The impact of future atmospheric circulation changes over the Euro-Atlantic sector on urban PM_2.5 concentrations

Abstract

Air quality management is strongly driven by legislative aspects related to the exceedance of air quality limit values. Here, 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 PM 2.5 concentrations in Europe. Daily PM 2.5 concentrations are assessed using a novel downscaling method which allows us to compute exceedances of current and planned air quality thresholds. For the latter, we assume that future ambitious emission reductions are likely to be accompanied by stricter air quality thresholds. The changes in PM 2.5 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 North Atlantic Oscillation 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 PM 2.5 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 lg/m 3 on 25 to over 50 days per year, and annual guidelines of 10 mg/m 3 on more than 80% of the 30 years analysed in our study. We 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.

Long-term trends in PM2.5 mass and particle number concentrations in urban air: The impacts of mitigation measures and extreme events due to changing climates

“…Both PM2.5 and PNC had a monotonic downward trend while long-term measurements of temperature, precipitation, and wind speed had no particular trend. Additionally, the increasing intensity and frequency of climate variabilities causing extreme events due to changing climates also influenced PM concentrations (Jeong et al, 2018;Markakis et al, 2016;Messori et al, 2018).…”

Persistent anomalies of the North Atlantic jet stream and associated surface extremes over Europe

“…Both anomalies in the polarfront jet and merged flow episodes can favour a range of surface extremes in Europe, for example in precipitation, temperature, surface wind or particular matter concentrations [e.g. 8,[10][11][12][13][14][15]. A parallel stream of literature has focused on linking planetary waves to surface extremes [e.g.…”

Long‐term evolution of cold air pools over the Madrid basin

“…Climate model simulations have suggested that southern Europe is likely to experience a higher incidence of positive North Atlantic Oscillation states in the future and a large eastward shift of both North Atlantic sea‐level pressure centres of action, combined with more frequent mid‐latitude blocking and a northward shift of the jet stream. All these atmospheric circulation changes would increase the frequency of stagnant air masses over urban centres and the consequent degradation of air quality, increasing the PM 2.5 concentrations beyond the World Health Organization Air Quality Guidelines (Messori et al ., 2018).…”