Work

Using regional warming levels to describe future climate change for services and adaptation: Application to the French reference trajectory for adaptation

Year: 2025

Type: article

Abstract: To describe regional climate change, climate services typically rely on an ensemble of climate model simulations. The development and arrival of observational constraints at regional scales are questioning this approach, as some simulations may not align with warming trajectories estimated by these techniques. This study proposes a methodology for describing future regional changes that combines multiple sources of information: global and regional observational constraints applied to the CMIP6 ensemble, along with existing regional climate model simulations driven by CMIP5. This approach uses Regional Warming Levels (RWLs), mirroring the use of Global Warming Levels (GWLs) in the IPCC AR6. We apply it to mainland France, a region with discrepancies in warming projections between global models, regional models, and observational constraints. Results show that the standard GWL approach produces unrealistically low warming estimates due to overly low regional-to-global warming ratios in some models. Using RWLs allows separation of the annual mean warming estimation (based on observational constraints) from the detailed climate change characteristics (based on regional models). We explore ways to link RWLs and GWLs and assess associated uncertainties. This methodology has been selected to describe future climate change in mainland France, as part of the definition of a reference trajectory for adaptation set by the French government. It can be replicated in other regions and applied to existing or upcoming climate projections to express them in terms of regional warming levels at the national scale.

Source: Climate Services

DOI: 10.1016/j.cliser.2025.100553

Authors: Lola Corre, Aurélien Ribes, Sébastien Bernus, Agathe Drouin, Samuel Morin, Jean-Michel Soubeyroux

Institutions: Centre National de la Recherche Scientifique, Centre National de Recherches Météorologiques, Météo-France, Université de Toulouse

Language: English

Topic: Climate variability and models

Subfield: Global and Planetary Change

Field: Environmental Science

Domain: Physical Sciences

SDG: Climate action

Open Access status: gold

Estimated APC paid: $2,290