Increasing risk of oppressive heatwaves over India in the future warming

Abstract

This study examines the increasing frequency of heatwaves, particularly focusing on extreme (high temperature, low humidity) and oppressive (high temperature, high humidity) heatwaves, and their impacts on human mortality. We find that both types of heatwaves are increasing, with oppressive heatwaves showing a faster rate of growth. Importantly, oppressive heatwaves are more strongly correlated with heat-stress-related human deaths than extreme heatwaves, indicating they pose a greater health risk. Using climate model simulations, we project a significant increase in the number of oppressive heatwave days under future warming scenarios. Under 1.5°C global warming, oppressive heatwaves will increase five-fold by the end of the century (2070-2100), relative to the historical period (1975-2005). Under 2°C warming, this increase rises to eight-fold, with an almost two-fold increase in oppressive heatwaves compared to the 1.5°C scenario. Extreme heatwave days, in contrast, remain relatively constant. Limiting warming to 1.5°C could reduce the likelihood of oppressive and extreme heatwaves by 44% and 25%, respectively, compared to a 2°C warming world. These findings highlight the urgent need for adaptation strategies, particularly in densely populated regions, to mitigate the health risks of rising heatwave intensity and frequency.