Montreal protocol benefits simulated with CCM SOCOL
Ozone depletion is caused by the anthropogenic increase of halogen containing species in the atmosphere, which results in the enhancement of the concentration of reactive chlorine and bromine in the stratosphere. To reduce the influence of an-thropogenic ozone-depleting substances (ODS), the Montreal Protocol was agreed by 5 Governments in 1987, with several Amendments adopted later. In order to assess the benefits of the Montreal Protocol and its Amendments (MPA) on ozone and UV radia-tion, two different runs of the chemistry-climate model (CCM) SOCOL have been car-ried out. The first run was driven by the emission of ozone depleting substances (ODS) prescribed according to the restrictions of the Montreal Protocol and all its Amend-10 ments. For the second run we allow the ODS to grow by 3 % annually. We find that the MPA would have saved up to 80 % of the global annual total ozone by the end of the 21st century. Our calculations also show substantial changes in surface tempera-ture and precipitations that could occur in the world without MPA implementations. To illustrate the changes in UV radiation at the surface and to emphasize certain features 15 which can only be seen for some particular regions if the influence of the cloud cover changes is accounted for, we calculate geographical distribution of the erythemally weighted irradiance (E ery). For the no Montreal Protocol simulation E ery increases by factor of 4 to 16 between the 1970s and 2100. For the scenario including the Montreal Protocol it is found that UV radiation starts to decrease in 2000, with continuous decline 20 of 5 % to 10 % at middle latitudes in the Northern and Southern hemispheres.