In the context of global warming, extreme weather and climate events have occurred frequently. In particular, compound extreme events have exerted more devastating impacts on humans and the natural environment than individual extreme events in many places. Since the beginning of 21st century, most parts of the world have experienced many severe compound extreme events and the frequency and intensity of compound extreme high temperature and drought events (CHTDE) have showed significant upward trends. In addition, compound extreme high temperature and rain events (CHTRE), which can cause landslides and other geological disasters, also have important effects on the environment. Therefore, attaching the great importance for the change in compound extreme events is the key to preventing and mitigating natural disasters and ensuring economic development and human happiness.

In recent years, human influence on compound extreme events has gradually attracted more attention. However, our understanding of compound extreme high temperature and drought/rain events is very limited, the mechanism of them is not clear. Moreover, the understanding of the changes in compound extreme high temperature and drought/rain events influenced by anthropogenic activities and natural forcings in different regions of China is still less than sufficient.

Figure 1: .Detection and attribution analysis for the severity of CHTDE and CHTRE. Best estimates of the scaling factors (dots) and their 5–95% uncertainty ranges (error bars) from (a–b) single-signal (hist-ALL, hist-AER, hist-GHG, hist-NAT, hist-ANT and hist-OA), (c–d) two-signal (hist-NAT and hist-ANT) and (e–f) four-signal (hist-AER, hist-GHG, hist-NAT, and hist-OA) analyses for (a, c, e) CHTDE and (b, d, f) CHTRE in different subregions and across China. The two dashed lines parallel to the horizontal axis represent zero and unity.

To solve the above outstanding questions, the members of the Innovation Team for Ocean-Land-Atmosphere Interaction and Global Effect of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) use a bivariate joint probability distribution between the total number of days and the maximum duration of compound extreme events to study the changes and potential causes of the severity of compound extreme high temperature and drought/rain events in China. The results indicate that the severity of compound extreme high temperature and drought events shows a significant increasing trend in most areas of China. In addition, the severity of compound extreme high temperature and rain events has increased in China, particularly in western China. They found that the increased water-holding capacity of the atmosphere and decreased relative humidity under global warming are important reasons for the increasing severity of compound extreme high temperature and drought events over China, especially in the Tibetan Plateau. For the intensified severity of compound extreme high temperature and rain events, the enhanced transient water vapor transport from the Bay of Bengal and enhanced transient convective available potential energy in western China intensified the severity of regional compound extreme high temperature and rain events under the interaction of transient dynamic lifting and transient water vapor convergence.

In addition, the quantitative optimal fingerprint method shows that the change in the severity of compound extreme high temperature and drought/rain events over China can be largely attributed to anthropogenic forcing, especially greenhouse gas forcing, which produces more than 90% of the attributable contribution to the observed compound extreme high temperature and drought/rain events (Figure 1). The authors stated that anthropogenic climate change is identified as the dominant factor affecting the severity of compound extreme high temperature and drought events in China. In addition, the historical natural forcing may be related to the interannual-to-decadal variability in the severity of compound extreme high temperature and drought/rain events. The results have important scientific significance for understanding the impact of human activities on compound extreme climate events and addressing climate change in the context of global warming.

This work entitled “Anthropogenic impact on the severity of compound extreme high temperature and drought/rain events in China” has been published in npj Climate and Atmospheric Science in July 2023. Prof. Huijun Wang and Bo Sun, from the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), and their team members carried out this study. Prof. Bo Sun is the corresponding author.

This study was jointly supported by the National Natural Science Foundation of China, National Key Research and Development Program of China, the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), and the Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disasters, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change in Nanjing University of Information Science and Technology.

Paper link:https://www.nature.com/articles/s41612-023-00413-3