Temporal Changes in the Radiative Forcing of Aerosol-radiation Interaction (Invited Presentation)

Using observations and multi-model simulations the changes in aerosol distribution over the last decades and its radiative forcing will be described. The model results will be from the historical experiment within Aerosol Comparisons between Observations and Models (AeroCom) with an emphasis on the understanding of the regional changes. Multi-model simulations have earlier been shown to reproduce large regional changes in observed surface sulphate concentrations and here we will show results for a larger set of aerosol chemical and physical properties. The radiative forcing of aerosol-radiation interaction will be divided into contributions from the clear and cloudy sky regions and their significance for the total all sky will be discussed. Further, results of absorbing organic aerosols on the importance for forcing of the aerosol-radiation interaction will be shown. The uncertainties associated with rapid adjustments of black carbon have been large. The discussions have mostly been on rapid adjustments of clouds (semi-direct effects), but here results for other important rapid adjustments terms will be presented. A final comment will be given on outstanding issues for a further constrained quantification of the radiative forcing of aerosol-radiation interaction.