Extreme Heat Research Articles

Impact of Endocrine-Disrupting Chemicals, Climate, and Air Pollution on Pregnancy Outcomes: A Scoping Review.

Environmental pollutants, including endocrine-disrupting chemicals (EDCs), air pollution, and climate change, are increasingly recognized for their potential impact on pregnancy outcomes. EDCs, found in pesticides, industrial chemicals, and personal care products, are associated with preterm birth and fetal growth restriction, primarily through hormonal interference. Air pollution, notably PM2.5, NO2, and O3, has been linked to increased rates of preterm birth, low birth weight, and stillbirth. Climate factors, such as extreme heat, elevate risks of pregnancy loss and preterm birth, with significant impacts on vulnerable populations across diverse socioeconomic and geographic regions. These exposures contribute to adverse pregnancy outcomes through mechanisms involving oxidative stress, inflammation, and endocrine disruption. The interplay among these environmental factors underscores the need for integrated, longitudinal studies to understand their combined effects on pregnancy outcomes better. Future research should focus on region-specific impacts, cumulative exposure, and policy-driven interventions to mitigate these environmental risks, especially in vulnerable populations disproportionately affected by these hazards. This scoping review synthesizes recent findings from 2019 to 2024 to highlight these associations and identify research gaps.

Atmospheric rivers cause warm winters and extreme heat events.

Atmospheric rivers (ARs) are narrow regions of intense water vapour transport in the Earth's atmosphere. These transient phenomena carry water from the subtropics to the mid-latitudes and polar regions1,2, making up the majority of polewards moisture transport3-5 and exerting control on the precipitation and water resources in many regions6,7. In addition to transporting moisture, ARs also transport heat, but the impact of this transport on global near-surface air temperatures has not yet been characterized. Here we show that seasons with more frequent ARs also have warmer than average temperatures in many mid-latitude regions, and that AR events are associated with temperature anomalies of 5-10 °C above the climatological mean. This is due to anomalous horizontal transport and convergence of sensible heat and moisture in the lower atmosphere, which increases both downward sensible heat flux and downwelling long-wave radiation at the surface. On an hourly timescale, over 70% of extreme warm-temperature anomalies occur within ARs in large portions of the mid-latitudes, and ARs are associated with moist and compound heatwaves in many regions worldwide, suggesting that consideration of ARs may improve predictive capability for certain extreme heat events. Our results demonstrate that ARs significantly impact air temperatures on a wide array of timescales, and that they may play a wider role in global energy transport than previously recognized.

Atmospheric and Surface Dynamics During Winter Warm Spells in the Southern Great Plains: Insights From the 2021 Case Study

AbstractTwo 2021 winter warm spell events experienced near record extreme surface temperatures, anomalies exceeding C, during the winter season in 2021 across the Southern Great Plains (SGP). Extreme heat during the winter season results in similar detrimental socioeconomic impacts compared to their counterpart summer heat wave events. Winter warm spell events across the SGP have been historically increasing over the last several decades, and as such, it is crucial to investigate the drivers of these extreme events. In this study, we use ERA‐5 reanalysis data to investigate the atmospheric and surface characteristics associated with these two extreme events (i.e., (a) 29 November–17 December 2021 and (b) 22 December–31 December 2021). A prolonged period of positive geopotential height anomalies amplified subsidence in combination with increased incoming solar radiation and surface heat fluxes aiding extreme surface temperatures during the first winter warm spell event. However, a more prominent atmospheric blocking high (i.e., Alaskan Ridge) initiated and intensified the extreme heat during the second winter warm spell. Increased incoming solar radiation and positive sensible heat flux due to a dry surface fostered extreme heat during the second winter warm spell event. Warm air advection throughout both winter warm spell events supported the extreme surface temperatures. Discovering potential crucial drivers to winter warm spells identifies the sources of predictability to improve prediction of these extreme heat events.

