Evaluation of EURO-CORDEX Regional Climate Models: Model Subselection for Switzerland

Accurate projections of regional climate change are crucial for understanding future risks and formulating effective adaptation strategies. Switzerland's complex topography and diverse climate pose challenges to obtaining reliable modeling of its future climate. This study evaluates the EURO-CORDEX regional climate models (RCMs) to identify a subset of models best suited for temperature and precipitation projections in Switzerland. The evaluation focuses on their ability to capture trends, climatological means, and variability, while ensuring the models do not produce unrealistic or physically implausible results. Using both qualitative and quantitative methods, we address the challenges of model sub-selection within the context of Switzerland's complex terrain.

We evaluate model performance using observational datasets, including high-resolution gridded climatologies and in situ measurements. Statistical metrics such as bias, root mean square error (RMSE), and correlation coefficients are used to assess the agreement between model outputs and observations. Additionally, we evaluate projected future changes by examining their consistency with established physical principles and observed climate trends.

Our analysis demonstrates that the selected subset of models captures a large fraction of the uncertainty in projections from the full ensemble while aligning more closely with observed trends. Furthermore, using a transient time-resampling approach, we show that this subset provides robust information on climate change at different Global Warming Levels. This method can be readily applied to other regions and helps mitigate biases in warming projections caused by time-invariant aerosol forcing.