Anthropogenic influence on the extreme drought in eastern China in 2022 and its future risk

In July–August 2022, eastern China was hit by an extreme drought event characterized by extraordinarily long persistence. The authors selected the minimum accumulated precipitation during a consecutive seven-week period during July–August (Rx49day) as the criterion to capture persistent drought extremes. Quantified by Rx49day, the 2022 drought extreme was 57.5% dryer than the climatology, and estimated as a 1-in-73-year event based on a statistical analysis. Utilizing the DAMIP (Detection and Attribution Model Intercomparison Project) runs, the study shows that anthropogenic forcing increases the occurrence probability of a 2022Drought-like event by 56%. This change is probably associated with the change in mean state over eastern China, including decreased moisture and weakened upward motion. Further, three GHG emission scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) were employed to investigate how the risk of a 2022Drought-like event will change under global warming. The projected results show that such an event is 92% less likely to occur under the low-emissions scenario, which is related to the increased background moisture and enhanced upward motion. In sharp contrast, the high-emissions scenario simulations projected an increased occurrence probability that is 79% higher than the present-day climate, probably caused by the strengthened background descending motion. The results indicate a nonlinear change in 2022Drought-like events in response to a warmer world. It is hoped that this work will provide useful information for policymakers in developing strategies that prevent eastern China from experiencing similar natural disasters.

摘要

2022年夏季中国东部地区遭遇了一次持续性极端高温干旱事件. 本文利用CMIP6检测归因比较计划 (DAMIP) 数据, 量化了人为强迫对类2022年极端干旱事件发生概率的影响, 并基于未来不同增暖情景试验给出了此类极端干旱事件的未来变化预估. 通过分析不同外强迫因子作用下此类极端干旱事件的发生概率变化, 发现人为强迫使此类极端干旱事件的发生概率提高约56%, 这主要与人为强迫下中国东部平均水汽减少和平均上升运动减弱有关. 进一步通过分析此类极端干旱事件对不同温室气体排放情景 (SSP1-2.6, SSP2-4.5, SSP5-8.5) 的响应, 发现在低排放情景下类2022年极端干旱事件的发生概率较当今气候显著下降, 这主要与中国东部平均水汽的增加和平均环流的变化有关, 而在高排放情景 (SSP5-8.5) 下, 此类极端干旱事件的发生概率较当今气候增加约79%, 这主要与高排放情景下平均下沉运动增强有关. 该研究表明, 人为强迫通过调制气候平均背景场从而引起极端事件发生频次的变化是人类活动影响极端气候事件的重要途径之一, 极端干旱事件对温室气体排放量的响应可能是非线性的.