A Critical Review of Overheating Risk Assessment Criteria in International and National Regulations—Gaps and Suggestions for Improvements

The escalating environmental threat of indoor overheating, exacerbated by global climate change, urbanisation, and population growth, poses a severe risk to public health worldwide, specifically to those regions which are exposed to extreme heat events, such as Australia. This study delves into the critical issue of overheating within residential buildings, examining the existing state of knowledge on overheating criteria and reviewing overheating guidelines embedded in (a) international standards and (b) national building codes. Each regulatory document is analysed based on its underlying thermal comfort model, metric, and indices. The advantages and limitations of each document are practically discussed and for each legislative document and standard, and the quantitative measures have been reviewed, analysed, and summarised. The findings illuminate a global reliance on simplistic indices, such as indoor air temperature and operative temperature, in the existing regulatory documents. However, other critical environmental parameters, such as relative humidity, indoor air velocity, and physiological parameters including metabolic heat production and clothing insulation, are often not included. The absence of mandatory regulations for overheating criteria in residential buildings in some countries, such as in Australian homes, prompts the call for a holistic approach based on a thermal index inclusive of relevant environmental and physiological parameters to quantify heat stress exposure based on human thermal regulation. Gaps and limitations within existing guidelines are identified, and recommendations are proposed to strengthen the regulatory framework for overheating risk assessment in residential buildings. The findings hold significance for policymakers, building energy assessors, architects, and public health professionals, providing direction for the improvement of existing, and development of new, guidelines that aim to enhance indoor thermal condition and population health while ensuring energy efficiency and sustainability in the building stock.

Climate-Related Emergencies in Pregnancy.

Climate change affects human health broadly and is leading to poor population health outcomes in a number of areas. Among pregnant people specifically, it can contribute to greater risk of health complications. Certain populations are more likely to be exposed to the adverse environmental impacts of climate change, which further amplifies existing health inequities in the United States, including in maternal health. Nurses who work in emergent, acute, and critical care settings must be prepared to care for individuals who are pregnant and experiencing medical emergencies as a result of exposure to extreme heat, air pollution, natural disasters, and infectious diseases that are direct consequences of climate change. To this end, nurses must be ready to recognize, treat, and manage pregnancy complications arising from climate-related conditions, as well as provide patient education on future mitigation strategies and advocacy to reduce its harms.

Observed Variability and Future Projections of Urban Heatwaves in Romania

ABSTRACTThe crossroad between built‐up areas and extreme heat generates severe consequences on both socio‐ecological systems and the natural environment, and the cities are the most vulnerable. The impact is already significant in the present climate and it will be exacerbated under climate change in many regions, including Romania and especially its southern part. The heatwaves (HWs) are a major risk for our cities as they put constant pressure on population, infrastructure and services for several consecutive days. The urban HWs in 41 Romanian cities are analysed in terms of magnitude, amplitude, duration, number and frequency, as well as the variability of the yearly occurrence of the first and last HW events. The study focuses on the warm season (May–September) and refers to the observed variability (1961–2020) and future projections (2021–2050). The main findings reveal that the occurrence of HWs is not conditioned by geographical and climatic conditions and the cities in any region may experience public health risks associated with extreme heat. This requires permanent monitoring of the phenomena, including the present characteristics and estimating future variations according to different scenarios. Considering the increasing frequency and intensity of extreme heat events expected soon, there is a clear need for region‐specific adaptation, and policymakers should prioritise strategies to protect vulnerable people.

Recent Trends in Extreme Temperature Events Across the Contiguous United States

ABSTRACTExtreme heat events (EHEs) are becoming prevalent across the globe and are a major factor in terms of temperature‐related mortality in the United States (US). In this study, we compare trends in extreme temperature events (ETEs) across the Contiguous US, from 3 reanalysis products, namely: European Centre for Medium‐Range Weather Forecasts Reanalysis Version 5 (ERA5), Modern‐Era Retrospective Analysis for Research and Applications Version 2 (MERRA2) and North American Regional Reanalysis (NARR). We focused on the trends (1980–2022) in absolute extreme heat and cold events (ECE) as well as seasonally relative extreme heat and cold events (REHE and RECE). ETEs are defined based on a duration‐intensity metric calculated from excess apparent temperature factors, based on the exceedance of apparent temperature beyond local percentile thresholds while incorporating an acclimatisation factor. Our results show that the reanalysis data sets generally produced consistent climatology of ETEs, though with some inconsistencies in their number and spatial distribution. ETE trends in the study region are spatially heterogeneous and were more consistent between MERRA2 and ERA5. Nonetheless, all data sets agree that the frequency of EHEs is significantly increasing in the western parts of the US, whereas REHEs are significantly increasing in the southern parts. The highest increase in the frequency of EHEs occurs in southern California and Nevada, while REHE trends are maximal in Florida. RECEs are significantly decreasing more in spatial scale and magnitude than ECEs, especially towards the coastal regions. The highest decrease in RECEs is in Florida peninsula, southern California and Nevada. The data sets show inconsistency in ECE trends. Trends in excess temperature factors further indicated that extreme cold conditions are decreasing faster compared to the increasing trends of extreme heat conditions. Our findings highlight the need for improving the monitoring of ETEs across the US and for policies that mitigate the impact of ETEs on biological systems.

