Abstract

Earth's climate is warming as a result of anthropogenic emissions of greenhouse gases, particularly carbon dioxide (CO2) from fossil fuel combustion. Anthropogenic emissions of non-CO2 greenhouse gases, such as methane, nitrous oxide and ozone-depleting substances (largely fromsources other than fossil fuels), also contribute significantly to warming. Some non-CO2 greenhouse gases have much shorter lifetimes than CO2, so reducing their emissions offers an additional opportunity to lessen future climate change. Although it is clear that sustainably reducing the warming influence of greenhouse gases will be possible only with substantial cuts in emissions of CO2, reducing non-CO2 greenhouse gas emissions would be a relatively quick way of contributing to this goal.