A Multi-Model Risk Assessment of Extreme Precipitation Hazards in North-Central Europe

Accelerated transformations in the European hydrological cycle during the early 21st century call for a rethinking of approaches used to detect regions susceptible to precipitation extremes. This study presents a risk map for extreme precipitation events (EPEs), categorizing areas into four risk levels: from no risk to high risk. Four risk levels were defined based on the direction, magnitude, and statistical significance of trends in extreme precipitation indices (EPIs), with the highest category representing significant positive trends within the upper percentile of the distribution. The study includes 70 years of historical data from E-OBS (1951-2020) and 13 bias-adjusted CORDEX models under two future scenarios, SSP2-4.5 and SSP5-8.5, for the period 2021-2100. To ensure reliable detection of long-term changes, the analysis employs the Mann-Kendall test with an iterative pre-whitening procedure.

The historical risk assessment derived from seven decades of E-OBS observational data shows a heterogeneous distribution across Europe. Elevated risk zones are predominantly concentrated along the western coastal regions of Scandinavia, particularly in Norway's Atlantic-facing territories. In contrast, large portions of the continental interior, including substantial areas of Poland, Germany, and the eastern Baltic states, exhibit medium to low risk levels. Under the SSP2-4.5 scenario, some areas may experience heightened risk of precipitation extremes, notably in Scandinavia, yet considerable uncertainty remains across models. Model agreement is not spatially uniform across the domain; the most pronounced disagreement occurs in southern Norway, where a relatively large area exhibits substantial variability among risk levels.

The SSP5-8.5 scenario presents a noticeable increase in risk levels, with widespread agreement among climate models. Almost the entire study domain transitions into medium to high-risk categories. This wholesale shift represents not merely an intensification of existing patterns but a fundamental reorganization of the region's extreme precipitation climatology. The changes are especially pronounced across the Scandinavian countries, with almost the entire region falling into the high-risk category.

The contrast between two emissions scenarios emphasizes the strong sensitivity of extreme precipitation patterns to greenhouse gas concentration pathways. Overall, the results emphasize the urgency of mitigation and inform adaptation planning in regions likely to face higher extreme precipitation risk.