Substantial Increase in the Joint Occurrence and Human Exposure of Heatwave and High‐PM Hazards Over South Asia in the Mid‐21st Century
Extreme heat occurrence worldwide has increased in the past decades. Greenhouse gas emissions, if not abated aggressively, will lead to large increases in frequency and intensity of heat extremes. At the same time, many cities are facing severe air pollution episodes that last from days to weeks. A high‐resolution decadal‐long climate model simulation using a state‐of‐the‐science regional chemistry‐climate model shows significant increases in joint heat and haze extreme events by mid-century that would affect larger land areas.
There are significant potential health impacts due to the projected increases in the joint occurrence of the heatwave and haze hazards. These joint hazard events would have substantial increases of 175% in frequency and 79% in duration by mid-century, in contrast to the 73–76% increase for heatwave or haze events when assessed individually.
The alarming increases in the joint occurrences of extreme heat and haze events in just a few decades pose great challenges to adaptation. This increasing hazard depends on the magnitude of future warming. For example, under a lower emission pathway, the frequency of joint heat and haze extremes will only increase by 58% compared to an increase of 175% in a higher emission scenario.