Contribution of large-scale atmospheric circulation and anthropogenic aerosols to recent summer warming over western Europe
Douville, Hervé ; Roehrig, Romain ; Nabat, Pierre
Global climate models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) have been shown to underestimate the observed recent warming over western Europe despite their overestimated global warming. Several hypotheses have been proposed to explain this paradox, including the role of anthropogenic aerosols and of large-scale atmospheric circulation. Here, three sets of global atmospheric simulations driven by prescribed radiative forcings and oceanic boundary conditions are used to better understand the observed recent warming over western Europe. In the control experiment, the model underestimates the observed warming despite the use of observed sea surface temperatures (SST). A spectral nugding of the dynamics towards ERA5 reanalysis allows the model to capture accurately both the high-frequency variability and multi-decal trends of the observed near-surface temperature. The use of climatological rather than slowly evolving anthropogenic aerosols suggests a minor radiative contribution to the recent warming. Overall, the results suggest that changes in large-scale atmospheric circulation and regional feedbacks are not mutually exclusive explanations for the amplified summer warming over western Europe. The forced component of the observed circulation changes and the implications for the CMIP6 projections are also briefly discussed.</p>
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