Tropospheric ozone and its precursors: reanalysis over the past 45 years and projections for 2030

Within the EU project RETRO a reconstruction is made of the chemical composition of the troposphere since 1960 with focus on ozone and its precursors. Long-term simulations are currently being performed using several global chemistry-transport and chemistry-climate models. Meteorological input is provided by the 45-year reanalysis ERA-40, which has recently been completed by the European Centre for Medium-Range Weather Forecasts (ECMWF). Changes in anthropogenic emissions are taken into account by a new inventory covering the whole period; estimates of the interannual variability of biomass burning and biogenic emissions are also included in the models. In this paper we present some preliminary results of this chemical reanalysis, which eventually should include changes in tropospheric ozone and precursor gases as well as in the associated radiative forcing. The results of the reconstruction will also be discussed in the context of the future changes to be expected on the basis of the 2030 Photcomp experiment, which has recently been performed as a contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). In this experiment projections are made of the air quality and the tropospheric composition for the year 2030 based on the new International Institute for Applied Systems Analysis (IIASA) emission scenarios Current Legislation and Maximum Technically Feasible Reduction as well as the IPCC Special Report on Emission Scenarios (SRES) scenario A2.