Enhancing solar efficiency in steppe regions: a comprehensive performance evaluation of photovoltaic systems in M’sila, Algeria

This study assesses a 10 kW grid-connected solar PV system in Algeria's harsh steppe climate in M'Sila, characterised by intense solar radiation and considerable temperature variations. High temperatures reduce photovoltaic conversion efficiency and increase thermal stresses, prompting a detailed investigation into PV systems' challenges in such environments. The research reveals that M'Sila's system generates 7,794.8 kWh annually, with an efficiency range of 16%–19.2%, peaking slightly. Unique thermal management techniques are necessary to sustain efficiency, as extreme heat causes efficiency losses of up to 20%. The levelized cost of energy (LCOE) of $0.0138 per kWh makes the system economically viable in these conditions. The investment proves worthwhile, yielding annual savings of $304. The M'Sila solar system also reduces CO₂ emissions by 4.07 tonnes per year. Algeria’s shift toward renewable energy and carbon reduction gains an additional $59.11 annually in “carbon credit” from these emissions reductions. This research supports Algeria’s renewable energy goals by guiding energy companies and decision-makers to improve efficiency and minimise environmental impact in steppe regions like M'Sila.

Construction of a composite cooling network for the mitigation of urban heat risk in Fuzhou

Climate change has intensified urban heat risks through extreme heat and heat island effects. Using Fuzhou as a case study, we conducted assessments of heat risk and cool island quality to identify core heat risk sources (CHRSs) and core cold sources (CCSs). Based on the degree of resistance to surface heat transfer, we constructed a comprehensive resistance surface. This was followed by the construction of a composite cooling network using the minimal cumulative resistance and circuit theory models, along with the identification of key nodes to enhance the protection of cool island resources and ensure network stability. Our findings revealed that the central urban area had the highest heat risk, followed by the eastern coastal areas, showing a trend of further expansion towards the southeastern coast. Relatively high-quality cool island resources were distributed in the western mountainous area. We identified 21 CHRSs and 32 CCSs. The composite cooling network included 94 heat transport corridors and 96 cool island synergy corridors, with 148 cooling nodes and 78 barrier nodes. The average land surface temperature of transport and synergy corridors was 27.89°C and 25.34°C, respectively, significantly lower than the high-risk areas (31.14°C). Transport corridors enable heat transfer from CHRSs to CCSs, while synergy corridors can achieve further cooling by enhancing the synergy among cool islands.

Observed trends in full-daytime and part-daytime thermal stress conditions in Asia

Abstract Changes in environmental thermal conditions affect thermal comfort, work performance and human health. While many studies have focused on heat and cold extremes, which are typically stressful throughout the daytime hours, fewer have examined part-daytime thermal stress conditions, where hours of thermal comfort and discomfort both occur during the daytime. Using a recently developed dataset of the Universal Thermal Climate Index (UTCI) with high spatial (10 km) and temporal (hourly) resolution, we classify daytime outdoor thermal conditions of any day into the following types: full-daytime comfortable, full-daytime stressful (subdivided into 'full-daytime cold' and 'full-daytime hot'), and part-daytime stressful (including 'part-daytime cold,' 'part-daytime cool,' 'part-daytime warm,' 'part-daytime hot,' and 'wide thermal fluctuation'). We then analyze their trends and the balance between changes in heat and cold stress over the past three decades in mid- and low-latitude Asia. Here, we demonstrate that overall daytime outdoor thermal conditions have deteriorated in both low- and mid-latitude Asia. A key feature of the changes in low-latitude regions is the substantial increase in the number of full-daytime hot days and a pronounced escalation in heat stress intensity, which may make outdoor activities during the day increasingly uncomfortable and possibly unsafe. In contrast, notable aspects of the shifts in daytime thermal conditions in mid-latitude regions include a decrease in full-daytime comfortable days (conditions ideal for longer activities such as hiking and camping), and a significant rise in part-daytime hot days, which may lead people to favour shorter activities (e.g., morning walks or neighborhood biking).

