A 3.5-fold increase in the synchrony of extreme precipitation and temperature events across China from 1930 to 2022.

Global warming has led to an increasing frequency of extreme climate events; however, existing studies have largely focused on individual extremes or selected pairs occurring at specific locations over relatively short time frames, with limited attention to the long-term spatial synchrony of multiple extremes across different geographic regions. This study addresses this gap by examining the synchrony of eight precipitation and temperature extreme climate events across China from 1930 to 2022, using monthly-scale data. We quantify synchrony using two indicators: the proportions of land area (LA) and population (Pop) affected by these events. Our results reveal that over the 93-year period, the annual LA increased approximately 3.5-fold, while Pop doubled, suggesting that land exposure is expanding faster than population exposure. Although underpopulated regions northwest of the Hu Huangyong Line exhibit generally lower exposure levels, they experience a higher rate of increase in land exposure compared to densely populated areas. Extreme wet and hot events drive more than 60% of the total increase in land area exposure. We also identify a significant shift in ecosystem exposure: forest lands were the most affected before 1956, but since then, grasslands have become the dominant ecosystem exposed, especially during the warmer months. This study enhances understanding of the long-term spatial synchrony of multiple extreme climate events in China and emphasizes the critical need to integrate climatic, ecological, and social vulnerabilities into adaptation strategies to effectively manage growing risks.