Impact of improved air quality on the future evolution of climate

Calculations performed with the Hamburg Climate Model suggest that climate change resulting from increasing greenhouse gas emissions would become considerably more pronounced if air quality were dramatically improved in the future. Specifically, the globally averaged surface air temperature and amount of precipitation could increase in less than a decade by 0.8 K and 3%, respectively, if the entire amount of anthropogenic sulfate aerosols were removed from the atmosphere. The geographic patterns of the calculated changes bear resemblance with those found in greenhouse gas and aerosol scenario experiments (annual mean temperature increase of approximately 1 K on most continents, 4 K in the Arctic). This study suggests that possible future changes as well as the general issue of the stability of atmospheric aerosol loads should be considered in strategies aiming to maintain global warming below a prescribed threshold. It also underscores the need to account for associated possible changes in precipitation in such strategies.