Douville (2026) Faster than expected drying in western Europe: mechanisms, attribution and implications

Identification

• Journal: Climate Dynamics
• Year: 2026
• Date: 2026-01-20
• Authors: Hervé Douville
• DOI: 10.1007/s00382-025-08013-y

Research Groups

Météo-France, CNRS, Univ. Toulouse, CNRM, Toulouse, France

Short Summary

This study investigates the faster-than-expected drying trend in western Europe (1979–2022) compared to climate model projections, attributing the mismatch primarily to systematic errors in the simulated radiative forcing by sulfate aerosols. Using a Bayesian statistical method, the research constrains CMIP6 projections, revealing a more rapid future drying over the region than previously unconstrained models suggest.

Objective

• To better understand the mechanisms driving the recent drying trend over western Europe and reduce the mismatch between climate models and observations, specifically by investigating the roles of atmospheric circulation and anthropogenic aerosols.

Study Configuration

• Spatial Scale: Western Europe (10° W–30° E / 35° N–60° N), Northern Hemisphere extratropics, global.
• Temporal Scale: Recent decades (1979–2022) for observations and atmosphere-only simulations; 1850–2100 for CMIP coupled model projections; focus on spring to summer (April to September, AMJJAS) season.

Methodology and Data

• Models used:
  • ARPEGE-Climat v6 AGCM (Atmospheric General Circulation Model) in three configurations: standard AMIP, nudged (ANUV), and nudged with climatological aerosols (BNUV).
  • Coupled Model Intercomparison Project Phase 5 (CMIP5) models (31 models).
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) models (38 models).
• Data sources:
  • ERA5 atmospheric reanalysis (precipitation, wind fields, sea level pressure).
  • REGEN precipitation dataset (independent in situ precipitation data).
  • HadCRUT5 (global mean surface temperature).
  • MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, version 2) for radiative fluxes.
• Methods:
  • Standardized Precipitation Index (SPI) calculation (SPI3, SPI6, SPI12).
  • Wind nudging technique to constrain AGCM atmospheric circulation towards ERA5.
  • Linear regression for trend analysis.
  • Bayesian statistical method: Kriging for Climate Change (KCC) toolbox to constrain CMIP6 projections with observational data.

Main Results

• Observed drying over western Europe (1979–2022) is faster than simulated by CMIP5 and CMIP6 models, which show a delayed drying response.
• The ARPEGE-Climat AGCM, when nudged towards ERA5 winds, successfully captures the observed multi-decadal trends in sea level pressure (SLP) and SPI6 over western Europe, highlighting the key role of large-scale atmospheric circulation.
• The mismatch between models and observations is unlikely due to internal climate variability but is strongly linked to a delayed reversal of the forced precipitation response in models.
• CMIP6 models simulate a too strong "brightening effect" (increase in surface downward solar radiation and evapotranspiration) from 1979 to 2022, leading to an underestimated drying trend.
• The KCC method, constrained by HadCRUT5 and MERRA-2 data, indicates that the effective radiative forcing (ERF) by sulfate aerosols has been overestimated in CMIP5 and CMIP6 models, resulting in a weaker dimming and brightening effect than observed.
• Constrained CMIP6 projections, using KCC, show a faster future drying and a more rapid increase in the percentage area under moderate drought over western Europe compared to unconstrained projections.

Contributions

• Provides robust evidence that the observed faster-than-expected drying in western Europe is a real phenomenon not adequately captured by current CMIP5 and CMIP6 models.
• Identifies the overestimation of anthropogenic sulfate aerosol radiative forcing in climate models as a primary cause for the discrepancy between simulated and observed recent drying trends.
• Demonstrates the critical importance of accurately representing aerosol forcing pathways for reliable regional climate projections, especially for the water cycle.
• Offers a benchmark for evaluating climate models' ability to simulate multi-decadal precipitation evolution in response to anthropogenic aerosol forcing.
• Highlights the value of observational constraints (e.g., KCC method) for narrowing uncertainty in regional climate change projections, particularly for adaptation strategies.

Funding

Not explicitly stated in the provided text.

Citation

@article{Douville2026Faster,
  author = {Douville, Hervé},
  title = {Faster than expected drying in western Europe: mechanisms, attribution and implications},
  journal = {Climate Dynamics},
  year = {2026},
  doi = {10.1007/s00382-025-08013-y},
  url = {https://doi.org/10.1007/s00382-025-08013-y}
}