GLOBAL WARMING - GREENHOUSE GASES VERSUS AEROSOLS

Man's activities have led to an increase in the atmospheric concentration of aerosols and the aerosol precursors as well as to an increase of greenhouse gases. A crude measure of man's global activities, which cause these increases, is the annual emission of carbon-in the form of CO2 from the burning of fossil fuels. Hence as a first approximation, the additional releases of greenhouse gases and the additional production of aerosols are assumed to be proportional to the annual carbon emissions. A simple OD-model provides an estimate of the responses of the global annual average surface temperature to the increase of greenhouse gases and of aerosols. The albedo increase is estimated under the assumption that the additional aerosol production leads to a proportional increase in available cloud condensation nuclei and that the increase of greenhouse gases leads to a proportional decrease in the infrared transmittance of the atmosphere. Both effects are of the same magnitude but of opposite sign; hence, climate modelling requires the full inclusion of aerosols.