Spatiotemporal changes in population exposure to heat stress in South Asia

Abstract

Rising temperatures and alteration of other meteorological parameters in the Indian monsoon region have exposed billions of populations in densely populated South Asia to extreme heat. This study employed high-resolution ERA5 reanalysis data for assessing spatiotemporal changes in outdoor WBGT over South Asia for the period 1979‒2021. The area affected and the population exposed to different heat levels were also estimated using LandScan population datasets. The results revealed an increase in the annual average daily mean WBGT by 0.1‒0.5°C/decade while the monsoon and pre-monsoon mean WBGT by 0.1‒0.7°C/decade over most of South Asia. The large increase in WBGT caused a rise in areas exposed to extreme heat by 56% and 66% during monsoon and pre-monsoon, respectively. Consequently, 17 million more people have been exposed to excessive heat each year. The study also revealed an increase in extremely hot days by more than six days/decade over a major part of the study area. These findings and accompanying maps can be useful to future efforts to lessen the likelihood of heat-related illness in South Asian nations, where temperature extremes have grown rapidly in recent years.