Heat Wave Conditions Research Articles

Thermal acclimatisation to heatwave conditions is rapid but sex-specific in wild zebra finches

Under climate change, increasing air temperature average and variability pose substantial thermal challenges to animals. While plasticity in thermoregulatory traits could potentially attenuate this impact, whether thermal acclimatisation can occur quickly enough to track weather variability in hot climates is unknown in any endotherm, and sex differences have never been tested. We investigated acclimatisation responsiveness of male and female wild zebra finches to short-term (< 2 weeks) summer temperature fluctuations in the Australian desert. Hotter weather before respirometry trials triggered a typical acclimatisation response (especially at chamber temperature Tchamb ≥ 40). However, acclimatisation occurred remarkably rapidly: metabolic rate responded within just one day, while body temperature (Tb) and evaporative cooling capacity (EHL/MHP) were best predicted by weather on the trial day; whereas evaporative water loss responded more slowly (1 week). Nonetheless, rapid acclimatisation only occurred in males, and females had higher Tb and lower EHL/MHP than males, potentially increasing hyperthermia risk. Furthermore, acclimatisation did not translate into greater acute heat tolerance (i.e. ability to tolerate Tchamb = 46 °C). Our results therefore reveal surprisingly rapid acclimatisation and even anticipatory adjustments to heat. However, with no changes in acute heat tolerance, and in females, phenotypic flexibility may provide only limited buffering against the detrimental impact of heatwaves.

Aerial exposure tolerance of juvenile flat oysters (Ostrea angasi) depends on shell length and air temperature

Oyster reefs have declined globally, impacting ecosystem structure, function, and services. The flat oyster Ostrea angasi was a dominant ecosystem engineer throughout southern Australia, forming extensive reefs now diminished to &lt;1% of historical coverage. Restoration of O. angasi has gained traction over the last decade, exclusively in subtidal habitats. However, O. angasi historically occurred in the intertidal zone, which could broaden restoration opportunities and success. There is little information quantifying factors that influence the performance of O. angasi in intertidal habitats. To test survival of O. angasi under thermal and desiccation stress experienced in intertidal habitats under winter, summer, and heatwave conditions, we emersed individuals from three age classes (1, 4, and 7 months old) at air temperatures of 10, 25, or 40°C in a series of laboratory experiments. Oysters exhibited moderate tolerance to exposure, with survival depending on interactions between emersion duration and temperature, and emersion duration and shell length. Survival broadly increased with shell length, but decreased with temperature and emersion duration. We used model predictions from the laboratory experiments to simulate intertidal survival rates at a potential restoration site in southern Australia. The simulation revealed low survival when low tides coincided with heatwaves. Field validation is needed to understand the effects of repeated tidal cycles and other biotic and abiotic influences. Our findings provide preliminary evidence for extending the restoration range of O. angasi into the low intertidal zone and can be considered when mitigating transport‐related mortality during large‐scale restoration.

Juvenile waiting stage crown-of-thorns sea stars are resilient in heatwave conditions that bleach and kill corals.

The juveniles of predatory sea stars can remain in their recruitment-nursery habitat for some time before their ontogenetic shift to the adult habitat and diet. These small juveniles are vulnerable to a range of factors with their sensitivity amplified by climate change-driven ocean warming. We investigate the thermal tolerance of the waiting stage herbivorous juveniles of the keystone coral predator, the crown-of-thorns sea star (COTS, Acanthaster sp.), in context with the degree heating weeks (DHW) model that predicts coral bleaching and mass mortality. In temperature treatments ranging from +1 to 3°C in prolonged heatwave acclimation conditions, the juveniles exhibited ~100% survival in DHW scenarios that trigger coral bleaching (4 DHW), resulting in mass mortality of corals (8 DHW) and extreme conditions well beyond those that kill corals (12 DHW). This indicates that herbivorous juvenile COTS are far more resistant to heatwave conditions than the coral prey of the adults. The juveniles exhibited higher activity (righting) and metabolic rate after weeks in increased temperature. In separate acute temperature experiments, the upper thermal limit of the juveniles was 34-36°C. In a warming world, juvenile COTS residing in their coral rubble nursery habitat will benefit from an increase in the extent of this habitat due to coral mortality. The juveniles have potential for long-term persistence as herbivores as they wait for live coral to recover before becoming coral predators, thereby serving as a proximate source of COTS outbreaks on reefs already in a tenuous state due to climate change.

