Sulfur emission, CCN, clouds and climate : a review

Cloud droplets form exclusively by the condensation of water vapor on cloud condensation nuclei (CCN). The nature and concentration of CCN may thus considerably influence the number of cloud drops. This, in turn, may influence cloud reflectances either directly or indirectly through additional physical processes. The impact on the planetary albedo might be large and might easily cancel or amplify the CO 2 warming. This paper is an overview of the various aspects of this issue