Projected increase in extreme heat exposure for vulnerable groups in late spring in China

Global warming advances the onset of China's heat wave season and disproportionately exposes vulnerable groups to early extreme heat risks. Despite this growing threat, a limited number of studies have examined extreme heat exposure among vulnerable groups, such as the elderly and children, during late spring (May to June). This study addresses this gap by utilising Coupled Model Intercomparison Project Phase 6 models and shared socioeconomic pathway population projections. Results reveal statistically significant ( p < 0.05) increases in the frequency and intensity of extreme heat events (daily maximum temperature ≥35 °C and ≥40 °C) during 1961–2023 late spring. According to bias-corrected model projections, such events will affect over one-third of late spring days in eastern China by 2090–2100. Projections for 2090–2100 indicate maximal exposure increases among the elderly (≥65 years old) in the Yangtze River Valley (YRV) and children (<5 years old) in South China. The YRV elderly will experience an additional 109 million person-d of heat exposure, with the exposure ratio rising from 0.2% during 1995–2014 to approximately 20%. South China's children face an additional exposure of 6.7 million person-d with a 22-fold increase in exposure ratio. Concurrently, North China will endure substantial heat exposure to temperatures ≥ 40 °C. Although climate factor remains the primary driver, population–climate combinations disproportionately amplify elderly exposure as a result of demographic shifts in heat-affected regions. These findings underscore the critical need for proactive adaptation strategies against climate-intensified extreme heat.