Compound extreme events, defined as those where multiple climate extremes converge, often result in more severe and devastating impacts than individual events. Specifically, spatially compounding events, where different climate hazards co-occur across neighboring regions, have been a focus of concern. However, studies attributing such compound extreme events to climate change have remained scarce, primarily due to methodological challenges.

 

In a recent development, Professor QIAN Cheng from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, along with his PhD student YE Yangbo, in collaboration with Dr. Emanuele Bevacqua and Professor Jakob Zscheischler from the Helmholtz Centre for Environmental Research-UFZ, Germany, unveiled a framework for attributing spatially compounding events involving two different hazards. Their innovative approach uses a storyline-probability combined model, significantly enhancing the confidence in attribution statements. Additionally, they introduced a novel constructed flow analogues method to assess the dynamic effects contributing to such events.

 

Presenting a case study on the 2020 spatially compounding heavy precipitation and heatwave event in China, the research team found that dynamic and thermodynamic factors accounted for 51% (35–67%) and 39% (18–59%) of the event's intensity, respectively. Moreover, their analysis revealed that anthropogenic climate change has increased the likelihood of similar events by at least tenfold. Projections indicate that compared to the current climate, these events may become ten and fourteen times more probable by the mid and late 21st century, respectively, under a high-emissions scenario. Notably, adopting a low-emissions scenario could reduce this likelihood to seven times more probable.

 

This study not only sheds light on the profound influence of anthropogenic climate change on high-impact compound extreme events but also underscores the urgent need for greenhouse gas emissions reduction. 

 

In the words of Professor QIAN, "Our research provides critical insights into the escalating risks posed by spatially compounding flooding and heatwave events in a changing climate. It is now more apparent than ever that urgent action is required to mitigate greenhouse gas emissions and curtail these threats."

 

Citation: Qian, C., Y. Ye, E. Bevacqua and J. Zscheischler, 2023: Human influences on spatially compounding flooding and heatwave events in China and future increasing risks. Weather Clim. Extrem., 42, 100616, https://doi.org/10.1016/j.wace.2023.100616