Science Advances – The emergency of heat and humidity too severe for human tolerance

Humans’ ability to efficiently shed heat has enabled us to range over every continent, but a wet-bulb temperature (TW) of 35°C marks our upper physiological limit. Extreme humid heat overall has more than doubled in frequency since 1979. We find the most extreme humid heat is highly localized in both space and time and is substantially underestimated in reanalysis products. Our findings underscore the serious challenge posed by humid heat that is more intense than previously reported and increasingly severe. These conditions, nearing prolonged human tolerance, have mostly occurred only for 1-to 2-hours’ duration.