Global sensitivity experiments of the radiative forcing due to mineral aerosols

The radiative effects of mineral dust in the atmosphere are uncertain. Further, the human contribution to the mineral aerosol concentration is difficult to quantify. We have performed several global sensitivity experiments to investigate the radiative forcing due to mineral dust. Two global data sets of mineral aerosol distribution are used. Radiative transfer schemes for thermal infrared and solar radiation are used in the calculations. We have investigated the sensitivity of the global radiative forcing to the spatial distribution of the aerosols, including the altitude, the size distribution, and optical parameters. Our strongest emphasis has been on the size distribution of the mineral aerosol, for which we have found a strong sensitivity. A range of -0.7 Wm(-2) to 0.5 Wm(-2) is estimated for the human influence on the global radiative forcing due to mineral aerosols. We find it almost as probable with a positive radiative forcing as with a negative forcing. Even if the global mean radiative forcing is small, there are large contributions of different sign in certain regions.