Nitrous oxide (N2O) is a gas better known at the race track as an oxygen source in highly tuned motors for drag racing and other purposes, or in the operating theatre as an anaesthetic. The most common name for nitrous oxide is "laughing gas", since it produces a state of euphoria in lower concentrations. It was discovered in 1776 by Joseph Priestley adding iron to nitrous peroxide. This gave the world laughing gas, from which it was never to recover. Humphry Davy, who was a surgical assistant at the time, subsequently took a whiff when a wisdom tooth bothered him. The instant relief of his pain gave him ideas about the gas's utility.
Nitrous oxide is a gas that occurs in the atmosphere in minute amounts compared to levels of carbon dioxide and water vapour, and is considered to be one of the more potent greenhouse gases.
Nitrous oxide contributes to the greenhouse effect and is of concern because a molecule of nitrous oxide can produce approximately 310 times the global warming potential of carbon dioxide. Even though the quantity of nitrous oxide is nearly three orders of magnitude less than that of carbon dioxide, its contribution to global warming is comparable to that of carbon dioxide.
N2O is a long-lived inert gas in the troposphere but is removed in the stratosphere by light reactions and oxidation. However, nitrous oxide concentrations have risen rapidly since 1940. The increase of nitrous oxide in the atmosphere in the 1980s was 0.25 % and in the last decade has increased at rates from 0.5 % to 1.2 %.
The greater part of the nitrous oxide in the atmosphere comes from activity of micro-organisms, especially in soil below natural vegetation, with the oceans following as a source. Burning fossil fuels was thought early on to be the major contributor in increased concentration; it is now widely accepted that emission from burning stationary fossil fuel contributes less than 1% of the global supply.
Unknown amounts of nitrous oxide are produced by burning biomass, or by exhaust gases from combustion processes, and during catalytic reduction of nitrous oxide (in catalytic converters in cars).