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Extreme heat events and consequent detrimental heat-health outcomes have been increasing in recent decades and are expected to continue with future climate warming. While many indices have been created to quantify the combined atmospheric contributions to heat, few have been validated to determine how index-defined heat conditions impact human health. However, this subset of indices is likely not valid for all situations and populations nor easily understood and interpreted by health officials and the public. In this study, we compare the ability of thresholds determined from the National Weather Service’s (NWS) Heat Index (HI), the Wet Bulb Globe Temperature (WBGT), and the Universal Thermal Climate Index (UTCI) to predict the compensability of human heat stress (upper limits of heat balance) measured as part of the Pennsylvania State University’s Heat Environmental Age Thresholds (PSU HEAT) project. While the WBGT performed the best of the three indices for both minimal activities of daily living (MinAct; 83 W·m−2) and light ambulation (LightAmb; 133 W·m−2) in a cohort of young, healthy subjects, HI was likewise accurate in predicting heat stress compensability in MinAct conditions. HI was significantly correlated with subjects’ perception of temperature and humidity as well as their body core temperature, linking perception of the ambient environment with physiological responses in MinAct conditions. Given the familiarity the public has with HI, it may be better utilized in the expansion of safeguard policies and the issuance of heat warnings during extreme heat events, especially when access to engineered cooling strategies is unavailable.

More than half of the total population in China are living in cities. Especially, the people in highly developed and spatially integrated city clusters, i.e., urban agglomerations (UAs), are facing increasing human‐perceived heat stress that describes the combined effects of hot temperature, high humidity, and lowered surface wind speed. By analyzing multiple indicators over 20 major UAs across China, we demonstrate that summer heat stress has been significantly intensifying in nearly all UAs during 1971–2014. This intensification is more profound in northern than southern regions and is especially stronger in more urbanized and densely populated areas (e.g., Beijing‐Tianjin‐Hebei and the Yangtze River Delta). Based on a dynamic classification of weather stations using time‐varying land use/land cover maps, we find that urban core areas exhibit distinctly stronger increasing heat stress trends than their surrounding rural areas. On average, urbanization contributes to approximately one‐quarter of the total increase in mean heat stress over urban core areas of UAs and nearly half of the total increase in extreme heat stress events. The urbanization effect is also dependent on the geographical region within China. Urbanization tends to have stronger intensifying effects on heat stress in UAs with higher population density in low‐altitude areas, while it has a relatively weaker intensifying and even weakening effect in some arid and high‐altitude regions. Moreover, as various heat stress metrics may yield different estimations of long‐term trend and urbanization contribution, the particular choice of heat stress indicator is of critical importance for investigations on this subject matter. Plain Language Summary More and more people are living in highly developed and spatially integrated city clusters (known as urban agglomerations, UAs) and facing increasing heat risks in a warming climate. Human‐perceived heat stress describes the combined effects of hot temperature, high humidity, and lowered surface wind speed, posing severe threats to human society and the natural environment. However, how heat stress changes in UAs of fast‐urbanizing China and to what degree local urbanization contributes to these changes remains unclear. Here, we investigate the changes of heat stress over the largest 20 UAs across China by examining eight different heat stress indicators and quantify the relative contribution of local urbanization to these changes. We show that all indicators of heat stress increase in nearly all UAs of China, especially in more urbanized and populated UAs. It is estimated that, on average, local urbanization contributes to around one‐quarter of the total increase in mean heat stress in the urban core areas of UA and nearly half of the increase in extreme heat stress events. We also find that urbanization tends to have a stronger warming effect on wet and low‐altitude regions and relative weaker warming or event cooling effects on arid and high‐altitude areas. Key Points All indicators of heat stress increase in nearly all major urban agglomerations (UAs), especially in more urbanized and populated UAs On average, local urbanization contributes to ≈1/4 (1/2) of the total increase in mean (extreme) heat stress in the urban core areas of UAs Urbanization tends to have a strong warming (cooling or weak warming) effect on heat stress in wet (arid) areas and low (high) altitudes

