Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 8 2009 10.5194/acp-9-2863-2009 http://www.atmos-chem-phys.net/9/2863/2009/ http://www.atmos-chem-phys.net/9/2863/2009/acp-9-2863-2009.html http://www.atmos-chem-phys.net/9/2863/2009/acp-9-2863-2009.pdf 2863 2871 2009-04-30 The contribution of anthropogenic bromine emissions to past stratospheric ozone trends: a modelling study B.-M. Sinnhuber bms@iup.physik.uni-bremen.de N. Sheode M. Sinnhuber M. P. Chipperfield W. Feng Institute of Environmental Physics, University of Bremen, Bremen, Germany School of Earth and Environment, University of Leeds, Leeds, UK Bromine compounds play an important role in the depletion of stratospheric ozone. We have calculated the changes in stratospheric ozone in response to changes in the halogen loading over the past decades, using a two-dimensional (latitude/height) model constrained by source gas mixing ratios at the surface. Model calculations of the decrease of total column ozone since 1980 agree reasonably well with observed ozone trends, in particular when the contribution from very short-lived bromine compounds is included. Model calculations with bromine source gas mixing ratios fixed at 1959 levels, corresponding approximately to a situation with no anthropogenic bromine emissions, show an ozone column reduction between 1980 and 2005 at Northern Hemisphere mid-latitudes of only ≈55% compared to a model run including all halogen source gases. In this sense anthropogenic bromine emissions are responsible for ≈45% of the model estimated column ozone loss at Northern Hemisphere mid-latitudes. However, since a large fraction of the bromine induced ozone loss is due to the combined BrO/ClO catalytic cycle, the effect of bromine would have been smaller in the absence of anthropogenic chlorine emissions. 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