A warming adjustment method for CORDEX RCM simulations

Abstract. Regional climate model (RCM) projections provide high-resolution information essential for climate impact assessments and adaptation planning. Currently available Coordinated Regional Climate Downscaling Experiment (CORDEX) simulations, driven by CMIP5 global models, exhibit considerably weaker European warming throughout the 21st century compared to the latest Coupled Model Intercomparison Phase 6 (CMIP6) models. This discrepancy arises from multiple factors: RCMs tend to underestimate warming compared to their driving models in part due to the use of aerosol climatologies, while CMIP6 models themselves exhibit higher climate sensitivity than their CMIP5 predecessors. Here, we present a method to adjust existing CORDEX simulations toward the large-scale warming simulated by CMIP6 models while preserving fine-scale spatial structure and physical coherence. The method operates by reassembling complete annual fields from the original simulations according to smoothed temperature trajectories, maintaining temporal monotonicity without requiring interpolation. We demonstrate its application to both temperature and precipitation, including mean conditions and extremes over Europe, though the approach is applicable to any regional domain and warming-sensitive climate variable. As an extension, the method can be applied sequentially to establish consistency from prescribed global warming levels through CMIP6 regional patterns to high-resolution RCM projections. This bridges the temporal gap between regional and global model development cycles, making existing high-resolution climate information compatible with both updated model generations and specific warming targets.