This study aimed to assess the risk of heat stress conditions for dairy cattle in the Tigray regional state of Ethiopia under historical and future climatic conditions. The daily thermal heat index (THI) was computed for each of the 14 weather stations after quality control of the maximum and minimum temperature datasets. The calculations were performed for the historical period (1980–2023) and two future climate periods (mid-term: 2040–2069 and end-term: 2070–2099) using an ensemble of 20 global circulation models under two representative concentration pathways (RCP 4.5 and 8.5). During the historical period, the frequency of severe heat stress was 3.4% (13 days/year), predominantly occurring in the western corner of the region (39.5% of days/year). The frequency of projected severe heat stress days across the region is expected to increase to 5.4% (mid-term) and 6% (end-term) under the RCP 4.5 emission scenario. Under the RCP 8.5 scenario, the frequency is expected to rise to 6.2% (mid-term) and 9.4% (end-term). On average, there were 6–9 consecutive severe heat stress days in both the historical and future climate periods. It is crucial to emphasize that the mapping of heat stress risk in dairy cattle was carried out using THI thresholds developed elsewhere. However, it is imperative to underscore the significance of conducting local experiments to determine context-specific thresholds.

Abstract Recent studies have characterized individually experienced temperatures or individually experienced heat indices, including new exposure metrics that capture dimensions of exposure intensity, frequency, and duration. Yet, few studies have examined the personal thermal exposure in underrepresented groups, like outdoor workers, and even fewer have assessed corresponding changes in physiologic heat strain. The objective of this paper is to examine a cohort of occupationally exposed grounds and public safety workers (n = 25) to characterize their heat exposure and resulting heat strain. In addition, a secondary aim of this work is to compare individually heat index exposure (IHIE) across exposure metrics, fixed-site in situ weather stations, and raster-derived urban heat island (UHI) measurements in Charleston, SC, a humid coastal climate in the Southeastern USA. A Bland–Altman (BA) analysis was used to assess the level of agreement between the personal IHIE measurements and weather-station heat index (HI) and Urban Heat Island (UHI) measurements. Linear mixed-effect models were used to determine the association between individual risk factors and in situ weather station measurements significantly associated with IHIE measurements. Multivariable stepwise Cox proportional hazard modeling was used to identify the individual and workplace factors associated with time to heat strain in workers. We also examined the non-linear association between heat strain and exposure metrics using generalized additive models. We found significant heterogeneity in IHIE measurements across participants. We observed that time to heat strain was positively associated with a higher IHIE, older age, being male, and among Caucasian workers. Important nonlinear associations between heat strain occurrence and the intensity, frequency, and duration of personal heat metrics were observed. Lastly, our analysis found that IHIE measures were significantly similar for weather station HI, although differences were more pronounced for temperature and relative humidity measurements. Conversely, our IHIE findings were much lower than raster-derived UHI measurements. Real-time monitoring can offer important insights about unfolding temperature-health trends and emerging behaviors during thermal extreme events, which have significant potential to provide situational awareness.

