Extensive reduction of surface UV radiation since 1750 in world's populated regions
Human activity influences a wide range of com-ponents that affect the surface UV radiation levels, among them ozone at high latitudes. We calculate the effect of human-induced changes in the surface erythemally weighted ultra-violet radiation (UV-E) since 1750. We compare re-sults from a radiative transfer model to surface UV-E radia-tion for year 2000 derived by satellite observations (from To-tal Ozone Mapping Spectroradiometer) and to ground based measurements at 14 sites. The model correlates well with the observations; the correlation coefficients are 0.97 and 0.98 for satellite and ground based measurements, respectively. In addition to the effect of changes in ozone, we also inves-tigate the effect of changes in SO 2 , NO 2 , the direct and indi-rect effects of aerosols, albedo changes and aviation-induced contrails and cirrus. The results show an increase of surface UV-E in polar regions, most strongly in the Southern Hemi-sphere. Furthermore, our study also shows an extensive sur-face UV-E reduction over most land areas; a reduction up to 20% since 1750 is found in some industrialized regions. This reduction in UV-E over the industrial period is particu-larly large in highly populated regions.