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Nitrous oxide (N2O) is the third most important long-lived greenhouse gas, after carbon dioxide (CO2) and methane. Nitrous oxide is also one of the main stratospheric ozone depleting substances and we are releasing more of it into the atmosphere than previously thought. Dinitrogen oxide occurs naturally and also as a result of man’s activities. In environmental conditions it is a colourless, sweet smelling gas.
Impact of Nitrous Oxide on Climate Change
- The anaesthetic and analgesic properties of nitrous oxide have been used in medicine and dentistry since the late nineteenth century, when it was also used as a recreational drug.
- Now, it is used in the dairy industry as a mixing and foaming agent, in motor sports to speed engines and by deep sea divers to avoid nitrogen narcosis. Increasing use of nitrogen fertilizers is leading to higher N2O levels in the atmosphere.
- Nitrous oxide is released naturally from soils and water bodies as part of the microbial processes of nitrification and denitrification. The two major man-made sources are from agriculture (application of fertilisers to soils and subsequent leaching to water bodies) and the manufacture of acids and nylon. It is also released from power stations and road transport (particularly since the introduction of catalytic convertors).
- Although relatively small amounts are released, it has a high “global warming potential” (310 times that of carbon dioxide). Like other greenhouse gases, nitrous oxide absorbs radiation and traps heat in the atmosphere, where it can live for an average of 114 years.
- While in the stratosphere, nitrous oxide is exposed to sunlight and oxygen which converts the gas into nitrogen oxides. Nitrogen oxides can damage the ozone layer, thus reducing the protection offered from harmful UV sun rays.
- Depletion of the stratospheric ozone layer (in which nitrous oxide plays a part) means that humans may be exposed to high doses of UV sunlight which might cause skin cancers.
- At normal environmental concentrations, nitrous oxide is not harmful to humans. Inhalation of higher concentrations in an enclosed space could however exclude oxygen, causing dizziness, nausea and eventually unconsciousness.
- The United Nations Framework Convention on Climate Change (Kyoto Protocol, 1997) introduced measures designed to achieve reduction of greenhouse gas releases (including nitrogen monoxide).
- A 2013 report by the United Nations found that since the pre-industrial era, nitrous oxide emissions from human activities have increased 20%. At the time, the authors wrote that if nothing was done, those emissions were expected to double by 2050.
- Despite nitrous oxide’s role depleting the ozone layer, it is not included in the Montreal Protocol on Substances that Deplete the Ozone Layer, an international treaty that aims to restore the ozone layer by phasing out certain substances.