Spatiotemporal distribution of air pollutants during a heat wave-induced forest fire event in Uttarakhand.

Prevailing dry conditions and rainfall deficit during the spring season in North India led to heat wave conditions which resulted in widespread and intense forest fire events in the Himalayan state of Uttarakhand during April 16-30, 2022. A total of 7589 active fires were detected by VIIRS during the second half of April 2022 compared to 1558 during the first half. The TROPOMI observed total column values of CO and NO2 increased by 4.4% and 11.7%, respectively during April 16-30, 2022 with respect to April 1-15, 2022. A noticeable increase in surface level concentration of trace gases was also observed at Dehradun. In situ measurements of CO, NOx, and O3 during April 16-30, 2022 show an increase of 133, 35, and 6%compared to previous year observations during the same period. Weather Research and Forecasting model with chemistry (WRF-Chem) is utilized to quantitatively estimate the contribution of this event on the distribution of air pollutants over this state. The model results were evaluated against ERA5 reanalysis, upper air soundings, and TROPOMI-retrieved total column density (TCD) of CO, NO2, and O3. Two simulations with (Fire) and without (NoFire) biomassburning emissions input were performed to quantify the contribution of forest fires to the concentration of trace gases and particulates. The CO, NO2, and O3 emitted/produced from forest fire over Uttarakhand during April 2022 contributed approximately 39.95, 35.73, and 9.97% to the surface concentration of respective gas. In the case of aerosols, it was around 71.20, 71.44, and 33.62% for PM2.5, PM10, and BCrespectively. The vertical profile analysis of pollutants revealed that extreme forest fire events can perturb the distribution of air pollutants from the surface up to 450 hPa.

Variability of heat stress using the UrbClim climate model in the city of Seville (Spain): mitigation proposal

Climate change is creating an increase in temperatures, which is harming the quality of life of people all over the world, particularly those with minimal financial resources. While 30% of the world’s population is now vulnerable to extreme heat, estimates show that ratio will rise to 74% in the next 20 years, according to forecasts. Using the UrbClim climate model, this study examines the space-time variability of the heat stress index (HI) in different local climate zones (LCZs), as well as how heat wave conditions might affect this index based on land use and land cover. To that end, Seville, in Southern Spain, was investigated during the summer of 2017, when it had four heat waves. The following indices were considered for each urban sub-area: Normalized Difference Vegetation, Proportion Vegetation, Normalized Difference Built, and Urban Index. The goal is to conduct a statistical analysis of the link between the aforementioned elements and the heat stress index in order to recommend mitigation and resilience techniques. Our findings showed that compact and industrial LCZs (2, 3, and 10) are less resistant to HI than open and rural regions (5, 6, B, D, and G), which are more resistant to HI due to higher vegetation rates. The heat wave condition exacerbates the HI in all LCZs. As a result, initiatives such as enhancing open space, increasing green space, or using green roofs and façades might alleviate heat stress and improve people’s quality of life.

Examining the relationship between heatwaves and fatal drowning: a case study from Queensland, Australia

BackgroundGlobally, drowning is a leading cause of injury-related harm, which is heavily impacted by environmental conditions. In Australia, fatal unintentional drowning peaks in summer, yet the impact of prolonged periods...

