Large and projected increases in compound heatwaves-extreme precipitation events driven by anthropogenic emissions

Successive occurrences of compound heatwaves and extreme precipitation events (CHEPs) can amplify their adverse socioeconomic consequences. However, the role of anthropogenic forcings in driving their changes remains incompletely understood. Here, by leveraging multiple Single Model Initial-condition Large Ensembles, we systematically partition the effects of anthropogenic greenhouse gas (GHG) and aerosol (AER) emissions on the evolution of CHEPs. We find that CHEPs occur more frequently in high latitudes of the Northern hemisphere, East and Southeast Asia, North Central South America and Central Africa. CHEP frequency has significantly intensified by 1.3 times over global land areas during 1984-2014 relative to the pre-industrial period. This increase is predominantly driven by the rapid escalation of GHG emissions despite an approximately 50% offset by AER emissions and other external forcings. However, this dampening effect has weakened in recent years due to declining aerosol emissions, resulting in an accelerated global increase in CHEP occurrence. Our bivariate attribution and projection framework demonstrates that anthropogenic climate change exerts a substantially stronger influence on CHEPs in tropical regions than in other areas. Furthermore, most rare and extreme CHEPs are predominantly driven by anthropogenic GHG and are projected to increase more dramatically than normal events as global warming continues. Under a 3°C level of anthropogenic warming, CHEP frequency is projected to amplify more than fourfold across most land areas. Our findings underscore the critical need to cut fossil fuel emissions to safeguard against exacerbated compound extremes.