Temperature and radiative responses to anthropogenic aerosols over the Mediterranean Basin based on CMIP6 Earth system models

Abstract. Here, we assess the amplification of near-surface warming in the Mediterranean (MED) resulting from global anthropogenic aerosol (AA) reductions, based on simulations from CMIP6 Earth system models (ESMs). Temperature and radiative responses are investigated over the MED. The effective radiative forcing (ERF) and near-surface temperature (TAS) exhibit decreasing trends until around 1980 followed by increasing trends, driven by air pollution control policies. The annual mean ERF at the top-of-atmosphere over the MED changes by 2.37±1.06 W m^-2 between the peak AA period (1970–1979) and the near-present period (2005–2014). During this interval, the annual mean TAS increases by 0.67±0.37 °C. Overall, the multi-model ensemble shows a robust amplification of warming over the MED on annual scale resulting from global AA reductions from 1970–1979 to 2005–2014, in good agreement with observational datasets over land. The model simulations indicate that AAs are responsible for 49 % (39 %) of the annual (summer) warming between the two periods. In the winter, ESMs produce an overestimated warming of 1.19 °C, with AAs contributing 60 % to this warming. Finally, we show that circulation changes caused by AA reductions can play an additional role in the redistribution of regional temperature changes apart from the radiative effects per se. Our results reveal a strong link between the recent acceleration of MED warming and global AA decreases, which unmask additional greenhouse gas-driven warming. This study highlights the sensitivity of the MED to global emission changes and the need for climate policies that couple air quality improvements with rapid greenhouse gas mitigation.