Prediction of maximum air temperature for defining heat wave in Rajasthan and Karnataka states of India using machine learning approach

Temperature rise, associated with global warming, has increased the severity and frequency of heat waves around the world. Rajasthan and Karnataka are two major states of India and these have been facing frequent heat waves in the past few years. The present study used machine learning approach to predict the maximum air temperature (AT) for defining the heat wave occurrences in these two states. The analysis was based on the monthly data of 13 parameters, collected from NASA's Giovanni and ERA5 reanalysis data during the summer season for the past 10-years (2013–2022). The data obtained were at different resolutions, which was resampled to 5 km × 5 km spatial resolution. Pearson's correlation and sensitivity analysis were used to check the dominant input parameters. Three machine learning approaches were used in the study: multiple linear regression (MLR), support vector regression (SVR), and random forest (RF). 3-fold cross validation was used to evaluate the model performance. The data was divided into three periods for the purpose of testing, training and validation. It was observed that the maximum AT in both states was above the limits of IMD criteria for defining heat wave occurrences. The performance of the models was evaluated using statistical metrics, comprising of root mean square error (RMSE) and coefficient of determination (R2). Good correlation of AT with land surface temperature (LST), black carbon (BC), AOD, and CO was found for both the states. AT was found to be more sensitive to the change in LST and BC compared to other parameters. The machine learning results indicated that RF outperformed MLR and SVR in predicting AT in both states. The adjusted R2 was 0.90 and 0.92, for Rajasthan and Karnataka, respectively while RMSE was 2.36% and 1.44%, for Rajasthan and Karnataka, respectively. Overall, the study shows that machine learning-based approaches can predict maximum AT for defining heat wave conditions with high accuracy. The study can have significantly applications in different fields like climate modelling studies, urban planning and infrastructure, agriculture etc. and it can help to implement appropriate measures to mitigate the adverse impacts of temperature rise.

Where and how to cool through blue infrastructure? Large lake groups to ameliorate urban overheating in a typical inland multi-lake megacity

Large lake groups have been recognized as important blue infrastructure to ameliorate urban overheating in inland megacities. Previous studies have evaluated climate regulation capabilities of large lakes on cities. However, how the specific location of lake groups affects thermal environments across extensive built-up areas through thermal and aerodynamic mechanisms remains unclear. Therefore, we conducted sensitivity experiments using the Weather Research and Forecasting (WRF) model to explore the intensity and spatial variation of air temperatures and wind fields influenced by lake groups—located in downtown areas, inner suburbs, and outer suburbs—under typical heatwave conditions in Wuhan. Results indicate that compared to similar-sized suburban lake groups, downtown lake groups exhibit higher and lower daytime lake-land differences in sensible and latent heat fluxes, respectively, resulting in greater lake cooling intensities (LCIs). Also, upwind lake groups cool more built-up areas since lake breeze circulations (LBCs) promote the spreading of lake cooling distances (LCDs). However, the development of LCIs, LCDs, and LBCs is asynchronous, with LCIs peaking around mid-morning before the generation of LBCs, and LCDs peaking in the afternoon once LBCs have developed vigorously. Moreover, we propose a planning framework integrating the cooling effects of lake groups to support cooler, healthier, and more sustainable cities.

Quantifying the statistical dependence of mid-latitude heatwave intensity and likelihood on prevalent physical drivers and climate change

Abstract. Recent heatwaves such as the 2021 Pacific Northwest heatwave have shattered temperature records across the globe. The likelihood of experiencing extreme temperature events today is already strongly increased by anthropogenic climate change, but it remains challenging to determine to what degree prevalent atmospheric and land surface conditions aggravated the intensity of a specific heatwave event. Quantifying the respective contributions is therefore paramount for process understanding but also for attribution and future projection statements conditional on the state of atmospheric circulation or land surface conditions. We here propose and evaluate a statistical framework based on extreme value theory, which enables us to learn the respective statistical relationship between extreme temperature and process variables in initial-condition large ensemble climate model simulations. Elements of statistical learning theory are implemented in order to integrate the effect of the governing regional circulation pattern. The learned statistical models can be applied to reanalysis data to quantify the relevance of physical process variables in observed heatwave events. The method also allows us to make conditional attribution statements and answer “what if” questions. For instance, how much would a heatwave intensify given the same dynamic conditions but at a different warming level? How much additional warming is needed for the same heatwave intensity to occur under average circulation conditions? Changes in the exceedance probability under varying large- and regional-scale conditions can also be assessed. We show that each additional degree of global warming increases the 7 d maximum temperature for the Pacific Northwest area by almost 2 ∘C, and likewise, we quantify the direct effect of anti-cyclonic conditions on heatwave intensity. Based on this, we find that the combined global warming and circulation effect of at least 2.9 ∘C accounts for 60 %–80 % of the 2021 excess event intensity relative to average pre-industrial heatwave conditions.

