The magnitude and risk of extreme regional heatwave events in China increase rapidly under global warming

China’s ongoing scorching summer heat causes severe electricity shortages, factory shutdowns, crop failures, and heat stroke cases in its southeastern and southwestern regions. Besides the persistent and rare atmospheric circulation anomalies in the Yangtze River Valley, global warming may serve as an important driver in this unprecedented heat event.

Using an objective identification technique for distinguishing regional extreme events and a metric for measuring regional heatwave magnitude (i.e., an integrated index that accounts for heat wave intensity, duration, and spatial extent), a recent study revealed an approximate doubling in both the frequency and the magnitude of regional heatwave events observed over 1960–2018 in China. The identified top three regional heatwave events occurred in the summers of 2013, 2017, and 2003. The study also suggested that China will experience regional heatwave events with a magnitude exceeding the 2013 heat event on a regular basis by 2030 under a business-as-usual scenario (RCP8.5).

The findings, by two scientists from the Institute of Atmospheric Physics, Chinese Academy of Sciences, are published in Weather and Climate Extremes in December 2021.

"We estimated that the expected occurrence of a severe regional heat wave event (i.e., with magnitude close to or slightly larger than that of the 2013 heat wave in China) is approximately 10% for the current warming of 1 °C, corresponding to an expected event return period of 10 years. The expected occurrence is projected to increase to 30% and 55% in future 1.5 °C and 2 °C warming worlds, respectively." said lead author WANG Jun, a climate scientist at the Institute of Atmospheric Physics, Chinese Academy of Sciences.

Co-author YAN Zhongwei, a senior climatologist at the Institute of Atmospheric Physics, Chinese Academy of Sciences, further explained: "The occurrence probability of severe regional heat wave events, like the 2013 and 2022 events, will continue to increase, which has negative implications for human health, economy, and ecosystems."

Earlier researchers generally examined observed and simulated changes of heat waves at individual stations or grid points, based on which regional mean heat wave metrics and trends were estimated in a fixed area. However, A heat wave generally appears as a regional event that evolves dynamically and continuously both temporally and spatially. The current research revealed that besides heatwave intensity and duration, the spatial extent of regional heat wave events needs to be accounted for when assessing their magnitude.

Rapid rises in the frequency and magnitude of super severe regional heat wave events are projected under global warming. It means that aggressive mitigation of greenhouse gas emissions and/or robust adaptation is essential and urgent to reduce the disastrous impacts of future unprecedented regional heat wave events in China. Given the documented impacts of the 2013 heat event and the ongoing heat wave in China, the findings of this study highlight the need for efforts to strengthen the resiliencies of vulnerable sectors, communities, and regions in China to more severe regional heat wave events.