From continental to street scales: climate change impacts on atmospheric composition over Europe and London

Climate change will impact ozone (O3) and fine particulate matter (PM2.5) through its influence on natural emissions, atmospheric chemistry, deposition and transport. A coupled modelling approach is employed to identify the key processes and determine how regional air pollution across Europe and urban-scale air quality in London in the 2090s are impacted by climate change under Representative Concentration Pathway (RCP) 8.5. Climate change projections from the HadGEM2-ES Earth System Model nudge the nested WRF-EMEP4UK model, which drives the street-scale ADMS-Urban model. Annual-mean temperature increases exceeding 4 °C produce substantial increases in summer biogenic isoprene emissions. There is a strong contrast in the summer and winter-mean O3 responses to climate change, with large summer increases over southern Europe (up to 10 ppbv) and winter decreases over Europe. Annual-average PM2.5 concentrations are elevated (5–10 µg m−3) over most of Europe, also driven by higher summer isoprene emissions that promote secondary organic aerosol formation. Decreases in primary and inorganic PM2.5 components are prominent in winter. The seasonality of urban air pollution is modified over London under climate change: the O3 peak amplitude is reduced, whilst the winter peaks in PM2.5 and NO2 are more pronounced, with nighttime increases. The diurnal profile of urban air pollution typically flattens. Climate induced changes in O3 aid attainment of long-term air quality guidelines in northern Europe, but pose challenges elsewhere. Achieving long-term PM2.5 guidelines over much of Europe becomes increasing difficult with climate change, while attaining short-term air quality guidelines in London remains a major challenge, especially for NO2.