Climate Change and the Environment

Article information
Title: Global heat stress intensification and its expanding footprint on the human population.
First Author Last Name: Emerton, R.
Nat. Clim. Chang. (2026). https://doi.org/10.1038/s41558-026-02670-5

Abstract:
Climate warming is driving more frequent and intense heat extremes. Yet, changes in heat stress, the leading cause of weather-related mortality, remain poorly quantified at the global scale. Here, using the Universal Thermal Climate Index, we assess heat stress globally since 1950, examining daytime extremes, nocturnal heat and compound daytime–nighttime events, revealing a pronounced, multidimensional intensification. Extreme ‘feels-like’ temperatures have become more frequent on every continent, and the spatial footprint of hazardous heat has expanded, exposing previously unaffected regions. Heat stress days and tropical nights have increased, with some regions experiencing up to 50 additional heat stress days annually and an extended heat stress season. The hottest nights of the year are warming faster (0.32 °C per decade) than the hottest days (0.27 °C), and compound events are more frequent, severe and prolonged. Population exposure to dangerous heat has increased markedly, driven by intensifying heat stress in addition to population growth.

Annotation
The finding:
Heat stress is a major contributor to human morbidity and mortality, with neuropsychiatric harms especially prominent. Heat stress, including nocturnal heat, is increasing rapidly across the globe including in subtropical regions and temperate regions. Northern Africa, the Arabian Peninsula and Europe show the fastest rises.

Strength and weaknesses:
The study measured not only temperature change but “felt heat,” (Universal Climate Thermal Index or UCTI), which reflects the impact of humidity, wind and other parameters on how the body manages extreme heat. The study predicts that by 2050, every child on earth will experience extreme heat. The study provides excellent statistics and graphics that make the science easy to comprehend and clearly show the dramatic rises in temperature since the 1970’s.

Relevance:
Beyond the general demoralization and despair that many are already feeling, this study alerts us to the neuropsychiatric risks our patients will be facing. As discussed in previous publications, heat is especially lethal to those with schizophrenia. Many psychiatric medications including SSRI’s and amphetamines, not to mention drugs of abuse, increase vulnerability to heat-related morbidity and mortality. Heat, and especially nocturnal heat—which prevents restful sleep and the reparative processes that occur during sleep—have been repeatedly shown to increase aggression, suicide and acute psychiatric symptoms. Psychiatric departments and emergency services should provide their patients with visible and repeated warnings about how to prepare for heat waves and plan for increased needs during heat waves.

Article information
Title: Physiological and biological response to heat exposure in pregnancy: a systematic review and meta-analysis
PubMed ID: None—online at https://doi.org/10.1016/ j.lanplh.2026.101431
First Author Last Name: Bonell, A

Abstract:
Pregnant women are vulnerable to extreme heat due to physiological adaptations that alter thermoregulation and metabolism; however, the underlying physiological mechanisms remain inconclusive. This systematic review and meta-analysis synthesizes the effects of environmental heat on maternal, placental, and fetal physiology, identifying key biophysiological pathways.
The analysis included data from 201 906 pregnant women from 27 studies. Meta-analyses of physiological changes before and after heat exposure found mean increases of 38 beats per min (bpm) in maternal heart rate (95% CI 29·3–45·8; I2 91%; seven studies), 0·5°C in maternal core temperature (0·5–0·6; 84%; 12 studies), 1·9°C in maternal skin temperature (0·4–3·4; 99%; six studies), and 13 bpm in fetal heart rate (8·8–16·5; 78%; seven studies). On meta-regression, increased core temperature was associated with higher intensity activities and increased heat stress and inversely associated with gestational age. There were inconsistent changes in uterine and umbilical artery blood flow. However, a higher susceptibility to impaired uteroplacental blood flow was observed among pregnant women with hypertension or pre-eclampsia.
We found consistent acute physiological stress responses to heat exposure, with evidence that these responses were worse in pregnant women with pre-eclampsia. The paucity of available data highlights the need for more research to identify the underlying biological mechanisms that mediate pregnancy outcomes with high heat exposure.

Annotation
The finding:
While there are a growing number of studies demonstrating the negative impact of extreme heat on pregnancy outcomes, there are few that explore the physiology of these changes. This synthesis and meta-analysis is a first step in assessing the data. The most significant and consistent finding across 27 eligible studies was alterations to utero-placental blood flow under heat stress conditions, in women experiencing pre-eclampsia and baseline hypertension.

Strength and weaknesses:
The authors started with 3020 potentially eligible studies, but were only able to find 27 that met criteria for inclusion. Of these, there remained great heterogeneity in study type—lab simulations vs field studies; and populations studied—pregnant, elite athletes, healthy women, women with pre-eclampsia or hypertension, subsistence farmers in tropical Gambia and India. The study highlights our gaps in knowledge about potential immediate and long-term mechanisms whereby extreme heat affects mothers and their offspring, such as oxidative stress, epigenetic impacts on the fetus, inflammation and placental dysfunction.

Relevance:
Addressing the impact of climate change on pregnancy should become a research priority. Clinicians working with pregnant women can include education about managing heat to pregnant women, especially in highly impacted regions, noted above.