The French reference trajectory for climate changeadaptation (TRACC)

To ensure consistency in adaptation policies, the French government has adopted a Reference Warming Trajectory for Adaptation (TRACC). This trajectory is based on current international commitments to limit greenhouse gas emissions and translates them into global warming levels (1.5°C, 2°C, and 3°C), associated with three time horizons (2030, 2050, and 2100, respectively). To address the needs of adaptation stakeholders, these global warming levels have been expressed in terms of regional climate change over French territories, including both mainland France and overseas regions. Discrepancies over mainland France between regional climate projections from the CMIP5 generation and recent warming estimates derived from observational constraints motivated the development of a new methodology. This approach relies on regional warming levels to characterize future climate change consistently with the reference warming trajectory. This presentation outlines the principles of this methodology and its extension to overseas territories. It also describes how this method has been applied to describe future climate change in terms of averages, variability, extremes, and sectoral indicators. Perspectives for updating the description of the reference warming trajectory, based on the downscaling of CMIP6 simulations, are also discussed. They rely on the synthesis of a wide range of diverse and recently developed data sources, including kilometer-scale regional climate models, coupled regional climate models, AI-based emulators, very high-resolution global climate models, and observational constraints.