The construction and analysis of daily temperature data series in long enough a time period is important to understand decadal to multi-decadal variability and changing trends in extreme temperature ...events. This paper reports a new analysis of extreme temperature indices over the last 140 yr in Wuhan, China, with an emphasis on changes in extreme high temperature changes. The daily temperature data from 9 stations from 1881 to 1950 and 1 modern station from 1951 to 2020 were used for the analysis. Based on the data, and the commonly used extreme temperature indices, the variations and long-term trends of extreme high temperature events in Wuhan since 1881 were analyzed. The results show that there was no clear warming trend in maximum temperature, but a quite large inter-annual and inter-decadal fluctuation. In contrast, there was a very significant increase in minimum temperature, with a large upward trend overall. The extreme temperature indices exhibit a periodic variability, and frequent extreme heat events have been experienced over the last 140 yr in Wuhan. Most extreme temperature indices did not exhibit remarkable changes during the first half of the period analyzed. However, the majority of the extreme temperature indices showed significant upward trends over the latter half of the 140 yr period. The possible causes of the observed changes in the extreme high temperature events in the different time periods are also discussed.
Proxy reconstructions from marine sediment cores indicate peak temperatures in the first half of the last and current interglacial periods (the thermal maxima of the Holocene epoch, 10,000 to 6,000 ...years ago, and the last interglacial period, 128,000 to 123,000 years ago) that arguably exceed modern warmth
. By contrast, climate models simulate monotonic warming throughout both periods
. This substantial model-data discrepancy undermines confidence in both proxy reconstructions and climate models, and inhibits a mechanistic understanding of recent climate change. Here we show that previous global reconstructions of temperature in the Holocene
and the last interglacial period
reflect the evolution of seasonal, rather than annual, temperatures and we develop a method of transforming them to mean annual temperatures. We further demonstrate that global mean annual sea surface temperatures have been steadily increasing since the start of the Holocene (about 12,000 years ago), first in response to retreating ice sheets (12 to 6.5 thousand years ago), and then as a result of rising greenhouse gas concentrations (0.25 ± 0.21 degrees Celsius over the past 6,500 years or so). However, mean annual temperatures during the last interglacial period were stable and warmer than estimates of temperatures during the Holocene, and we attribute this to the near-constant greenhouse gas levels and the reduced extent of ice sheets. We therefore argue that the climate of the Holocene differed from that of the last interglacial period in two ways: first, larger remnant glacial ice sheets acted to cool the early Holocene, and second, rising greenhouse gas levels in the late Holocene warmed the planet. Furthermore, our reconstructions demonstrate that the modern global temperature has exceeded annual levels over the past 12,000 years and probably approaches the warmth of the last interglacial period (128,000 to 115,000 years ago).
Global warming is predicted to have a negative effect on plant growth due to the damaging effect of high temperatures. In order to address the effect of high temperature environments on olive oil ...yield and quality, we compared its effect on the fruit development of five olive cultivars placed in a region noted for its high summer temperatures, with trees of the same cultivars placed in a region of relatively mild summers. We found that the effects of a high temperature environment are genotype dependent and in general, high temperatures during fruit development affected three important traits: fruit weight, oil concentration and oil quality. None of the tested cultivars exhibited complete heat stress tolerance. Final dry fruit weight at harvest of the 'Barnea' cultivar was not affected by the high temperature environment, whereas the 'Koroneiki', 'Coratina', 'Souri' and 'Picholine' cultivars exhibited decreased dry fruit weight at harvest in response to higher temperatures by 0.2, 1, 0.4 and 0.2 g respectively. The pattern of final oil concentration was also cultivar dependent, 'Barnea', 'Coratina' and 'Picholine' not being affected by the high temperature environment, whereas the 'Koroneiki' and 'Souri' cultivars showed a decreased dry fruit oil concentration at harvest under the same conditions by 15 and 8% respectively. Regarding the quality of oil produced, the 'Souri' cultivar proved more tolerant to a high temperature environment than any other of the cultivars analyzed in this study. These results suggest that different olive cultivars have developed a variety of mechanisms in dealing with high temperatures. Elucidation of the mechanism of each of these responses may open the way to development of a variety of olives broadly adapted to conditions of high temperatures.
Exposure to extreme cold or heat temperature is one leading cause of weather-associated mortality and morbidity in animals. Emerging studies demonstrate that the microbiota residing in guts act as an ...integral factor required to modulate host tolerance to cold or heat exposure, but common and unique patterns of animal-temperature associations between cold and heat have not been simultaneously examined. Therefore, we attempted to investigate the roles of gut microbiota in modulating tolerance to cold or heat exposure in mice.
The results showed that both cold and heat acutely change the body temperature of mice, but mice efficiently maintain their body temperature at conditions of chronic extreme temperatures. Mice adapt to extreme temperatures by adjusting body weight gain, food intake and energy harvest. Fascinatingly, 16 S rRNA sequencing shows that extreme temperatures result in a differential shift in the gut microbiota. Moreover, transplantation of the extreme-temperature microbiota is sufficient to enhance host tolerance to cold and heat, respectively. Metagenomic sequencing shows that the microbiota assists their hosts in resisting extreme temperatures through regulating the host insulin pathway.
