Role of atmospheric circulation and anthropogenic forcing in the extreme 2025 European summer heatwave

Abstract

In summer 2025, an extreme heatwave propagated northeastward across Europe, sequentially affecting Southwestern (SWEU) and Northern (NEU) Europe with record-breaking durations in the 1979-2025 record. However, the roles of atmospheric circulation and anthropogenic forcing in the 2025 European high-temperature conditions remain unclear. Here we show that atmospheric circulation explains 82.5% (95% uncertainty interval: 65.0-99.0%) and 51.9% (37.0-65.2%) of the regional mean maximum temperature (Tmax) anomalies averaged over the respective heatwave periods in SWEU and NEU, respectively, based on the flow analogue method. Extreme anticyclonic circulation is associated with extreme Arctic Oscillation and British-Baikal Corridor (BBC) patterns in SWEU, and BBC and Atlantic-Eurasia patterns in NEU. Detection and attribution using Coupled Model Intercomparison Project Phase 6 simulations show that anthropogenic forcing increases the probability of exceeding the European mean June-July Tmax level observed in 2025 by a factor of 194.0 (95% confidence interval: 128.3-298.6). Greenhouse gas forcing increases the likelihood of exceeding this threshold, whereas anthropogenic aerosol forcing reduces it. These results provide insights into the roles of atmospheric circulation and anthropogenic forcing in European high-temperature conditions.