Frequency Of Hot Extremes Research Articles

An analysis of observed and predicted extreme heat and precipitation trends across four pulse producing regions in North America: North Dakota, Montana, Saskatchewan, and Northeastern United States

Abstract The consumption of plant-based proteins in leu of animal proteins is the most important dietary shift that would be needed to keep the world under 2 C of warming, and this shift would require a dramatic increase in the percentage of cropland devoted to nuts and pulses (Peters et al. 2016). As the demand for plant-based proteins, like pulse crops, continues to grow, it is critical to understand the impact of climate change on crop production. In this paper, we study two climate-related stressors for pulse production in North America: extreme heat and excess moisture during harvest. Pulses must be dried on the plant before harvest, requiring a 7-day dry spell before harvest or the use of Roundup (glyphosate) to kill the plants quickly. However, little is known about the changes in frequency of hot extremes or dry spells during harvest in pulse-growing regions. We analyze climate trends using the Unprecedented Simulated Extreme Ensemble (UNSEEN) method and an analysis of the Coupled Model Intercomparison Project (CMIP6) in four pulse growing regions across North America: Montana, North Dakota, Saskatchewan, and the Northeast USA. We find that temperature extremes have increased in all regions, with extreme events 3-4 times more likely today than in 1981, increasing the risk of crop loss. August and September rainfall during the harvest months has been decreasing in the Midwestern regions and it is projected to continue to decrease in the future; however, the likelihood of a wet August in the Northeast has nearly doubled. Even with this drying trend, farmers cannot assume that they will have a 7-day consecutive dry spell that would enable natural drying of pulses without synthetic drying agents like glyphosate. Future expansion of pulse production should incorporate adaptation measures to manage extreme heat and the potential for rain events during harvest.

Increase in heat tolerance following a period of heat stress in a naturally occurring insect species.

Climate warming is the defining environmental crisis of the 21st century. Elucidating whether organisms can adapt to rapidly changing thermal environments is therefore a crucial research priority. We investigated warming effects on a native Hemipteran insect (Murgantia histrionica) that feeds on an endemic plant species (Isomeris arborea) of the California coastal sage scrub. Experiments conducted in 2009 quantified the temperature responses of juvenile maturation rates and stage-specific and cumulative survivorship. The intervening decade has seen some of the hottest years ever recorded, with increasing mean temperatures accompanied by an increase in the frequency of hot extremes. Experiments repeated in 2021 show a striking change in the bugs' temperature responses. In 2009, no eggs developed past the second nymphal stage at 33°C. In 2021, eggs developed into reproductive adults at 33°C. Upper thermal limits for maturation and survivorship have increased, along with a decrease in mortality risk with increasing age and temperature, and a decrease in the temperature sensitivity of mortality with increasing age. While we cannot exclude the possibility that other environmental factors occurring in concert could have affected our findings, the fact that all observed trait changes are in the direction of greater heat tolerance suggests that consistent exposure to extreme heat stress may at least be partially responsible for these changes. Harlequin bugs belong to the suborder Heteroptera, which contains a number of economically important pests, biological control agents and disease carriers. Their differential success in withstanding warming compared to beneficial holometabolous insects such as pollinators may exacerbate the decline of beneficial insects due to other causes (e.g. pollution and pesticides) with potentially serious consequences on both biodiversity and ecosystem functioning.

Trends in Precipitation and Air Temperature Extremes and Their Relationship with Sea Surface Temperature in the Brazilian Midwest

The Brazilian Midwest has significant spatiotemporal variability in terms of precipitation and air temperature, making it more vulnerable to the occurrence of extreme weather events. The objective of this study is to characterize the trend of extreme climatic events regarding precipitation and air temperature in the Brazilian Midwest, and to analyze their relationship with Pacific and Atlantic Sea Surface Temperature anomalies (SSTAs). We used daily precipitation and air temperature data measured at 24 conventional weather stations. Pacific and Atlantic SSTA data were obtained from the Climate Prediction Center. The frequency of hot extremes had increased, while that of cold extremes had decreased significantly, thus highlighting the consistent warming across the Brazilian Midwest. The precipitation extremes had greater variability than the temperature extremes. Precipitation intensity increased in Amazonia, with no change in annual precipitation volume. The precipitation extremes in the Brazilian Savanna, Pantanal, and the Atlantic Forest did not have a well-defined pattern but indicated a trend towards a decrease in days with intense precipitation events. In general, the Equatorial Pacific and Atlantic Ocean (TNAI and TSAI) SSTAs were negatively correlated with precipitation extreme indices and positively correlated with air temperature extreme indices in the Amazon. However, the North Atlantic SSTAs were positively correlated with precipitation and air temperature extreme indices in the Brazilian Savanna and Pantanal. In addition, the Pacific SSTAs were positively correlated with precipitation intensity in the Atlantic Forest. Thus, the variability of the trends of precipitation and air temperature extreme indices in the Brazilian Midwest was observed, and it was surmised that this measure was significantly related to Pacific and Atlantic SSTAs.

