Attribution of heat extremes and its health effects in Yangtze River Basin in late summer 2024

During the summer of 2024, the Yangtze River Basin (YZB) suffered from relentless heat. In particular, the late summer (from the 20th August to the 20th September) witnessed record-breaking high temperature anomalies ranging from daily to monthly timescales, reaching 5.19°C (∼4.42 standard deviations) above the 1981-2010 mean. The Sichuan Basin was the most affected areas. Our analysis suggested that such heat event would not have occurred without past human activities, and the occurrence probability of similar events is expected to increase by 91 times by the end of the 21st century under the SSP2-4.5 scenario. We further assessed population exposure to heat-related health risks during the heat event, based on the Heat Health Risk Early Warning Level recommended by China CDC. During the summer of 2024, the late summer phase suffered the most from a prolonged period of the highest-level heat health risks (level-3), with 20% of the population exposed. Simultaneously, there is a growing vulnerability of the population to all levels of heat health risks over the past decades, with exposures to both level-1 and level-2 reaching historical peaks in 2024. With a substantial increase in heat days, this increasing trend of population exposure to heat health risks is expected to continue in the future. Under the SSP2-4.5 scenario, for the level-1 heat health risk, an extra 20% of the YZB population might face such conditions by 2035 comparable to the 2024 exposure. By the 2090s, the population exposure to record-breaking heat registered in late summer of 2024 will be normal, affecting 40% of the projected population. Our study provides critical insights into the association between climate change and heat health risks from the 2024-like heat event in the YZB, highlighting the urgent need for heat health early warnings and adaptive measures.