An assessment of the impact of pollution on global cloud albedo

Increased pollution leads to increasing particulate concentrations. Since some particles nucleate drop formation, clouds will contain, with increasing pollution, more drops per unit volume, and hence will tend to be optically thicker and more reflecting. An opposite effect is also present, in that increasing absorption also attends increasing pollution. Measurements suggest that the former (brightening) effect is the dominant one for global climate and that the climatic effect is quite comparable to that of increased carbon dioxide, and acts in the opposite direction.