European atmosphere in 2050, a regional air quality and climate perspective under CMIP5 scenarios

Abstract : To quantify changes in air pollution in Europe at the 2050 horizon, we designed a comprehensive modelling system that captures external factors such as climate change and long range transport and relies on up-to-date and consistent sets of air pollution and climate policy scenarios. An economical analysis of the costs associated to the selected emission scenarios is performed as well as a monetisation of the health impact of air pollution, so that the suite of full-frame regional climate and chemistry models is at the centre of a comprehensive cost-benefit analysis. Global and regional climate as well as global chemistry simulations are based on the recent Representative Concentrations Pathways (RCP) produced for the Fifth Assessment Report (AR5) of IPCC whereas regional air quality modelling is based on the updated emissions scenarios produced in the framework of the Global Energy Assessment. We explored two diverse scenarios: a reference scenario where climate policies are absent and a mitigation scenario which limits global temperature rise to within 2°C by the end of this century. This first assessment of projected air quality and climate at the regional scale based on CMIP5 (5th Climate Model Intercomparison Project) climate simulations is in line with the existing literature using CMIP3. Sensitivity simulations show that the main factor driving future air quality projections is air pollutant emissions, rather than climate change or long range transport. Whereas the well documented 'climate penalty' bearing upon ozone over Europe is confirmed, other features appear less robust compared to the literature: such as the impact of climate on PM2.5. The cost-benefit analysis allows putting in perspective the economical cost of climate mitigation with the expected co-benefits in terms of air pollutant reduction in Europe.