Increasing extremity and accelerating expansion of heatwaves across Eurasia

Abstract Heatwaves have increased globally under climate warming. However, quantitative assessments regarding their spatial expansion and extremity evolution at the continental scale remain limited. In this study, we used multiple datasets and a unified framework to assess long-term changes in heatwave frequency, intensity and spatial clustering across 15 reference regions of the Intergovernmental Panel on Climate Change in Eurasia from 1950 to 2023. In Eurasia, heatwaves have shifted toward more extreme conditions since the 1990s. The spatial extent of rare events, which represent the most extreme conditions exceeding the 90th percentile of the 1991–2020 baseline period, expanded most rapidly. The annual mean area affected by rare heatwaves during 2014–2023 has tripled relative to the climatological mean of the 1991–2020 baseline period. Temporally, both the frequency and intensity of heatwaves in Eurasia have accelerated since the 1990s, with most record-breaking years occurring after 2010. Spatially, heatwaves extended beyond traditional low-latitude regions. In mid- and high-latitude regions such as Northern Europe, Eastern Europe and the Russian Arctic, frequency was 1.1–1.4 times and intensity was 1.2–2.2 times higher in the recent period (1994–2023) than in the early period (1964–1993). In these regions, the occurrence probability of rare events in these areas reached 15% in the recent period. These findings highlight a shift in heatwave climatology across Eurasia under climate change and provide new insights into the evolving risk of extreme heat events.