Aerosols are airborne particles or a collection of such particles. Some of them are of natural origin, like sea salt particles while others are of anthropogenic origin like dust or smoke. It was pointed out in recent years that aerosols play an important role in climate forcing in two ways. First, the scattering and the absorption of the incoming solar radiation by aerosols has a direct influence on the radiative budget of the Earth’s atmosphere. Second, an indirect effect is the enhancement of cloud formation [Houghton et al.;2001]. The presence of aerosols increases the cloud condensation nuclei concentration and consequently increases the absorption of UV-B radiation.