Model Projections of Increased Severity of Heat Waves in Eastern Europe

Extreme heat is investigated in a series of high‐resolution time‐slice global simulations comparing the current and late‐21st century climates. An increase in climate‐relative extreme heat is found in the region surrounding the Black Sea. Similarities between the synoptic‐scale flows in current and future heat events combined with a decrease in future summer precipitation suggests that the increased future severity stems from strengthened land‐atmosphere feedbacks driven primarily by the changes in precipitation. The resulting intensification of heat events beyond the mean warming driven by climate change could generate significant future heat hazards in vulnerable regions. Given the continental cool bias in the present‐day simulations, the resulting estimates of future extreme heat are likely to be conservative. Plain Language Summary Increases in extreme heat are a direct consequence of global warming. In some regions, however, the frequency and severity of heat waves can exceed what is expected given the rise in mean temperature alone. We examine this issue using data from a high‐resolution climate model run for 10 simulated summers under current and future (late 21st century) climate conditions. In the future simulations, extreme heat events, relative to the baseline of a much warmer climate, become more frequent and severe in a region surrounding the Black Sea. The weather patterns that lead to heat waves are very similar in the current and future climates. This similarity suggests that land‐atmosphere interactions during atmospheric heat waves amplify these events more in the future. Under warmer baseline conditions, the land dries out more rapidly during a heat event, reducing cooling from evaporation, and thus creating more severe and dangerous heat. Additionally, these model simulations are too cold over land areas, likely weakening the land‐atmosphere interactions so our projections of increased extreme heat are probably conservative. Key Points Climate‐relative extreme heat events in certain regions are substantially amplified in a set of high‐resolution future climate simulations This regional amplification of extreme heat does not depend on changes in flow regimes Results suggest amplified heat may be due to stronger regional/local land surface feedbacks, resulting in faster drying in a warmer climate