Global Trends in Human Thermal Stress: A Spatiotemporal Analysis from 1940 to 2020

This study presents a comprehensive spatiotemporal analysis of global thermal stress patterns from 1940 to 2020 using the Universal Thermal Climate Index (UTCI). By analyzing high-resolution hourly data from the ERA5-HEAT dataset, we examined changes in minimum, mean and maximum UTCI values across three distinct periods (1941–1970, 1966–1995, and 1991–2020). Results reveal significant warming trends, with mean UTCI increasing up to 2.5 °C across North America, Europe and Asia during 1991–2020 compared to the 1941–1970 baseline. The analysis shows marked spatial heterogeneity in thermal stress patterns, with higher latitudes experiencing reduced cold stress while tropical and subtropical regions face unprecedented increases in heat stress frequency and intensity. Central Africa has shown a concerning transformation from strong to extreme thermal stress conditions, with up to 72 additional days of extreme thermal stress annually. The study identified substantial increases in moderate thermal stress days (up to 96 additional days annually) in Central and West Africa and increased strong thermal stress days in Central Africa and South Asia (up to 48 additional days). Using Sen’s slope analysis and the Modified Mann-Kendall test, we established the statistical significance of these trends. These results highlight the importance of more focused climate adaptation approaches, especially for areas undergoing significant increases in extreme thermal stress. These findings offer important information for policy makers and urban planners to alter region-specific solutions to changing thermal stress trends.