Simulated upwelling and marine heatwave events promote similar growth rates but differential domoic acid toxicity in Pseudo-nitzschia australis

Along the west coast of the United States, highly toxic Pseudo-nitzschia blooms have been associated with two contrasting regional phenomena: seasonal upwelling and marine heatwaves. While upwelling delivers cool water rich in pCO2 and an abundance of macronutrients to the upper water column, marine heatwaves instead lead to warmer surface waters, low pCO2, and reduced nutrient availability. Understanding Pseudo-nitzschia dynamics under these two conditions is important for bloom forecasting and coastal management, yet the mechanisms driving toxic bloom formation during contrasting upwelling vs. heatwave conditions remain poorly understood. To gain a better understanding of what drives Pseudo-nitzschia australis growth and toxicity during these events, multiple-driver scenario or ‘cluster’ experiments were conducted using temperature, pCO2, and nutrient levels reflecting conditions during upwelling (13 °C, 900 ppm pCO2, replete nutrients) and two intensities of marine heatwaves (19 °C or 20.5 °C, 250 ppm pCO2, reduced macronutrients). While P. australis grew equally well under both heatwave and upwelling conditions, similar to what has been observed in the natural environment, cells were only toxic in the upwelling treatment. We also conducted single-driver experiments to gain a mechanistic understanding of which drivers most impact P. australis growth and toxicity. These experiments indicated that nitrogen concentration and N:P ratio were likely the drivers that most influenced domoic acid production, while the impacts of temperature or pCO2 concentration were less pronounced. Together, these experiments may help to provide both mechanistic and holistic perspectives on toxic P. australis blooms in the dynamic and changing coastal ocean, where cells interact simultaneously with multiple altered environmental variables.

Generation of weather data for the assessment of building performances under future heatwave conditions

Heatwave weather files are needed to assess building performance under future heatwaves. This paper presents a methodology for producing a minimum set of heatwave weather files, which should be representative of the diversity of heatwaves expected in a location of interest. It is a four-step methodology. Weather projections are first collected from the CORDEX project database. Then, heatwaves are identified in the weather data. A list of independent and significant indicators is constructed to characterise the heatwaves. Samples of heatwaves are finally selected based on the list of indicators. The methodology was tested for the location of the Lyon-Saint Exupery Airport. A total of 2229 heatwaves were identified within 1260 years of weather projections. The heatwaves showed a high degree of diversity in terms of weather characteristics. The sampling process selected only 8 representative heatwaves. This number is sufficiently reduced to consider using the reduced set of heatwave weather files for assessing building performance.

Marine heatwave conditions drive carryover effects in a temperate sponge microbiome and developmental performance.

Marine heatwaves are increasingly subjecting organisms to unprecedented stressful conditions, but the biological consequences of these events are still poorly understood. Here we experimentally tested the presence of carryover effects of heatwave conditions on the larval microbiome, settlers growth rate and metamorphosis duration of the temperate sponge Crella incrustans. The microbial community of adult sponges changed significantly after ten days at 21°C. There was a relative decrease in symbiotic bacteria, and an increase in stress-associated bacteria. Sponge larvae derived from control sponges were mainly characterised by a few bacterial taxa also abundant in adults, confirming the occurrence of vertical transmission. The microbial community of sponge larvae derived from heatwave-exposed sponges showed significant increase in the endosymbiotic bacteria Rubritalea marina. Settlers derived from heatwave-exposed sponges had a greater growth rate under prolonged heatwave conditions (20 days at 21°C) compared to settlers derived from control sponges exposed to the same conditions. Moreover, settler metamorphosis was significantly delayed at 21°C. These results show, for the first time, the occurrence of heatwave-induced carryover effects across life-stages in sponges and highlight the potential role of selective vertical transmission of microbes in sponge resilience to extreme thermal events.