Heat wave: a new characterization in terms of energy

Heat waves (HW) are prolonged periods of excessively hot weather that can cause severe socioeconomic and environmental impacts. This study aims to evaluate the differences in stored heat and turbulent flux partitioning during a heat wave event in Mexico City, using observations from an eddy covariance tower during the period from 14 June to 21 June 2023. During this period, net radiation (Rn) and sensible heat flux (H) increased significantly, particularly from noon to evening, reflecting stable atmospheric conditions. The air temperature showed a noticeable increase in the afternoon and evening, whereas absolute humidity decreased. We found that during the heat wave, the Bowen ratio (β) increased by 80% during daylight hours and 65% over a full 24-hour period compared to the pre-heat wave period. This heat release at night prolonged warm conditions, intensifying heat stress. The partitioning of net radiation for latent heat (LE), sensible heat (H), and heat storage (ΔQs) showed significant changes; during the heat wave, 51% of Rn was allocated to H and 34% to ΔQs, compared to pre-heat wave values of 49% and 27%, respectively. This study introduces a new characterization of heat waves in terms of energy, emphasizing the significant shifts in energy flux partitioning and storage. The new characterization highlights the critical role of urban heat storage and its release in exacerbating heat stress during and after heat wave events. This approach provides a comprehensive understanding of the energy dynamics during heat waves, which is essential for developing effective mitigation strategies to combat the adverse effects of extreme heat in urban environments.

Enhancing Dimensional Stability and Environmental Durability in Delrin-Molded Parts Through Advanced Annealing Techniques

This paper presents the implementation and optimization of an advanced annealing process designed to enhance the dimensional stability, moisture resistance, and crystallinity of Delrin-molded parts for demanding outdoor applications. Delrin, a widely used acetal resin, poses unique challenges in plastic injection molding due to its natural tendency to shrink post-molding and absorb moisture, which can compromise part performance in variable environmental conditions. By introducing a high-capacity annealing oven with precise temperature and humidity control, we achieved substantial improvements in part stability and durability. This process was developed through close collaboration with customer engineering teams and our in-house experts, ensuring the final product meets strict tolerance and environmental durability requirements. Results indicate that the annealing process effectively reduces dimensional variation, decreases moisture content by 75%, and increases crystallinity by 20%, making the parts robust enough to withstand extremes of heat, cold, and humidity. This study underscores the value of high-tech annealing solutions in the plastic injection molding industry, offering a blueprint for similar applications in advanced manufacturing. Keywords: Delrin Annealing, Crystallinity Enhancement, Dimensional Stability, Moisture Resistance, Environmental Durability, Plastic Injection Molding, Advanced Manufacturing Techniques, High-Capacity Annealing Oven, Quality Engineering, Process Optimization

Interactive effects between extreme temperatures and PM2.5 on cause-specific mortality in thirteen U.S. states

