Science 326, 716–718 (2009)
The warming effects of greenhouse gases are likely to be different than currently anticipated, owing to their interactions with aerosols in the atmosphere. Although aerosols are known to cool the climate, the effect of their interactions with greenhouse gases on climate has been unknown.
Drew Shindell, of the NASA Goddard Institute for Space Studies, and colleagues used a model that couples atmospheric composition with climate to examine the impact of aerosols on the warming potential of different greenhouse gases over a 100-year period. They show that gas-aerosol interactions increase the warming potential of methane by 10 per cent, and when aerosol-cloud interactions are included, methane-induced warming increases by 20-40 per cent. A similar, even more pronounced pattern is seen for emissions of carbon monoxide. In contrast, the cooling effect of nitrogen oxides increases when interactions with sulphate aerosols are taken into account.
Although interactions between air pollutants and ecosystems — not considered in this study — are likely to modify these results, the researchers suggest that atmospheric interactions between aerosols and greenhouse gases should be accounted for when evaluating the climatic impact of emissions.