Use of a portable vis/NIR device to monitor the accumulation of anthocyanins during ripening in berries of ‘Sangiovese’ (Vitis vinifera L.) under heatwave conditions

Use of a portable vis/NIR device to monitor the accumulation of anthocyanins during ripening in berries of ‘Sangiovese’ (<i>Vitis vinifera</i> L.) under heatwave conditions

Temperature-Humidity-Dependent Wind Effects on Physiological Heat Strain of Moderately Exercising Individuals Reproduced by the Universal Thermal Climate Index (UTCI).

Increasing wind speed alleviates physiological heat strain; however, health policies have advised against using ventilators or fans under heat wave conditions with air temperatures above the typical skin temperature of 35 °C. Recent research, mostly with sedentary participants, suggests mitigating the effects of wind at even higher temperatures, depending on the humidity level. Our study aimed at exploring and quantifying whether such results are transferable to moderate exercise levels, and whether the Universal Thermal Climate Index (UTCI) reproduces those effects. We measured heart rates, core and skin temperatures, and sweat rates in 198 laboratory experiments completed by five young, semi-nude, heat-acclimated, moderately exercising males walking the treadmill at 4 km/h on the level for three hours under widely varying temperature-humidity combinations and two wind conditions. We quantified the cooling effect of increasing the wind speed from 0.3 to 2 m/s by fitting generalized additive models predicting the physiological heat stress responses depending on ambient temperature, humidity, and wind speed. We then compared the observed wind effects to the assessment performed by the UTCI. Increasing the wind speed lowered the physiological heat strain for air temperatures below 35 °C, but also for higher temperatures with humidity levels above 2 kPa water vapor pressure concerning heart rate and core temperature, and 3 kPa concerning skin temperature and sweat rate, respectively. The UTCI assessment of wind effects correlated positively with the observed changes in physiological responses, showing the closest agreement (r = 0.9) for skin temperature and sweat rate, where wind is known for elevating the relevant convective and evaporative heat transfer. These results demonstrate the potential of the UTCI for adequately assessing sustainable strategies for heat stress mitigation involving fans or ventilators, depending on temperature and humidity, for moderately exercising individuals.

Transcriptomic and physiological responses of a model diatom (Phaeodactylum tricornutum) to heat shock and heat selection

Diatoms are ecologically important phytoplankton as they contribute 40% of the marine primary production and play an essential role in the biogeochemical cycles of many elements. Ocean warming, as a pressing environmental stressor, can profoundly affect the population structure and ecological services of diatoms. However, the molecular mechanisms underpinning cellular and physiological changes of diatoms under heat wave and heat selection conditions remain underexplored. This study revealed the transcriptomic and physiological responses of a model diatom species P. tricornutum to ocean warming at an elevated temperature (25 °C in comparison with 20 °C) under scenarios of heat shock (∼7 days; ∼7 generations) and heat selection (∼175 days; ∼165 generations). While unchanged cell growth and reduced Fv/Fm were recorded in the heat shock treatment, significant reductions in the cell growth rate and Fv/Fm were evident in the heat selection treatment. Contents of Chl-a, carotenoid, total soluble protein, carbon (C), and nitrogen (N) increased significantly in both treatments. Transcriptomics analysis showed that elevated temperature suppressed signaling pathways related to photosynthesis but activated signaling pathways involving in fatty acid metabolism and nitrogen metabolism following the heat selection, associated with elevated substance storage and enlarged cell size. As a result, the increase of both C and N suggest that more energy was likely allocated to growth than division under ocean warming. Notably, P. tricornutum showed a higher resistance to nitrogen limitation condition after acclimating to ocean warming possibly by activation of nitrogen metabolism and uptake. P. tricornutum responded to the projected ocean warming through readjusting energy metabolism.

How Blackouts during Heat Waves Amplify Mortality and Morbidity Risk.

