ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-7737-2009 Extensive reduction of surface UV radiation since 1750 in world's populated regions Kvalevåg M. M. 1 Myhre G. 1 2 Lund Myhre C. E. 3 Department of Geosciences, University of Oslo, P.B. 1022 Blindern, 0315 Oslo, Norway Center for International Climate and Environmental Research – Oslo (CICERO), P.B. 1129 Blindern, 0318 Oslo, Norway Norwegian Institute for Air Research, P.B. 100, 2027 Kjeller, Norway 19 10 2009 9 20 7737 7751 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/9/7737/2009/acp-9-7737-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/7737/2009/acp-9-7737-2009.pdf

Human activity influences a wide range of components 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 results from a radiative transfer model to surface UV-E radiation for year 2000 derived by satellite observations (from Total 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 investigate the effect of changes in SO<sub>2</sub>, NO<sub>2</sub>, the direct and indirect 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 Hemisphere. Furthermore, our study also shows an extensive surface 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 particularly large in highly populated regions.

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