Atmospheric aerosols physically affect the heat balance of the Earth, both DIRECTLY by reflecting and absorbing incoming solar radiation and INDIRECTLY by influencing the properties and processes of clouds and possibly by changing the atmospheric chemistry associated with greenhouse gases. These climatically important processes are perturbed by aerosols from natural sources such as volcanoes, forest fires, and dust storms, and by aerosols from such human activities as the input of sulfur dioxide gases into the atmosphere during fossil fuel burning.