The recent concurrence of electrical grid failure events in time with extreme temperatures is compounding the population health risks of extreme weather episodes. Here, we combine simulated heat exposure data during historical heat wave events in three large U.S. cities to assess the degree to which heat-related mortality and morbidity change in response to a concurrent electrical grid failure event. We develop a novel approach to estimating individually experienced temperature to approximate how personal-level heat exposure changes on an hourly basis, accounting for both outdoor and building-interior exposures. We find the concurrence of a multiday blackout event with heat wave conditions to more than double the estimated rate of heat-related mortality across all three cities, and to require medical attention for between 3% (Atlanta) and more than 50% (Phoenix) of the total urban population in present and future time periods. Our results highlight the need for enhanced electrical grid resilience and support a more spatially expansive use of tree canopy and high albedo roofing materials to lessen heat exposures during compound climate and infrastructure failure events.

Using Stormwater in a Sponge City as a New Wing of Urban Water Supply—A Case Study

Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when Sponge City concepts are implemented. Thus, the concept presented here addresses existing urban neighborhoods and proposes to collect rainwater from nearby rooftops and treat it in decentral treatment units called “City Water Hubs” (CWH) equipped with modular coupled low-energy technologies to produce various customized “City Water” qualities, and store it until it can be used or distributed. A feasibility study with a focus on the campus area at the main building of the Leibniz University of Hannover, the determined rainwater qualities, and the results from investigations with two laboratory test plants provided the basis for the technical design of the pursued concept. The feasibility study showed how sufficient rainwater for irrigation purposes can be made available for the listed large university park even under extreme dry and heat wave conditions. If large portions of the roof area (11,737 m2) of the university’s main building were activated, even in a dry year with only 49.8% of the average precipitation, only 19.8% of the harvested stormwater would be needed for irrigation. The rainwater samples showed TSS concentrations of up to 7.54 mg/L, COD of up to 58.5 mg/L, and NH4 of up to 2.21 mg/L, which was in line with data reported in the literature. The treatment technologies used for the two pilot plants are proven approaches for stormwater treatment and were composed as follows: (1) gravity-driven membrane filtration (GDM) and (2) slow sand filter with integrated activated carbon (AC) layer. The treatment with both (1) and (2) clearly improved the rainwater quality. The GDM reduced turbidity by 90.4% and the Sand/AC filter by 20.4%. With regard to COD, the studies for GDM did not show a clear elimination trend; the Sand/AC filter reduced the COD by 77%. Taken together, decentralized low-energy rainwater treatment can reliably provide quality-assured City Water for any specific use. Regarding the treatment design, GDM is preferable and can be better operated with downstream UV disinfection, which might be needed to reduce the pathogenic load, e.g., for local heat control measures. The research steps presented here will pioneer the development of a city-wide rainwater harvesting infrastructure on the way of establishing stormwater as a resource for a new wing of urban water supply. The presented findings will now result in the implementation of a full-scale CHW on the campus to ensure long-term irrigation of the listed park, relieving the public drinking water supply.

Thermoregulatory and Renal Responses to Simulated Heatwaves in Younger and Older Adults

