Séminaire : Earth's albedo decrease over continental regions with reduced aerosol emissions - Noé Clément

Earth’s top-of-atmosphere albedo has been declining for more than 3 decades, with the decline steepening since the 2010s. Because outgoing longwave radiation is not increasing fast enough to compensate, this leads to a growing Earth Energy Imbalance. Three regions – Europe, Eastern North America, and East Asia – exhibit trends in top-of-atmosphere albedo 2 to 4 times larger than the global trend, the three of them together accounting for 15% of this global trend. These are also regions exhibiting strong decreases in aerosol emissions since the 2000s, due to air quality policies. Using both satellite retrievals from CERES and MODIS instruments and CMIP6 simulations from 8 climate models, we investigate these regional trends in top-of-atmosphere albedo over the 2003–2025 period and disentangle their causes, either from aerosol-related changes or climate feedbacks. We build a 2D framework in which changes in aerosol optical depth, cloud cover, liquid and ice water paths, droplet number, surface albedo, and surface temperature are used to estimate changes in top-of-atmosphere albedo. Satellite retrievals suggest that half of the combined trend over these three regions could be attributed to decreasing aerosol emissions, corresponding to 7% of Earth’s albedo decrease. This proportion is higher in most CMIP6 models, which overestimate aerosol contributions, underestimate climate feedback contributions, and simulate lower global albedo trends. Climate model sensitivities could therefore have been underestimated. Intervenant : Noé Clément (IPSL) Pour en savoir plus Clément N., N. Bellouin, O. Boucher, J. Quaas, H. Jia, I. Tegen, 2026 : Aerosol and non-aerosol drivers of regional trends in top-of-atmosphere albedo over 2002–2020 https://iopscience.iop.org/article/10.1088/1748-9326/ae687e