Nitrous oxide (N2O) is a colourless, non-flammable gas with a sweetish odour, commonly known as "laughing gas", and sometimes used as an anaesthetic. Nitrous oxide is naturally produced by oceans and rainforests. Man-made sources of nitrous oxide include nylon and nitric acid production, the use of fertilisers in agriculture, cars with catalytic converters and the burning of organic matter. Nitrous oxide is broken down in the atmosphere by chemical reactions that involve sunlight.
Like carbon dioxide and methane, nitrous oxide is a greenhouse gas whose molecules absorb heat trying to escape to space. Nitrous oxide contributes to the Earth's natural greenhouse effect. Man-made emissions of nitrous oxide are helping to enhance the greenhouse effect. Since the beginning of the Industrial Revolution, atmospheric nitrous oxide concentration has increased by about 16%, and has contributed 4 to 6% to the enhancement of the greenhouse effect.