Climate change is likely to significantly affect future air quality over Europe. According to a recent European study, climate change alone is likely to significantly increase ozone pollution in Europe and by as much as 50 ug.m-3 (micrograms per cubic metre) over central France in July by the year 2100, compared with 1990 levels.
Although emissions from human activities are a major cause of climate change, climate change is, in turn, affecting the concentration and spread of pollutant emissions in the atmosphere resulting in a feedback loop between climate and chemistry in the atmosphere.
Partly conducted under the EU projects ACCENT1 and COST728 2, this study investigated the impact of climate change on two major pollutants affecting air quality, ground-level ozone and particulate matter (PM), over Europe.
In addition to being a greenhouse gas (GHG) that contributes to climate change, ozone is a potent secondary pollutant formed from other pollutants (precursor emissions) in the presence of sunlight, which negatively affects human health and the ecosystems. Global ozone levels have increased by 35 per cent since pre-industrial times, primarily due to increases in emissions of nitrogen oxides which are precursors to the formation of ozone.
Particulate matter, i.e. PM10 and PM2.5, are of concern because they have harmful impacts on human health, especially people with lung conditions. Increasing levels of direct emissions of PM and secondary formation of PM in the atmosphere are contributing to high levels of PM in Europe.
Using combined chemistry-transport and global atmospheric circulation models, the study simulated the impact of climate change on air quality at the regional level in the year 2100 (compared with a reference year of 1990). A worst-case climate scenario was assumed (IPPC A2 scenario), where human-induced air pollution emissions remained at the same levels as in the year 2003. This method revealed changes in air quality solely caused by climate change.
Modelling results suggest monthly average levels of ozone could reach around 110ug.m-3 (micrograms per cubic metre) over central France in July 2100, an increase of 50ug.m-3 from the year 1990. Large areas of south-western Europe will experience average ozone levels of around 110-125ug.m-3 in July 2100, up from 95-105ug.m-3 in July 1990. Projected increases (and decreases) in PM levels depended on the region and month. The highest levels are likely to occur over land in October, while over water, the concentration of PM will decrease.
Factors that could explain these changes could be an increase in relative humidity, and changes in the atmospheric mixing layer height in 2100 climate, compared with the reference year of 1990. These changes could lead to stagnant conditions in which high concentrations of PM build up near the surface of the Earth.
The approach of this study, which incorporates local and regional conditions, is essential if climate change impacts on air quality are to be managed in order to meet European air quality standards.