Increasing physical work capacity losses due to heat stress increase.

As global warming continues, hotter and more humid weather conditions become increasingly frequent, heightening population exposure to heat-stress environments. This could lead to a loss of physical work capacity (PWC loss) and result in significant economic risks. Here, we investigate the PWC loss risks and their recent changes under different heat stress environments for the period of 1985-2023. Changes in PWC loss risks on comfort days, defined by heat stress values of 20-29 °C, show a latitudinal contrast, with an overall decrease in low latitudes and an increase in high latitudes. However, they have increased everywhere on both discomfort days (30-45 °C) and dangerous days (above 45 °C), with a greater increase in the latter condition. This suggests that global warming is exacerbating the risks of PWC loss in more intense heat stress environments. Geographically, Western Europe, the Mediterranean, Siberia, the Caribbean, and northeastern South America have experienced more significant increases in PWC loss risks, exceeding 1.5 times relative to the climatological mean over the past four decades. Such changes are due more to changes in the frequency of heat stress days than to changes in the severity of PWC loss. This finding suggests that the spatio-temporal variations in meteorological aspects should be taken into account when designing policies to address PWC loss risks due to heat stress.