Advancing regional to local climate knowledge: Insights from German NUKLEUS and UDAG Consortium Projects

According to the latest assessment of the IPCC report, regional climate changes in mean climate and extremes are expected to become more widespread and pronounced. As a consequence, climate hazards are projected to increase in every region of the world leading to the necessity of developing climate adaptation and mitigation plans.  In this context, the German Federal Ministry of Education and Research (BMBF) funded several projects whose primary goal is to provide up-to-date regional and local climate projections that will subsequently form the bases for climate German adaptation strategies.

This contribution aims at illustrating ongoing research within the framework of two of these consortium projects, namely NUKLEUS (Usable Locale Climate Information for Germany) and UDAG (Updating the data basis for adaptation to climate change in Germany) to the EURO-CORDEX community. The innovative aspect of both projects lies in the creation of an unprecedented ensemble of convection permitting climate projections for “hydrological Germany" at high temporal and spatial resolution, which allows to provide information on climate change at regional and local scales.

For this purpose, NUKLEUS downscaled three global coupled models (GCMs) within the CMIP6 framework using three regional climate models (namely REMO, COSMO-CLM6 and ICON-CLM) first to the EURO-CORDEX Eur-11 domain (12 km) and subsequently to the km-scale at approximately 3 km resolution over Germany for the scenario SSP3-7.0. However, the resulting ensemble is not sufficient to provide actionable climate change information.
UDAG project aims at overcoming this limitation by downscaling a wide range of CMIP6-GCMs (6-8) using ICON-CLM first to 12 km resolution providing regional climate simulations for Europe for the scenarios SSP3-7.0 and SSP1-2.6 and then to approximately 3 km to generate climate projections specifically targeted for "hydrological Germany."

Given the shared use of common CMIP6-GCMs in the downscaling process for both projects, and considering the early stage of the UDAG project, this contribution presents initial insights from the NUKLEUS project. Biases evaluation analysis is conducted, revealing noteworthy distinctions in the RCMs at 12 km and 3 km compared to the CMIP6-GCMs. Subsequently, key metrics for extreme values statistics related to temperature and precipitation are discussed. In summary, these methods and findings serve as a preliminary groundwork for the forthcoming UDAG analysis.