The impact of greenhouse gases and halogenated species on future solar UV radiation doses

The future development of stratospheric ozone layer depends on the concentration of chlorine and bromine containing species. The stratosphere is also expected to be affected by future enhanced concentrations of greenhouse gases. These result in a cooling of the winter polar stratosphere and to more stable polar vortices which leads to enhanced chemical depletion and reduced transport of ozone into high latitudes. One of the driving forces behind the interest in stratospheric ozone is the impact of ozone on solar UV-B radiation. In this study UV scenarios have been constructed based on ozone predictions from the chemistry-climate model runs carried out by GISS, UKMO and DLR. Since cloudiness, albedo and terrain height are also important factors, climatological values of these quantities are taken into account in the UV calculations. Relative to 1979-92 conditions, for the 2010-2020 time period the GISS model results indicate a springtime enhancement of erythemal UV doses of up to 90% in the 60-90 degrees N region and an enhancement of 100% in the 60-90 degrees S region. The corresponding maximum increases in the annual Northern Hemispheric UV doses are estimated to be 14 % in 2010-20, and 2 % in 2040-50. In the Southern Hemisphere 40 % enhancement is expected during 2010-20 and 27 % duping 2040-50.