The study ‘Global heat stress intensification and its expanding footprint on the human population‘ uses the Copernicus Climate Change Service’s (C3S) ERA5-HEAT dataset to provide a comprehensive global-scale analysis of how heat stress has evolved since 1950.

Using the Universal Thermal Climate Index (UTCI), the study shows that hazardous heat is becoming more frequent, more intense and more widespread, with hotter nights, longer heat stress seasons and increasing numbers of people exposed to hazardous heat. Heat stress is the leading cause of weather-related mortality worldwide and exacerbates underlying illnesses such as cardiovascular, respiratory and mental health conditions. As climate warming drives more frequent and intense heat extremes, understanding how heat is experienced by the human body has become increasingly important. Trends in heatwaves are well documented, and many people worldwide are exposed to chronic heat; however, less is known about how these changes translate into trends of heat as experienced by the human population, particularly at the global scale. Authored by Rebecca Emerton, Julien Nicolas, Anna Lombardi and Claudia Di Napoli from the European Centre for Medium-Range Weather Forecasts (ECMWF), the study ‘Global heat stress intensification and its expanding footprint on the human population’ addresses this gap using the UTCI, a widely adopted biometeorological thermal stress index that accounts for temperature, humidity, wind and radiation, alongside modelling how the human body responds to the environment. Expressed as a “feels-like” temperature, the UTCI classifies thermal conditions ranging from cold stress to extreme heat stress based on their impact on the human body.

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Global study reveals how heat stress is intensifying worldwide