Future warming exacerbates heatwave-ozone compound extremes in China

Exposure to concurrent heatwave and ozone pollution events poses a great threat to the health burden. Yet the impacts of future warming on such compound extremes and the associated health risks remain unclear. Here, using dynamic downscaling techniques and multi-model ensembles, we estimate excess deaths attributed to heatwave-ozone compound extremes from climate change under Shared Socioeconomic Pathways (SSPs). We find that, driven by future climate change, ozone pollution events in China are projected to grow by 58% by the middle of the century under SSP3-7.0, half of which are also heatwave days. Consequently, the heatwave-ozone compound event exposure rises by a factor of two, causing an additional 61,600 deaths nationwide. In highly polluted regions, such compound events outweigh single events by dominating the additional mortality from climate-induced increases in heat and ozone extremes. Our results emphasize the challenges of compound extremes and underscore the urgency of climate action and improved preparedness.