Extreme heat events and extreme temperature have well-documented, observed impacts on health, mortality  and morbidity . AR5 described the thermoregulatory mechanisms and responses, including acclimatisation, linking heat, cold and health, and these have been further confirmed by recent studies and reviews . The health impacts of heat manifest clearly in periods of extreme heat often codified as heatwaves. For example, heatwaves across Europe , Russia , India  and Japan  resulted in significant death tolls and hospitalisations . Heat continues to pose a significant health risk due to increases in exposure, changes in the size and spatial distribution of the human population, mounting vulnerability and an increase in extreme heat events  . Some regions are already experiencing heat stress conditions approaching the upper limits of labour productivity and human survivability . These include the Persian Gulf and adjacent land areas, parts of the Indus River Valley, eastern coastal India, Pakistan, northwestern India, the shores of the Red Sea, the Gulf of California, the southern Gulf of Mexico and coastal Venezuela and Guyana .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report