Will the 2022 compound heatwave-drought extreme over the Yangtze River Basin become Grey Rhino in the future?

The increasingly frequent and severe regional-scale compound heatwave-drought extreme events (CHDEs), driven by global warming, present formidable challenges to ecosystems, residential livelihoods, and economic conditions. However, uncertainty persists regarding the future trend of CHDEs and their insights into regional spatiotemporal heterogeneity. By integrating daily meteorological data from observations in 1961-2022 and global climate models (GCMs) based on the Shared Socioeconomic Pathways, the evolution patterns of CHDEs were compared and examined among three sub-catchments of the Yangtze River Basin, and the return periods of CHDE in 2050s and 2100s were projected. The findings indicate that the climate during the 2022 CHDE period was the warmest and driest recorded in 1961-2022, with precipitation less than 154.5 mm and a mean daily maximum temperature 3.4 degrees C higher than the average of 1981-2010, whereas the characteristics in the sub-catchments exhibited temporal and spatial variation. In July-August 2022, the most notable feature of CHDE was its extremeness since 1961, with return periods of similar to 200-year in upstream, 80-year in midstream, and 40-year in downstream, respectively. By 2050, the return periods witnessed 2022 CHDE would likely be reduced by one-third. Looking towards 2100, under the highest emission scenario of SSP585, it was projected to substantially increase the frequency of CHDEs, with return periods reduced to one-third in the upstream and downstream, as well as halved in the midstream. These findings provide valuable insights into the changing risks associated with forthcoming climate extremes, emphasizing the urgency of addressing these challenges in regional management and sustainable development.