Distinct Impacts of Land Use and Land Management on Summer Temperatures

Land use has been recognized as an important anthropogenic forcing of climate change in recent studies. However, climatic effects of land management practices have been little discussed and compared to land-use impacts. As land-atmosphere interactions via surface fluxes are particularly strong during the warm season, we investigate the impacts of historical land use and present irrigation practices on summer temperatures in the Northern Hemisphere using the most recent version of Community Earth System Model. Our results suggest that historical land use leads to an overall cooling in the middle latitudes and a warming in the tropics, and the sign and magnitude of the changes in temperature depend on the type of land cover change. On the other hand, summer irrigation leads to a significant cooling over many irrigated areas due to enhanced evapotranspiration, and the local cooling is comparable to and even stronger than the land-use effects. Both land use and irrigation can also significantly influence the intensity and frequency of hot extremes. Land use shows stronger impacts during the night through ground heat flux feedback, while irrigation shows stronger impacts during the day through latent heat flux feedback. Our comparison demonstrates the importance of irrigation in local and regional climate, highlighting the necessity of considering such land management practices in future assessments of regional climate change and climate mitigation.

Contribution of mean climate to hot temperature extremes for present and future climates

The occurrence of very high temperatures (hot extremes) is often linked with negative impacts in human health, natural ecosystems and the economy (e.g., energy, water supply and agriculture). Studies have invariably shown that the intensity and frequency of hot extremes will increase in the future thus increasing their associated risks. While much progress has been made in quantifying and understanding hot temperature extremes and their future changes, there are still open questions. This paper focusses on the sources of hot extremes and their changes by applying a simple and unambiguous methodology that describes daily hot extremes as the superposition of four well known physical terms that include information on the annual mean temperature, the amplitude of the annual cycle, the diurnal temperature range and the local temperature anomaly on the day of the extreme. The methodology was applied to 30-year daily temperature records from 6 observation-based datasets and 31 atmosphere-ocean global climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The comparison between observed and simulated hot extremes shows a remarkably consistent picture where most CMIP5 models overestimate the term describing the local temperature extreme anomaly over most regions of the globe regardless of the observed dataset considered. Simultaneously, CMIP5 models show a systematic cold bias in the annual mean temperature and in the diurnal temperature range terms leading to substantial error compensation over some regions. This prompted us to define a new error estimator as the sum of errors in individual terms that appears to be much more effective at characterising model's performance compared to the traditional bias estimator. The assessment of future changes in hot extremes shows that changes are dominated by changes in annual mean temperatures with varying contributions from the other terms that strongly depend on the specific region being considered. Western Europe appears as a hot spot for extreme temperature changes (increases of ~8 ∘C by the end of the century) due to significant contributions from all decomposition terms including the summer mean anomaly, the diurnal temperature range and the daily extreme anomaly. Tropical South America also appears as a hot spot for extreme temperature changes (increases of ~7 ∘C) largely due to an increase in the daily extreme anomaly term (explaining about 30% of the full change) making this region one of the most sensitive regions in the world in terms of hot extremes. The analysis reveals that the separation of future changes according to terms describing mean, variability and tails is very sensitive to the specific way the mean component is defined including assumptions about stationarity.

