A global study of the direct radiative forcing due to the combination of all important anthropogenic and natural aerosol constituents in the atmosphere was performed. Concentrations were constrained by observations to the greatest extent possible. In the presence of clouds, predicted solar plus infrared direct forcings due to anthropogenic aerosols, stratospheric aerosols, all aerosols, and greenhouse gases were -0.113, -0.192, -1.63, and +1.41 W m-2, respectively, implying an anthropogenic greenhouse gas to anthropogenic aerosol forcing ratio of about 7:-1 and a total to anthropogenic aerosol forcing ratio of 8:1. Clouds caused a forcing of -21.6 W m-2, comparable with observations. rcings due to anthropogenic sulfate, elemental carbon, soil aerosols, and sea spray aerosols were -0.415, +0.397, -0.201, and -0.766 W m-2, respectively. Chloride and associated hydrated water in sea spray were found to be the most important aerosol constituents in the atmosphere in terms of direct forcing. Clouds reduced the magnitude of forcing of all aerosol constituents
Symposium on Interdisciplinary Issues in Atmospheric Chemistry