Global assessment of compound drought and heatwave events and their population exposure

Climate change has exacerbated the occurrence of compound extreme events, exerting growing impacts on water resources, human societies, and ecosystems. In particular, compound drought and heatwave (CDHW) events pose a severe threat to human health. This study defined CDHW events using wet- bulb temperature (WBT) and the Standardized Precipitation Evapotranspiration Index (SPEI), and analyzed their spatiotemporal characteristics and population exposure patterns from 1940 to 2024. The results show that CDHW exhibited a significant upward trend and pronounced spatial heterogeneity across global land areas. The hotspot regions are mainly concentrated in the Russian Arctic, Western Siberia, Southeast Asia, and the Caribbean. Furthermore, the CDHW increased substantially from the historical period (1940–1979) to the recent period (1980–2024), with a global average frequency increase of 65.2%. Meanwhile, regions such as Southeastern Africa and northern South America experienced more than a twofold increase in frequency. Areas with high population exposure risk are mainly concentrated in South Asia, Southeast Asia, Southeastern Africa, West & Central Europe, and the Mediterranean. Overall, our findings provide foundational information for mitigating the risks associated with CDHW under climate change.