Impacts of regional climate change on air quality projections and associated uncertainties

A 2-degree global warming is likely to affect the production, deposition, and transport of air pollutants, leading to impacts on air quality and health. In the present study we use an ensemble of four regional chemistry-transport models, driven by meteorological data from different climate models, to assess such changes and their uncertainties for PM2.5 and SOMO35. Changes and uncertainties are compared to the inter-model variability. We find that the impact of regional climate change on PM2.5, averaged over the model ensemble, ranges from -0.5 mu g.m(-3) to +1.3 mu g.m(-3) over Europe. It mainly results from changes in natural and biogenic emissions, such as desert dust, sea salt and biogenic VOCs. Statistically significant decreases in PM2.5 are found over southwestern Russia and Ukraine as well as an increase over Southern Spain. Modeled changes in summer ozone levels range from -1.7 to 1.6 ppbv. We find a smaller ensemble-mean evolution of SOMO35 as compared to inter-model variability. We also investigate the uncertainty due to inter-decadal variability and find that 10-year periods may not be sufficient to allow the detection of statistically significant change signals.