The frequency, intensity, and duration of heat waves are projected to increase in the coming decades. Older adults have impaired heat-dissipating capabilities and are at a greater risk for heat-related morbidity and mortality. Many hospitalizations and deaths in this population during heat waves are due to renal complications. Indeed, age-related reductions in kidney function, altered fluid regulation, and impaired thermoregulation, may place the elderly at an increased risk for heat-related renal complications. Purpose: Therefore, we tested the hypothesis that aging augments heatwave-induced renal stress. Methods: We assessed core temperature, mean skin temperature, whole-body sweat loss, and estimated glomerular filtration rate (eGFR) via serum creatinine in healthy older (8 Female/7 Male; 70±4 years) and younger (6 Female/7 Male; 29±4 years) adults exposed to three hours of 1) very hot and dry (DRY: 47ºC, 10% relative humidity) and 2) hot and humid (HUMID: 41ºC, 40% relative humidity) heatwave conditions on different days (random order). To simulate activities of daily living, participants performed seven 5-minute periods of light exercise (~3 METS; metabolic heat production: Old: 2.98±0.42; Young: 2.96±0.34 W/kg) dispersed across the heat exposure. Additionally, participants consumed 3 mL/kg/hr of tap-temperature water to maintain euhydration. We analyzed data from each heatwave condition independently using linear mixed effect models with main effects of time (pre and post) and group (Older and Younger) or unpaired t-tests, as appropriate. Repeated measures correlation was used to determine any relation between the change (Δ) in core temperature and Δ eGFR across both heatwave conditions. Results: Following exposure to DRY, older adults had greater increases in core temperature (Older: Δ 1.46±0.42, Younger: Δ 0.74±0.28ºC, interaction p&lt;0.01), but no difference in mean skin temperature increases (Older: Δ 2.09±1.31, Younger: Δ 1.73±0.48ºC, interaction p=0.404) or whole body sweat loss (Older: 1479±391, Younger: 1556±542 mL, p=0.661). In addition, following DRY, eGFR decreased in older but increased in younger adults (Older: Δ -4.3±5.9; Younger: Δ 4.12±4.75 mL/min/1.73 m2, interaction p&lt;0.01). Following exposure to HUMID, older adults had greater increases in core temperature (Older: Δ 1.09±0.29, Younger: Δ 0.55±0.28ºC, interaction p&lt;0.01) and mean skin temperature (Older: Δ 2.43±1.05, Younger: Δ1.37±1.13ºC, interaction p=0.018), but no difference in whole body sweat loss (Older: 979±304, Younger: 1011 ± 269 mL, p=0.774). eGFR increased in younger, but not older, adults (Older: Δ 0.30±4.01, Younger: Δ 6.16±3.37 mL/min/1.73 m2, interaction p&lt;0.01) following HUMID. There was a significant negative relation between Δ core temperature and Δ eGFR (r=-0.48, p&lt;0.01). Conclusion: These preliminary data suggest that older individuals exhibit greater increases in core temperature during heatwave exposures that may contribute to reducedrenal function. Supported by NIH R01AG069005 (CGC), F32HL154559 &amp; K01HL160772 (JCW), and F32HL154565 (LNB). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Importance of humidity for characterization and communication of dangerous heatwave conditions

Heatwaves are one of the leading causes of climate-induced mortality. Using the examples of recent heatwaves in Europe, the United States and Asia, we illustrate how the communication of dangerous conditions based on temperature maps alone can lead to insufficient societal perception of health risks. Comparison of maximum daily values of temperature with physiological heat stress indices accounting for impacts of both temperature and humidity, illustrates substantial differences in geographical extent and timing of their respective peak values during these recent events. This signals the need to revisit how meteorological heatwaves and their expected impacts are communicated. Close collaboration between climate and medical communities is needed to select the best heat stress indicators, establish them operationally, and introduce them to the public.

Sand dune shrub species prioritize hydraulic integrity over transpirational cooling during an experimental heatwave

Plant thermoregulation through transpirational cooling is important when facing heat stress and is suggested as an active mechanism to maintain lower leaf temperature during heatwaves. However, whether the role of cooling through transpiration is constrained in drought-prone habitats for the sake of hydraulic safety remains largely unknown. To evaluate the influence of plant water use characteristics on transpiration-based thermoregulation, we compared responses to natural and experimental heatwave conditions of two sand dune shrub species commonly used in dune revegetation projects but inherently differ in xylem hydraulics and water-use strategies. Salix gordejevii adopts a conservative water-use strategy and has low xylem native embolism and Caragana microphylla uses water less frugally and suffers high degrees of xylem native embolism. Under natural conditions, S. gordejevii exhibited lower transpiration levels, higher leaf temperature and had greater leaf thermotolerance with regard to cell membrane thermostability than C. microphylla. During the experimental heatwave, neither species increased cooling through transpirational water loss and maintained stable leaf water status and xylem embolism levels, suggesting that water conservation for hydraulic integrity is possibly a higher priority than transpirational cooling in sand dune shrubs experiencing heatwaves. This study provides evidence that the water-use behavior of shrubs from water-limited sand dunes prioritizes protection against water stress over heat stress.