High Sensitivity of Compound Drought and Heatwave Events to Global Warming in the Future

Compound drought and heatwave (CDHW) events have received considerable attention in recent years due to their devastating effects on human society and ecosystem. In this study, we systematically investigated the changes of CDHW events in multi-spatiotemporal scales for historical period (1951-2014) and four future scenarios (2020-2100) (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) over global land by using Coupled Model Intercomparison Project Phase 6 (CMIP6) models. The responses of the CDHW events to the changes of maximum air temperature and the climatic water balance variable are also examined. The results show that the multi-model ensembles project a significant increasing trend in CDHW characteristics over almost all global lands under SSP2-4.5, SSP3-7.0, and SSP5-8.5, especially across northern North-America, Caribbean, Mediterranean and Russian-Arctic, there is a stronger increasing trend. A significantly increasing CDHW risk will occur across most global land for the medium to long term future without aggressive adaptation and mitigation strategies. The results of path analysis suggest that temperature is the dominant factor influencing CDHW events. Additionally, higher sensitivity of CDHW events to global warming will occur in the future. Particularly, each 1 degrees C global warming increases the duration of the CDHW events by 3 days in the historical period, but by about 10 days in the future period. Overall, this study improves our understanding in the projection of CDHW events and the impacts of climate drivers to the CDHW events under various future scenarios, which could provide supports about the risk assessment, adaptation and mitigation strategies under climate change.