Summary/Abstract
Yangtze River basin (YZB) experienced record-breaking heat in the summer of 2022. In this study, the authors focused on daytime-nighttime compound heat waves, and used the magnitude index that considers both duration and intensity to investigate the risk of the 2022 extreme heat. The magnitude of heatwaves in 2022 was much larger than the historical average level, which was estimated as a 1-in-64-year event over 1979–2014 climate. Without mitigation efforts (SSP585), the record-breaking heat would emerge as normal during 2050s, and would affect ∼70% of land and projected population in the basin before global mean temperature change reaches 3°C. Such an emergence could be progressively delayed and impacts could be reduced under lower warming levels. The affected area would be 60% lesser at 2°C warming, and the emergence could be avoided by limiting warming to 1.5°C. The study’s results call for urgent mitigation efforts for reducing the risk of compound heat extremes.