An assessment of the impact of climate change on air quality at two UK sites

Possible effects of climate change on air quality are studied for two urban sites in the UK, London and Glasgow. Hourly meteorological data were obtained from climate simulations for two periods representing the current climate and a plausible late 21st century climate. Of the meteorological quantities relevant to air quality, significant changes were found in temperature, specific humidity, wind speed, wind direction, cloud cover, solar radiation, surface sensible heat flux and precipitation. Using these data, dispersion estimates were made for a variety of single sources and some significant changes in environmental impact were found in the future climate. In addition, estimates for future background concentrations of NOx, NO2, ozone and PM10 upwind of London and Glasgow were made using the meteorological data in a statistical model. These showed falls in NOx and increases in ozone for London, while a fall in NO2 was the largest percentage change for Glasgow. Other changes were small. With these background estimates, annual-average concentrations of NOx, NO2, ozone and PM10 were estimated within the two urban areas. For London, results averaged over a number of sites showed a fall in NOx and a rise in ozone, but only small changes in NO2 and PM10. For Glasgow, the changes in all four chemical species were small. Large-scale background ozone values from a global chemical transport model are also presented. These show a decrease in background ozone due to climate change. To assess the net impact of both large scale and local processes will require models which treat all relevant scales.