European summer surface ozone 1990–2100

Abstract. The impact of climate change and changes in ozone precursor emission on summer surface ozone in Europe was studied using a regional CTM over the period 1990 to 2100. Two different climate simulations under the SRES A1B scenario together with ozone precursor emission changes from the RCP4.5 scenario were used as model input. In southern Europe regional climate change leads to increasing surface ozone concentrations during April–September, but projected emission reductions in Europe have a stronger effect, resulting in net reductions of surface ozone concentrations. In northern Europe regional climate change decreases surface O₃ and reduced European emissions acts to further strengthen this trend also when including increasing hemispheric background concentrations. The European O₃ precursor emission reductions in RCP4.5 are substantial and it remains to be seen if these reductions can be achieved. There is substantial decadal variability in the simulations forced by climate variability which is important to consider when looking at changes in surface O₃ concentrations, especially until the first half of the 21st century. In order to account for changes in background O₃ future regional model studies should couple global (hemispheric) and regional CTMs forced by a consistent set of meteorological and precursor emission data.