Nitrous Oxide and Climate Change

Nitrous oxide, or N2O, is the third most important of the greenhouse gases in global warming terms, after carbon dioxide and methane. This is because, although it only comprises 320 parts per billion of Earth's atmosphere, it has a global warming potential nearly 300 times that of carbon dioxide. The largest source is agriculture, driven mainly by the use of synthetic nitrogen fertilizers. The other major diffuse source derives from release of NOx into the atmosphere from fossil fuel combustion and biomass burning, as well as ammonia from livestock manure. Some N2O also comes directly from combustion, and from two processes in the chemical industry: the production of nitric acid, and the production of adipic acid (used in nylon manufacture).

Keith Smith is an Honorary Professor in the School of Geosciences at the University of Edinburgh, and now lives in Devon, southwest England.