The impact of future atmospheric circulation changes over the Euro-Atlantic sector on urban PM2.5 concentrations

ir quality management is strongly driven by legislative aspects related to the exceedance of air quality limit values. Here we assume that future ambitious emission reductions are likely to be accompanied by more stringent air quality thresholds. Specifically, we use the Norwegian Climate Centre's Earth System Model to assess the impact of a future scenario of maximum feasible aerosol emission abatement and increasing greenhouse gases (RCP4.5) on urban PM2.5 concentrations in Europe, taking into account changes in the large-scale circulation patterns. Daily PM2.5 concentrations are assessed using a novel downscaling method which allows to compute exceedances of current and planned air quality thresholds. The changes in PM2.5 concentrations are discussed in the context of the large-scale atmospheric changes observed relative to the present-day climate. Our results show a more positive NAO mean state in the future, combined with a large eastward shift of both North Atlantic sea-level pressure centres of action. This is associated with more frequent mid-latitude blocking and a northward shift of the jet stream. These changes favour higher than expected anthropogenic urban PM2.5 concentrations in southern Europe, while they have the opposite effect on the northern half of the continent. In the future scenario, PM concentrations in substantial parts of Southern Europe are found to exceed the World Health Organisation Air Quality Guideline daily limit of 25 μg/m3 in 25 to over 50 days per year, and annual guidelines of 10 μg/m3 in more than 80% of the 30 years analysed in our study. In agreement with previous studies, we therefore conclude that alterations in atmospheric circulation in the future, induced by stringent maximum feasible air pollution mitigation as well as GHG emissions, will negatively influence the effectiveness of these emission abatements over large parts of Europe. This has important implications for future air quality policies.JRC.D.5-Food Securit