NUKLEUS—A First Convection-Permitting Multimodel Ensemble for Germany: Assessment of Future Changes in Temperature and Precipitation Extremes

Abstract

This study analyzes a novel nine-member ensemble of convection-permitting regional climate simulations for Germany to assess projected changes in temperature and precipitation extremes under two future global warming levels, +2 and +3 K. The robustness of the climate change signals within the ensemble is also evaluated to ensure the reliability of the results. Throughout the twenty-first century, temperature-related extremes are projected to intensify, with nighttime extremes showing larger increases than daytime extremes. This amplification of nocturnal warming implies elevated risks to human health and ecosystems. While annual precipitation sums in Germany are projected to change only slightly and are mostly not statistically significant, the frequency and intensity of intense and very extreme precipitation events increase substantially. This change signal is particularly evident in summer, despite a predominantly decreasing seasonal mean rainfall. Such contrasting changes indicate a future characterized by generally drier summers interrupted by heavy rainfall events, with implications for both droughts occurrence and flood risk estimates. Temperature-related extremes show high robustness across almost all of Germany, whereas precipitation-related extremes exhibit greater variability, reflecting stronger natural variability and model uncertainty. The high-resolution simulations reveal added value for temperature-based indices, including more detailed spatial patterns of time averages and changes in specific areas, together with reduced uncertainty as indicated by ensemble spread and signal-to-noise ratios. These new climate model projections offer a robust scientific basis and a high potential for developing adaptation strategies tailored to small-scale landscape units.