Attribution of Recent Trends in Temperature Extremes over China: Role of Changes in Anthropogenic Aerosol Emissions over Asia

ABSTRACT Observations indicate large changes in temperature extremes over China during the last four decades, exhibiting as significant increases in the amplitude and frequency of hot extremes and decreases in the amplitude and frequency of cold extremes. An ensemble of transient experiments with the fully coupled atmosphere–ocean model HadGEM3-GC2, including both anthropogenic forcing and natural forcing, successfully reproduces the spatial pattern and magnitude of observed historical trends in both hot and cold extremes. The model-simulated trends in temperature extremes primarily come from the positive trends in clear-sky longwave radiation, which is mainly due to the increases in greenhouse gases (GHGs). An ensemble of sensitivity experiments with Asian anthropogenic aerosol (AA) emissions fixed at their 1970s levels tends to overestimate the trends in temperature extremes, indicating that local AA emission changes have moderated the trends in these temperature extremes over China. The recent increases in Asian AA drive cooling trends over China by inducing negative clear-sky shortwave radiation directly through the aerosol–radiation interaction, which partly offsets the strong warming effect by GHG changes. The cooling trends induced by Asian AA changes are weaker over northern China during summer, which is due to the warming effect by the positive shortwave cloud radiative effect through the AA-induced atmosphere–cloud feedback. This accounts for the observed north–south gradients of the historical trends in some temperature extremes over China, highlighting the importance of local Asian AA emission changes on spatial heterogeneity of trends in temperature extremes.

Potential to Constrain Projections of Hot Temperature Extremes

Projected changes in temperature extremes, such as regional changes in the intensity and frequency of hot extremes, differ strongly across climate models. This study shows that this disagreement can be partly explained by discrepancies in the representation of the present-day temperature distribution, motivating the evaluation of models with observations. By evaluating climate models on carefully selected metrics, the models that are more likely to be reliable for long-term projections of temperature extremes are identified. The study found that frequencies of hot extremes are likely to increase at a higher rate than the multimodel mean estimate over large parts of the Northern Hemisphere and Australia. This implies that a higher degree of adaptation is required for a given global temperature target. It also found that projected changes in the intensity of hot extremes can be constrained in several regions, including Australia, central North America, and north Asia. In many other regions, large internal variability can often hamper model evaluation. For both aspects—the intensity and the frequency of hot extremes—the total area over which the constraints can be implemented is limited by the quality and completeness of observations. Thereby, this study highlights the importance of long-term, high-quality, and easily accessible observational records for model evaluation, which are vital to ultimately reduce uncertainties in projections of temperature extremes.

Recent trends in the climate of Namaqualand, a megadiverse arid region of South Africa

Namaqualand is especially vulnerable to future climate change impacts. Using a high-resolution (0.5°x0.5°) gridded data set (CRU TS 3.1) and individual weather station data, we demonstrated that temperatures as well as frequency of hot extremes have increased across this region. Specifically, minimum temperatures have increased by 1.4 °C and maximum temperatures by 1.1 °C over the last century. Of the five weather stations analysed, two showed evidence of a significant increase in the duration of warm spells of up to 5 days per decade and a reduction in the number of cool days (TX10P) by up to 3 days per decade. In terms of rainfall, we found no clear evidence for a significant change in annual totals or the frequency or intensity of rainfall events. Seasonal trends in rainfall did, however, demonstrate some spatial variability across the region. Spatial trends in evapotranspiration obtained from the 8-day MOD16 ET product were characterised by a steepening inland-coastal gradient where areas along the coastline showed a significant increase in evapotranspiration of up to 30 mm per decade, most notably in spring and summer. The increase in temperature linked with the increases in evapotranspiration pose significant challenges for water availability in the region, but further research into changes in coastal fog is required in order for a more reliable assessment to be made. Overall, the results presented in this study provide evidence-based information for the management of climate change impacts as well as the development of appropriate adaptation responses at a local scale.

The Challenge of Post-Zionism: Alternatives to Israeli Fundamentalist PoliticsEphraim Nimni (Ed.); Zed Books 2000, hardbound, ISBN 1-85649-893-X-Hb, paperback 1-85649-894-8-Pb

Extreme climate events such as heat waves, heavy precipitation or drought can have devastating impacts on ecosystems and societies. This chapter reviews the available data for studies of, and knowledge about, global changes in a range of different climate extremes including hot and cold temperature extremes, wet and dry precipitation extremes, and high wind speeds. Observations and climate model simulations of the past century agree in showing increases in the intensity and frequency of hot extremes and decreases in the intensity and frequency of cold extremes in most regions globally. Heavy precipitation extremes have been increasing in more regions than they were decreasing, whereas meteorological drought changes depend on the region, season, and the drought indices and datasets used. Climate model projections indicate that these past tendencies are expected to continue and would even accelerate into the future in case of unabated increases in atmospheric greenhouse gas concentrations. This summary suggests that more severe impacts from hot temperature and heavy precipitation extremes can be expected in the future if no suitable adaptation and mitigation measures are taken, while stress from cold extremes is expected to become less relevant.