Our findings highlight that the microbiota is a key factor orchestrating the overall energy homeostasis under extreme temperatures, providing an insight into the interaction and coevolution of hosts and gut microbiota.
Massive corals provide a useful archive of environmental variability, but careful testing of geochemical proxies in corals is necessary to validate the relationship between each proxy and ...environmental parameter throughout the full range of conditions experienced by the recording organisms. Here we use samples from a coral‐growth study to test the hypothesis that Sr/Ca in the coral Siderastrea siderea accurately records sea‐surface temperature (SST) in the subtropics (Florida, USA) along 350 km of reef tract. We test calcification rate, measured via buoyant weight, and linear extension (LE) rate, estimated with Alizarin Red‐S staining, as predictors of variance in the Sr/Ca records of 39 individual S. siderea corals grown at four outer‐reef locations next to in‐situ temperature loggers during two, year‐long periods. We found that corals with calcification rates < 1.7 mg cm−2 d−1 or < 1.7 mm yr−1 LE returned spuriously high Sr/Ca values, leading to a cold‐bias in Sr/Ca‐based SST estimates. The threshold‐type response curves suggest that extension rate can be used as a quality‐control indicator during sample and drill‐path selection when using long cores for SST paleoreconstruction. For our corals that passed this quality control step, the Sr/Ca‐SST proxy performed well in estimating mean annual temperature across three sites spanning 350 km of the Florida reef tract. However, there was some evidence that extreme temperature stress in 2010 (cold snap) and 2011 (SST above coral‐bleaching threshold) may have caused the corals not to record the temperature extremes. Known stress events could be avoided during modern calibrations of paleoproxies.
Plain Language Summary
Coral skeletons are used to decipher past environmental conditions in the ocean because they live for centuries and produce annual growth bands much like tree rings. Along with measuring coral growth rates in the past, coral skeletons can be chemically sampled to get even more detailed information, like past seawater temperatures. In this study we tested the validity of the strontium‐to‐calcium (Sr/Ca) temperature proxy in the Massive Starlet Coral (Siderastrea siderea) by sampling 39 corals that were grown in the ocean right next to instruments recording underwater temperature. We found that, as long as corals with very slow growth rates are avoided, the proxy performed well across an extensive region in the western Atlantic.
Key Points
The skeletal Sr/Ca ratio may not accurately reflect sea‐surface temperature when coral extension is < 1.7 mm per yr in Siderastrea siderea
The skeletal Sr/Ca ratio is validated as a temperature proxy for S. siderea at three sites across 340 km of the Florida Keys reef tract
Known coral‐stress events, possibly linked to reduced growth rates, should be avoided during modern calibrations of coral paleoproxies
Near-surface air temperature (Ta) is highly important for
modelling glacier ablation, though its spatio-temporal variability over
melting glaciers still remains largely unknown. We present a new ...dataset of
distributed Ta for three glaciers of different size in the
south-east Tibetan Plateau during two monsoon-dominated summer seasons. We
compare on-glacier Ta to ambient Ta extrapolated
from several local off-glacier stations. We parameterise the along-flowline
sensitivity of Ta on these glaciers to changes in off-glacier
temperatures (referred to as “temperature sensitivity”) and present the results
in the context of available distributed on-glacier datasets around the
world. Temperature sensitivity decreases rapidly up to 2000–3000 m
along the down-glacier flowline distance. Beyond this distance, both the
Ta on the Tibetan glaciers and global glacier datasets show
little additional cooling relative to the off-glacier temperature. In general,
Ta on small glaciers (with flowline distances <1000 m) is highly sensitive to temperature changes outside the
glacier boundary layer. The climatology of a given region can influence the
general magnitude of this temperature sensitivity, though no strong
relationships are found between along-flowline temperature sensitivity and
mean summer temperatures or precipitation. The terminus of some glaciers is
affected by other warm-air processes that increase temperature sensitivity
(such as divergent boundary layer flow, warm up-valley winds or debris/valley
heating effects) which are evident only beyond ∼70 % of the
total glacier flowline distance. Our results therefore suggest a strong role
of local effects in modulating temperature sensitivity close to the glacier
terminus, although further work is still required to explain the variability
of these effects for different glaciers.
The tiger mosquito (Aedes albopictus), vector of several emerging diseases, is expanding into more northerly latitudes as well as into higher altitudes in northern Italy. Changes in the pattern of ...distribution of the tiger mosquito may affect the potential spread of infectious diseases transmitted by this species in Europe. Therefore, predicting suitable areas of future establishment and spread is essential for planning early prevention and control strategies.
