A recent research achievement by Associate Professor He Yongli's research group at Lanzhou University in the field of global climate change and extreme weather has been published online in Nature Communications. From a novel perspective of continuous weather processes, this study reveals the evolutionary patterns of severe flash cold events under global warming. It deepens the understanding of how cold weather risks evolve amid global warming and provides new scientific evidence for improving cold wave forecasting, refining risk assessment for extreme weather, and enhancing disaster prevention and mitigation capabilities. Associate Professor He Yongli is the first author of the paper. Professor Guan Xiaodan and Academician Huang Jianping serve as corresponding authors. PhD candidate Wang Zhanbo is the second author, and collaborators include Professor Xie Yongkun. Lanzhou University is the sole completing institution.

Figure 1 Schematic diagram illustrating circulation driving mechanisms for inter continental asymmetric changes in severe flash cold events

Global warming is steadily reducing extreme low temperature events in the conventional sense. Nevertheless, severe flash cold episodes characterized by "winter arriving overnight" still occur from time to time in recent years. Such weather brings sharp temperature drops within 24 hours, and is more likely than sustained low temperatures to trigger disasters including power supply shortages, transport disruptions and agricultural frost damage. Against ongoing global warming, how cold weather risks actually change has therefore become a key scientific concern in international climate change research.

To address this question, the Lanzhou University research team innovatively developed a new method capable of continuously tracking the full lifecycle of flash cold events. Analogous to typhoon tracking, the method analyzes the complete course of flash cold events from their formation, development and propagation to dissipation. The study shows that over the past more than 60 years, the total frequency of flash cold events across the Northern Hemisphere has not changed substantially. However, the most intense flash cold events exhibit pronounced regional divergence: they keep increasing in North America while generally decreasing over Eurasia. This indicates that global warming does not bring a uniform reduction in cold weather risks; different regions may face drastically different hazards from severe flash cold weather.

The research further uncovers the mechanisms behind such divergence. In North America, atmospheric circulations that favour the rapid southward surge of Arctic cold air have become more frequent, making severe flash cold events more probable. Over Eurasia, by contrast, pathways for southward cold air outbreaks have weakened, resulting in reduced areal coverage and shorter durations of severe flash cold events (Figure 1). The study also finds that current leading global climate models have limited skill in reproducing this regional asymmetry, mainly because they inadequately represent key atmospheric circulation processes.

Paper link: https://doi.org/10.1038/s41467-026-75094-6