This study investigates the impact of increased global warming on heat stress changes and the potential number of people exposed to heat risks over Africa. For this purpose a heat index has been computed based on an ensemble‐mean of high‐resolution regional climate model simulations from the Coordinated Output for Regional Evaluations embedded in the COordinated Regional Climate Downscaling EXperiment, under two Representative Concentration Pathways (RCPs) scenarios (RCP2.6 and RCP8.5), combined with projections of population growth developed based on the Shared Socioeconomic Pathways (SSPs) scenarios (SSP1 and SSP5). Results show that by the late 21st century, the increased global warming is expected to induce a 12‐fold increase in the area extent affected by heat stress of high‐risk level. This would result in an increase of about 10%–30% in the number of days with high‐risk heat conditions, as well as about 6%–20% in their magnitude throughout the seasonal cycle over West, Central, and North‐East Africa. Therefore, and because of the lack of adaptation and mitigation policies, the exacerbation of ambient heat conditions could contribute to the exposure of about 2–8.5 million person‐events to heat stress of high‐risk level over Burkina Faso, Ghana, Niger, and Nigeria. Furthermore, it was found that the interaction effect between the climate change and population growth seems to be the most dominant in explaining the total changes in exposure due to moderate and high heat‐related risks over all subregions of the African continent. Plain Language Summary This study investigates the impact of increased global warming on heat stress changes and the potential number of persons likely to be exposed to heat risks over Africa. Results show that by the end of the 21st century, the increased global warming is expected to induce a 12‐fold increase in the total area affected by dangerous heat conditions over the continent. This would result in an increase of about 10%–30% in the number of days with these heat conditions, as well as about 6%–20% in their magnitude throughout the seasonal cycle over West, Central and North‐East Africa. Therefore, because of the lack of adaptation and mitigation policies, the exacerbation of ambient heat conditions could contribute to the exposure of about 2–8.5 million person‐events to heat stress of high‐risk level over Burkina Faso, Ghana, Niger, and Nigeria. Since these heat events would be partly driven by interactions effects between climate change and population growth, efficient measures allowing not only to mitigate the increased greenhouse gas emissions, but also the effects of high heat on the human body must be urgently implemented on the affected countries' scale, in order to significantly decrease the vulnerability of their populations to potential heat‐related health problems. Key Points Increased global warming induces more spatially and temporally widespread extreme heat events over West, Central and North‐East Africa Populations of some West African countries are projected to be particularly exposed to moderate and high heat conditions Change in population exposure to dangerous heat categories is mainly driven by the interaction effect between climate and population growth

This study investigated children’s perceptions and adaptive behaviors related to indoor thermal conditions of classrooms in primary schools with no air-conditioning systems during both summer and winter in Dehradun City, Uttarakhand, India. Responses were collected from 5297 school children aged 6–13 years. During the measurement periods, 100% and 94% of the samples were obtained under conditions outside an 80% thermally acceptable comfort range in winter and summer, respectively. The analysis using receiver operating characteristics suggested that the students had the least sensitivity to the temperature variation for all scales of the thermal sensation vote (TSV). Approximately 95.1% of students were “very satisfied”, “satisfied”, or “slightly satisfied” with the thermal conditions under the condition of “extreme caution” or “danger” of heat risk. In contrast, adaptive thermal behaviors, such as adjusting clothing insulation ensembles, opening or closing classroom windows and doors, and utilizing ceiling fans, were found to be the most affordable options for optimizing indoor thermal comfort. Children’s reports of thermal sensations and thermal satisfaction did not correspond to the actual physical environment. This draws attention to the adequacy of applying widely used methods of TSV-based identification of the thermal comfort range in classrooms for children, especially in hot environments. The findings of this study are expected to serve as an evidence-based reference for local governments and authorities to take appropriate measures to mitigate heat risks for schoolchildren in the future.

The fecundity of fish can be utilized to predict the fish catch in the future becoming to be the most vulnerable to the negative impact of global warming. This study aimed to determine the effect of heat index on the growth and fecundity of D. macrosoma “Budloy” from the selected locations of marine waters in the Caraga region. The study was conducted at Buenavista, Agusan del Norte, Placer Surigao del Norte, and Tandag Surigao del Sur, where Shortfin scad is common. This study used Stratification random sampling to collect the samples. To calculate the present heat index of the sampling areas, present temperature, and humidity during the capture of fish samples were determined. To determine the fecundity, six parameters of D. macrosoma were calculated: length, body weight, total weight of ovary, weight of ovary samples, number of eggs, and maturity stage of D. macrosoma ovaries. In terms of the correlational analysis between heat index and length of D. macrosoma, results showed that there is a moderate positive correlation, with r = .55, p = .000, for heat index and weight, results were found to have a strong positive correlation, with r = .71, p = .000. Based on the findings on the correlation between heat index and fecundity, with r =.007, p = .959, results indicate that although there is a positive correlation between heat index and growth, there is no significant relationship between heat index and fecundity. Based on the computed values of the heat index, growth, and fecundity of D. macrosoma samples in all sites, it is concluded that Buenavista waters have the highest numerical value of the reproductive potential of D. macrosoma as the basis for predicting the fish catch in the future.

