Since the 1980s anthropogenic aerosols have been considerably reduced in Europe and the Mediterranean area. This decrease is often considered as the likely cause of the brightening effect observed over the same period. This phenomenon is however hardly reproduced by global and regional climate models. Here we use an original approach based on reanalysis-driven coupled regional climate system modeling to show that aerosol changes explain 81±16% of the brightening and 23±5% of the surface warming simulated for the period 1980-2012 over Europe. The direct aerosol effect is found to dominate in the magnitude of the simulated brightening. The comparison between regional simulations and homogenized ground-based observations reveals that observed surface solar radiation and land and sea surface temperature spatiotemporal variations over the Euro-Mediterranean region are only reproduced when simulations include the realistic aerosol variations. Key Points A regional climate system model over the Euro-Mediterranean includes aerosols Aerosol changes are needed to reproduce observed climate trends since 1980 Aerosols play an essential role in the brightening and warming since 1980

This work is a contribution to the HyMeX (HYdrological cycle in the Mediterranean EXperiment) and ChArMEx (Chemistry-Aerosol Mediterranean Experiment) program through INSU-MISTRALS support and the Med-CORDEX initiative (COordinated Regional climate Downscaling EXperiment Mediterranean region, www.medcordex.eu). This research has been supported by the French National Research Agency (ANR) project REMEMBER (contract ANR-12-SENV-001). Gridded temperature data sets, GISS and CRUTEM, have been provided, respectively, by the NASA Goddard Institute for Space Studies and the Met Office Hadley Center. HISTALP temperature data sets have been downloaded from http://www.zamg.ac.at/histalp. We also thank Brigitte Dubuisson and Anne-Laure Gibelin for the availability of homogenized temperature series in France, and we acknowledge the data providers in the ECA&D project. A. S. L. was supported by the "Secretaria per a Universitats i Recerca del Departament d'Economia i Coneixement, de la Generalitat de Catalunya i del programa Cofund de les Accions Marie Curie del 7e Programa marc d'R+D de la Unio Europea" (2011 BP-B 00078), the postdoctoral fellowship JCI-2012-12508, and the project NUCLIERSOL (CGL2010-18546)