Doubling the frequency of extreme short-duration summer rainfall events in the European Alps with regional warming

Convective summer rainfall in the European Alps frequently triggers hazardous events, including flash floods and debris flows, with severe implications for infrastructure and communities. Future climate warming is projected to exacerbate these risks by intensifying extreme short-duration rainfall. This study explores how such intensification might considerably increase the frequency of extreme 10-minute and hourly rainfall in the Alpine region. Using the physically-based TENAX model, which integrates temperature-dependent scaling with rainfall intensity distribution, we identified significant changes in rainfall return periods. The model combines observed temperature-rainfall relationships with a Monte Carlo approach to project future extremes under various warming scenarios, leveraging outputs from 17 regional climate models provided by the EURO-CORDEX project. Using the model, we found that the frequency of what are today’s 50-year rainfall events over 299 alpine stations is projected to double when regional temperature increases by 2°C. Additionally, the results reveal that the projected intensification is not uniform across the region, with high-altitude stations showing an even greater increase in extreme rainfall frequency compared to lower elevations. This spatial variability underscores the complexity of addressing climate impacts in mountainous terrains. These findings emphasize the urgent need for adaptive measures tailored to elevation. Our study highlights the necessity of revising infrastructure standards and enhancing risk management strategies to prepare for a future with more frequent extreme rainfall events.