The extent and robustness of the interaction between exposures to heat and ambient PM2.5 is unclear and little is known of the interaction between exposures to cold and ambient PM2.5. Clarifying these interactions, if any, is crucial due to the omnipresence of PM2.5 in the atmosphere and increasing scope and frequency of extreme temperature events. To investigate both of these interactions, we merged 6 073 575 individual-level mortality records from thirteen states spanning seventeen years with 1 km daily PM2.5 predictions from sophisticated prediction model and 1 km meteorology from Daymet V4. A time-stratified, bidirectional case-crossover design was used to control for confounding by individual-level, long-term and cyclic weekly characteristics. We fitted conditional logistic regressions with an interaction term between PM2.5 and extreme temperature events to investigate the potential interactive effects on mortality. Ambient PM2.5 exposure has the greatest effect on mortality by all internal causes in the 2 d moving average exposure window. Additionally, we found consistently synergistic interactions between a 10 μg m-3 increase in the 2 d moving average of PM2.5 and extreme heat with interaction odds ratios of 1.013 (95% CI: 1.000, 1.026), 1.024 (95% CI: 1.002, 1.046), and 1.033 (95% CI: 0.991, 1.077) for deaths by all internal causes, circulatory causes, and respiratory causes, respectively, which represent 75%, 156%, and 214% increases in the coefficient estimates for PM2.5 on those days. We also found evidence of interactions on the additive scale with corresponding relative excess risks due to interaction (RERIs) of 0.013 (95% CI: 0.003, 0.021), 0.020 (95% CI: 0.008, 0.031), and 0.017 (95% CI: -0.015, 0.036). Interactions with other PM2.5 exposure windows were more pronounced. For extreme cold, our results were suggestive of an antagonistic relationship. These results suggest that ambient PM2.5 interacts synergistically with exposure to extreme heat, yielding greater risks for mortality than only either exposure alone.

Old-growth beech forests in Germany as cool islands in a warming landscape

The climate crisis seriously threatens Central European forests and their ecosystem functions. There are indications that old-growth forests are relatively resilient and efficient in micro-climatic regulation during extreme climatic conditions. This study evaluates five well-protected old beech forests in Germany, part of a UNESCO World Heritage Site. We examined temperature dynamics and vitality in core, buffer, and border zones during hot days from 2017 to 2023, using Landsat 8 and 9 imageries to assess Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI), alongside on-site Air Temperature (AT) measurements. Our findings reveal that all five forests were impacted by recent extreme heat events, with core zones remaining cooler and more vital, followed by buffer zones. Temperature-regulating patterns varied with landscape characteristics and the surrounding matrixes. We observed a site-dependent cooling effect of the forest interior that increased with higher LST. Our study highlights the value of old-growth forests and recommends increasing effective protection around mature forests, establishing corridors between isolated patches, and creating mosaics in managed landscapes that include unmanaged areas capable of developing into old-growth ecosystems.

Riders Under the Heat: Exploring the Impact of Extreme Heat on the Integration of Bike-Sharing and Public Transportation in Shenzhen, China

Riders Under the Heat: Exploring the Impact of Extreme Heat on the Integration of Bike-Sharing and Public Transportation in Shenzhen, China

Sensitivity of mesoscale modeling to urban morphological feature inputs and implications for characterizing urban sustainability

We examine the differences in meteorological output from the Weather Research and Forecasting (WRF) model run at 270 m horizontal resolution using 10 m, 100 m and 1 km resolution 3D neighborhood morphological inputs and with no morphological inputs. We find that the spatial variability in temperature, humidity, and other meteorological variables across the city can vary with the resolution and the coverage of the 3D urban morphological input, and that larger differences occur between simulations run without 3D morphological input and those run with some type of 3D morphology. We also find that the inclusion of input-building-defined roughness length calculations would improve simulation results further. We show that these inputs produce different patterns of heat wave spatial heterogeneity across the city of Washington, DC. These findings suggest that understanding neighborhood level urban sustainability under extreme heat waves, especially for vulnerable neighborhoods, requires attention to the representation of surface terrain in numerical weather models.

It Is Normal: The Probability Distribution of Temperature Extremes

The probability of heat extremes is often estimated using the non-stationary generalized extreme value distribution (GEVD) applied to time series of annual maximum temperature. Here, this practice was assessed using a global sample of temperature time series, from reanalysis (both at the grid point and the region scale) as well as station observations. This assessment used forecast negative log-likelihood as the main performance measure, which is particularly sensitive to the most extreme heat waves. It was found that the computationally simpler normal distribution outperforms the GEVD in providing probabilistic year-ahead forecasts of temperature extremes. Given these findings, it is suggested to consider alternatives to the GEVD for assessing the risk of extreme heat.

