Global Spatiotemporal Variation and Death Burden of Compound Heatwave and Ozone Pollution Events.

Heatwaves frequently coincided with ozone to form one of the most imminent health threats under global climate change. Identifying hotspots of compound heatwave and ozone pollution events (CHOEs) has crucial significance in developing targeted mitigation strategies, which is largely unknown. We therefore performed the comprehensive global and regional analyses on the spatiotemporal variation and death burden of CHOEs during 2000-2021. In addition to CHOE exposure, we estimated its population exposure through multiplying the exposure by total population. We observed that the frequency, duration, and intensity of CHOEs and their population exposures significantly increased in most midlatitudes, particularly in the Middle East and North Africa and South Asia. The population exposures increased at an accelerating pace and were mainly driven by the CHOE itself. We estimated that the death burden of CHOEs increased over time especially in the Middle East and North Africa, with a population attributable fraction of 0.99% in 2000 to 2.01% in 2021. Our findings add novel evidence that CHOEs markedly increased and posed substantial death burdens both regionally and globally in the past two decades. This evidence highlights urgent needs to develop regional targeted mitigation and adaptation actions to reduce health risks due to CHOEs, particularly in hotspots.