The present research aimed at analyzing temporal trends in thermal discomfort indices for a period of 46 years from 1969 to 2014 over western coastal region of India for seven urban centers during the months of pre-monsoon and monsoon seasons. Direct thermal discomfort indices employed for this purpose were thermo-hygrometric index (THI) and heat index (HI). Statistical techniques applied for obtaining temporal trends were linear regression model and Mann-Kendall (MK) rank test. Statistical significance of the obtained trends was evaluated at 95% confidence level. Sequential MK (SQ-MK) test was used for change point detection. To investigate actual incidences of thermal discomfort, daily index values were averaged for standard meteorological weeks (SMWs) over the study period and decadal percentage of thermal discomfort during SMWs was estimated. Trend analysis of selected meteorological parameters such as dry bulb temperature (DBT), wet bulb temperature (WBT), relative humidity (RH), and wind speed (WS) were investigated, which might be responsible for variation in thermal discomfort over the period. The results obtained depicted significant increase in thermal discomfort over the cities located on the southern part of west coast, while significant increase was observed during monsoon season months compared to pre-monsoon season. Decadal variation in percentage of SMWs falling in various discomfort categories was studied. At majority of the stations, moderate and high-risk SMWs have increased over the last two decades. The results of change point detection for THI and HI denoted significant increase at most of the stations after 1990s. The study validates increase in thermal discomfort vulnerability, particularly at thriving urban centers of western coastal region of India.

City thermal discomfort conditions have been exacerbated by the rapid urbanization processes in China. High-resolution urban thermal climate simulations can help us to understand urban climate features and produce better urban designs. In this paper, a single-layer urban canopy model (UCM) combined with Landsat satellite data and high-resolution meteorological forcing data was used to simulate very-high-resolution characteristics of temperature and humidity at the urban canopy level, and the heat index at the pedestrian level was also estimated. The research shows that the National center of environmental forecasting, Oregon state university, Air force and Hydrological research lab (NOAH)-UCM model can simulate the distribution of meteorological elements for different land uses in a fine and effective manner, making it an effective approach to obtaining the fundamental data for urban climate analysis. The spatial distribution pattern of urban heat islands in Suzhou is highly consistent with urban land cover fraction. High-density and medium-density urban areas are centers of urban heat islands, and the annual number of high-temperature days and heat indices over the high-density and medium-density urban areas are markedly higher than those in low-density cities and suburbs, indicating that urban development has a significant impact on the urban thermal environment.

In the context of global warming, the continued increase in the frequency of compound events—where drought and high-temperature extremes coincide—has led to severe natural disasters and substantial socio-economic losses. To systematically reveal the evolution of summer dry-heat compound events in Liaoning Province, this study constructs a whole-chain analysis framework of “identification–feature extraction–multivariate probability assessment”. Based on the Standardised Precipitation Index (SPI) and the Standardised Temperature Index (STI), we develop the Standardised Dry-Heat Index (SDHI) to identify dry-heat compound events. Run theory is applied simultaneously to extract key attributes for three types of events—drought, high temperature, and dry-heat compound events—and the Mann–Kendall test is used to detect their temporal mutation characteristics. By combining Copula functions with spatial analysis techniques, we further establish a whole-chain analysis method from “identification–feature extraction–hazard quantification”. The results show that during 1961–2020, summer drought, high-temperature, and dry-heat compound events occurred 4, 14, and 10 times, respectively, in Liaoning Province, with all three types showing a significant increase in frequency after the late 1990s. Spatially, zones of high drought intensity are mainly located in western Liaoning; the duration and severity of high temperatures are most pronounced in inland basin areas; and regions with high compound hazard intensity of dry-heat events largely coincide with urbanised areas. Climate propensity analyses further reveal that the province is experiencing an increasingly dry-heat-prone climate, with high temperatures being the dominant factor driving the enhanced hazard associated with dry-heat compound events. This study overcomes the limitations of traditional single-event analyses and provides a more accurate scientific basis for hazard assessment and zonal prevention and control of dry-heat disasters in Liaoning Province.