Summertime compound heat extremes change and population heat exposure distribution in China

Amid the cumulative effects of rapid urbanization and climate warming, urban residents face serious health threats posed by heat extremes. Long-term monitoring of extreme high temperatures in cities can provide a foundational framework for mitigating the urban heat environment and enhancing the livability of residents. Utilizing long-term MODIS land surface temperature (LST) data, this study examined the fluctuations of extreme high temperatures, as well as the distribution of urban populations exposed to heat extremes and the associated health risks for urban residents across 289 prefecture-level and above cities in China from 2002 to 2020, considering natural, population and economic regional scales. The results indicated that: (1) Variations in extreme high temperatures. Extreme LST thresholds exhibited an upward trend, with the nighttime growth rate being 0.24°C/decade higher than the day. Regions characterized by higher extreme LST thresholds during the day were concentrated in Northwest and North China, while nighttime were primarily found in South Central and East China. Furthermore, regions showing higher extreme LST thresholds during the day and night were situated in well-developed cities. (2) Changes in cities exposed to heat extremes. Over the past 19 years, the majority of cities have been exposed to compound extreme high temperatures, and the number of such cities increased from 230 to 256. Notably, nearly 42% of cities have been exposed to extreme high temperatures for 15 consecutive years or longer, particularly concentrated in East China and South Central China. Developed cities were more likely to endure persistent heat extremes, especially those with a population of over 5 million and a per capita GDP of over 20,000, which have almost continuously experienced heat extreme exposure for the past 19 years. (3) Urban populations exposed to compound heat extremes. The urban population heat exposure across the country was on the rise, with the fastest growth rate of 2.91 million people per year in the nighttime, and a greater escalation in East and South Central China. Moreover, cities with lower levels of population and economic development represented the primary areas for growth0, while cities with moderate development levels showcased the slowest growth rate. (4) Health risks for urban residents. The number of urban residents dying from cardiovascular and respiratory diseases increased by 522,500, with the elderly and males accounting for a greater proportion of the increase by 234,200 and 149,800, respectively. Additionally, there existed a significant positive correlation between the deaths and heat extremes during the day and night.

Observed determinants of urban outdoor thermal exposure during hot summer and snowy winter periods in a humid continental climate

Many cities in the midlatitudes experience both extreme heat and cold, and pedestrians are exposed to thermal extremes that cause bodily stress. With growing urban populations, city design that contributes to mitigating summer heat while reducing winter cold exposure is increasingly important. Pedestrian thermal exposure depends on several microclimatic factors, including shortwave and longwave radiation absorption, which can be quantified by the mean radiant temperature (Tmrt). Limited research has been conducted on the radiative components of thermal exposure in hot, humid summers and cold, snowy winters. We gathered micrometeorological data from diverse urban sites and in multiple seasons in Guelph, Canada, using a mobile human-biometeorological weather station (MaRTy cart) that applies the six-directional method to determine Tmrt. Seasonal datasets were analysed and compared to examine the drivers of thermal exposure and recommend strategies for mitigating heat and cold stress. In summer, shade is the primary factor that reduces daytime heat exposure and it slightly increases nighttime heat exposure. Enhanced pervious ground cover is a secondary factor day and night. In winter, reduced shade alleviated daytime cold exposure, while snow cover provided daytime benefits from increased solar reflections and post-sunset penalties associated with reduced longwave radiation from low snow surface temperatures.

Extreme heat and drought did not affect interspecific interactions between dune grasses

The frequency of extreme climatic events, such as storm and heatwaves, is predicted to increase because of climate change. Understanding interactions between species in environmental extremes plays a vital role in predicting ecosystem resilience. In this study, we examined how heat and drought combined with interspecific interactions between pioneer dune builder sand couch (Thinopyrum junceiforme) and primary foredune builder marram grass (Calamagrostis arenaria) affected growth and survival of the latter species in an embryonic dune system. In a 4-week field experiment, we transplanted marram grass within sand couch patches or on bare sediment. This plant interaction treatment was combined with a compound heat and drought treatment that was simulated with greenhouses that inhibited rainfall and increased temperatures (average daily maximum temperature +4°C). Results show that the presence of sand couch significantly reduced growth (i.e., formation of new shoots, shoot and root length and aboveground biomass) of marram grass. By contrast, the heat and drought treatment had no significant effects on growth or survival of marram grass, irrespective of species interactions. The neutral response suggests that even in its early establishment marram grass is highly heat and drought resistant. Since the competitive interaction between sand couch and establishing marram grass did not change under pressure of an extreme heat and drought event, we expect that these factors do not affect embryonic dune development.