To identify the areas currently most suitable for the occurrence of the tiger mosquito in the Province of Trento, we combined field entomological observations with analyses of satellite temperature data (MODIS Land Surface Temperature: LST) and human population data. We determine threshold conditions for the survival of overwintering eggs and for adult survival using both January mean temperatures and annual mean temperatures. We show that the 0°C LST threshold for January mean temperatures and the 11°C threshold for annual mean temperatures provide the best predictors for identifying the areas that could potentially support populations of this mosquito. In fact, human population density and distance to human settlements appear to be less important variables affecting mosquito distribution in this area. Finally, we evaluated the future establishment and spread of this species in relation to predicted climate warming by considering the A2 scenario for 2050 statistically downscaled at regional level in which winter and annual temperatures increase by 1.5 and 1°C, respectively.
MODIS satellite LST data are useful for accurately predicting potential areas of tiger mosquito distribution and for revealing the range limits of this species in mountainous areas, predictions which could be extended to an European scale. We show that the observed trend of increasing temperatures due to climate change could facilitate further invasion of Ae. albopictus into new areas.
ABSTRACT
A new homogenized temperature data set called the China Homogenized Historical Temperature Dataset (CHHTD‐V1.0) has been developed, and it includes daily and monthly mean temperature series ...from 2419 national stations distributed throughout mainland China for the period from 1951 to the present. The inhomogeneities in individual station series were detected using a penalized maximum t‐test (PMT) that accounted for the first‐order autocorrelation. Detailed metadata information was applied to validate the changepoints caused by changes in local observation systems. Comparative analyses suggested that the quantile‐matching (QM) adjustments that accounted for high‐order discontinuities led to more reasonable results than the MEAN adjustments for the daily temperature series. Therefore, the QM method was applied to adjust the discontinuities caused by non‐climate changes such as changing of observing site, instrumentation and observation environments. The physical consistency among the daily maximum, mean and minimum temperatures (Tmax, Tm and Tmin) was also checked for each station. Based on the new homogenized data set, linear trends in the annual and seasonal temperature series from 1960 to 2014 were calculated. In comparison with the original data set, the homogenized data set improves the geographical consistency of the long‐term climate trends over the region. The updated nationwide mean warming rate reached 0.22 °C per 10 years for the Tmax, 0.27 °C per 10 years for the Tm and 0.38 °C per 10 years for the Tmin from 1960 to 2014, which are considerably larger than the previous estimates that were based on the more frequently used networks of a few hundred stations in China.
Remote sensing can inform agricultural knowledge of crop water use through observation of land surface temperature, which can act as an indicator of plant function and health. This study uses ...remotely sensed data to quantify thermal variability within fruit and nut orchards during an intense drought period in California's Central Valley (2013–2015). First, fractions of green vegetation (GV), non-photosynthetic vegetation (NPV), and soil were derived for a variety of crop species using visible-shortwave infrared (VSWIR) spectra imaged by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Fractional estimates were then used to select thermal endmembers for each class using simultaneously collected MODIS/ASTER Airborne Simulator (MASTER) thermal imagery and a crop species map. Expected pixel temperatures of non-stressed crop fields were then modeled, and the per-pixel difference between measured and expected temperatures was calculated as a temperature residual. Crop residuals serve to capture variability in temperature that may be attributable to differences in crop health and/or management practices. We found multiple distinct thermal classes to exist across the study site. Furthermore, crop temperatures correlated to expected crop ET rates, and temperature residuals showed correlations to changes in crop yields during the study period. Further assessment of findings revealed an increase in temperature residuals during the study period that is consistent with increasing stress, likely linked to the progression of drought. The method presented here shows utility for regional agricultural analysis of crop water use and is particularly relevant for ECOSTRESS and the upcoming Surface Biology & Geology mission.
•We use spatially coincident hyperspectral and thermal imagery to assess crop stress.•Expected pixel temperatures of non-stressed crop fields are modeled.•Hyperspectral imagery controls for thermal variability not attributable to stress.•Crop stress is quantified as the difference between the expected and measured LST.•High temperature residuals correspond to decreases in crop yields.
We use the 100-member Max Planck Institute Grand Ensemble (MPI-GE) to disentangle the contributions from colocated dynamic atmospheric conditions and local thermodynamic effects of moisture ...limitation as drivers of variability in European summer heat extremes. Using a novel extreme event definition, we find that heat extremes with respect to the evolving mean climate increase by 70% under a moderate warming scenario during the twenty-first century. With a multiple regression approach, we find that the dynamical mechanisms representing blocking and anticyclonic conditions are the main driver of variability in extreme European summer temperatures, both in past and future climates. By contrast, local thermodynamic drivers play a secondary role in explaining the total variability in extreme temperatures. We also find that considering both dynamical and thermodynamical sources of variability simultaneously is crucial. Assessing only one type of drivers leads to an overestimation of their effect on extreme temperatures, particularly when considering only thermodynamical drivers. Lastly, we find that although most past and future heat extremes occur under favorable dynamical atmospheric conditions; this occurs 10–40% less frequently over Central Europe in the twenty-first century. By contrast, heat extremes over Central Europe occur 40% more frequently under concurrent extreme moisture limitation in the twenty-first Century. Our findings highlight a new type of neutral-atmosphere, moisture-driven heat extremes, and confirm that the increase in European heat extremes and associated variability increase are dominated by the local thermodynamic effect of moisture limitation.
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