Abstract There has been a notable rise in the number of wet heatwave days across most of Asia, particularly in countries with a sizeable 65+ elderly population (e.g., China and India) and in countries with a high proportion of elderly individuals (such as Japan) during 2001-2020. The frequency of dry heatwave in Asia has been observed to increase by 0.9 day per decade, whereas the wet HTs have demonstrated a considerably more pronounced trend of 1.9 days per decade. Furthermore, the growth percentage in excess of 50% is evident in the majority of regions across Asia, including West Asia, Southeast Asia, South Asia and East Asia, which collectively account for 99% of the continent’s elderly population. Relative to the period 2001-2020, the exposure to wet heatwave is projected to increase from 1.4 times to 3.2 times in EA, from 1.6 to 13 times in WA, from 1.3 to 9 times in CA, from 1.3 to 8.4 times in SA and from 2.2 to 15.7 times in SEA from 2030 to 2100. This represents a rate of increase which is more than twice that of the dry heatwave in 2100 across most regions of Asia. The rise in temperature and the growth in the population aged 65+ are responsible for the increase in exposure to wet heatwaves, and the population effect has more contribution than the climate effect across all regions.
Gao et al. (2025) studied this question.