacterial growth and increase mortality through pathogenic infection. This may be exacerbated under the stable interstitial conditions in fine sediment and increased bacterial metabolism under high temperatures. Furthermore, increased temperature may impose metabolic demands upon the mussel that cannot be met during burial-induced anaerobiosis.SummaryLack of consideration for the role of organic matter and temperature during sedimentation events may lead to an overestimation of the tolerance of benthic species to smothering from dredged material.

Did summer weather factors affect gastrointestinal infection hospitalizations in New York State?

BackgroundGastrointestinal infections, a substantial public health problem worldwide, have been associated with single weather factors but the joint effect of multiple weather factors on gastrointestinal infections remains unclear. MethodsWe conducted a retrospective time-series analysis to investigate effects of weather conditions on hospitalizations for gastrointestinal infections (GIH) in New York State in July and August from 1991 to 2004. Applying generalized additive model (GAM), we evaluated the associations between daily GIH count and multiple weather factors including temperature, humidity, and precipitation (0–10 lag days), adjusting for long term trend, seasonality, and calendar effects. ResultsMaximum temperature, minimum temperature, and maximum universal apparent temperature (UAT) showed that each °C increase in temperature was significantly associated with an increase (0.70–0.96%) in daily GIH count, with the greatest impacts observed at lag 1. Extreme heat (EH: >90th percentile) (3.68% at lag 1) and precipitation (0.31% at lag 4) showed larger impacts on increases of GIH and a clear dose–response relationship for EH. Stratified analyses showed that the impacts of extreme heat on GIH tend to be greater among Hispanics, blacks, females, and those with bacterial infections. ConclusionWe found that high maximum and minimum temperature, UAT, precipitation, and extreme heat in summer significantly increased the risks of GIH in NYS. Our findings also suggest that bacteria might be a significant cause for GIH in the summer, and minority, female and those with bacterial infection may be more vulnerable to heat's effects on GIH.

Future Climate Change Scenario at Hot Semi-arid Climate of Ahmedabad (23.04°N, 72.38°E), India Based on Statistical Downscaling by LARS-WG Model

General Circulation Models (GCMs) are widely used nowadays to simulate future climate scenarios. However, present GCMs have limited skills in simulating the complex and local climate features and to provide reliable information on precipitation and temperature data which are the principal inputs to hydrologic impact assessment models. Furthermore, the outputs provided by GCMs are too coarse to be used by such hydrologic models, as they require information at much finer scales. Downscaling of GCMs output is, therefore, a necessity. Keeping this in view, the present study aimed at verifying the skills of LARS-WG, a popular downscaling tool, in downscaling weather data in hot semi-arid climate of Ahmedabad and predict and analyze the future changes of temperature (daily maximum and minimum) and precipitation based on IPCC SRA2 scenario generated by seven GCMs’ predictions for the near (2011–2030), medium (2046–2065) and far (2080–2099) future periods. For this purpose, daily rainfall, maximum and minimum temperature data for the study site Ahmedabad for 1969–2013 have been utilized. LARS-WG showed excellent skill in downscaling maximum and minimum temperature and reasonably good skill in downscaling daily rainfall data at Ahmedabad. The downscaled precipitation from the predictions of seven GCMs indicated no coherent change trends among various GCMs’ predictions of precipitation during near, medium and far future periods. Predicted rainfall in monsoon season (JJAS) based on the ensemble mean of seven GCMs showed a decrease in rainfall in near future i.e. 2011–2030 by about 2%; however, during medium future (2046–2065) it is predicted to increase and remain close to the baseline value; and during far future (2080–2099) period it is predicted to increase by about 5% compared to the baseline value. Summer maximum temperature is predicted to increase by 0.7, 2.0 and 4.0 deg. Celsius during 2011–2030, 2046–2065 and 2080–2099 respectively at the study site. Winter minimum temperature is predicted to increase by 1.0, 2.5 and 5.0 deg. Celsius during 2011–2030, 2046–2065 and 2080–2099 respectively at Ahmedabad.

Midlatitude daily summer temperatures reshaped by soil moisture under climate change

AbstractProjected changes in daily temperatures are highly model dependent, particularly in the summer midlatitudes where the spread in the response of heat waves represents a major obstacle for the design of adaptation strategies. Understanding the main reasons for such uncertainties is obviously a research priority. Here we use a set of global atmospheric simulations to assess the contribution of the soil moisture feedback to changes in the full distribution of daily maximum summer temperatures projected in the late 21st century. Results show that this feedback (i) accounts for up to one third of the mean increase in daily maximum temperatures, (ii) dominates changes in the shape of the distribution, and (iii) explains about half of the increase in the severity of heat waves over densely populated areas of the northern midlatitudes. A dedicated intercomparison project is therefore needed to assess and constrain land surface feedbacks in the new generation Earth System Models.

Adjustments of molecular key components of branchial ion and pH regulation in Atlantic cod (Gadus morhua) in response to ocean acidification and warming

Marine teleost fish sustain compensation of extracellular pH after exposure to hypercapnia by means of efficient ion and acid-base regulation. Elevated rates of ion and acid-base regulation under hypercapnia may be stimulated further by elevated temperature. Here, we characterized the regulation of transepithelial ion transporters (NKCC1, NBC1, SLC26A6, NHE1 and 2) and ATPases (Na(+)/K(+) ATPase and V-type H(+) ATPase) in gills of Atlantic cod (Gadus morhua) after 4 weeks of exposure to ambient and future PCO2 levels (550 μatm, 1200 μatm, 2200 μatm) at optimum (10 °C) and summer maximum temperature (18 °C), respectively. Gene expression of most branchial ion transporters revealed temperature- and dose-dependent responses to elevated PCO2. Transcriptional regulation resulted in stable protein expression at 10 °C, whereas expression of most transport proteins increased at medium PCO2 and 18 °C. mRNA and protein expression of distinct ion transport proteins were closely co-regulated, substantiating cellular functional relationships. Na(+)/K(+) ATPase capacities were PCO2 independent, but increased with acclimation temperature, whereas H(+) ATPase capacities were thermally compensated but decreased at medium PCO2 and 10 °C. When functional capacities of branchial ATPases were compared with mitochondrial F1Fo ATP-synthase strong correlations of F1Fo ATP-synthase and ATPase capacities generally indicate close coordination of branchial aerobic ATP demand and supply. Our data indicate physiological plasticity in the gills of cod to adjust to a warming, acidifying ocean within limits. In light of the interacting and non-linear, dose-dependent effects of both climate factors the role of these mechanisms in shaping resilience under climate change remains to be explored.