Oxides of Nitrogen

Oxides of nitrogen, chlorofluorocarbons (CFCs), and ozone have a lesser effect on the atmosphere than carbon dioxide and methane, but as you will see they are important contributors to the greenhouse effect. We hope you are getting an understanding of how important all these gases are to the environment and to our global climate.

Oxides of nitrogen include nitric oxide and nitrogen dioxide. Pre-industrial levels were 275 ppb and in 1994 the atmospheric levels were up to 312 ppb, showing an increase in 15 percent. Anthropogenic sources account for about 33 percent of the total production. Molecule per molecule they have about 250 times the heat absorbing capacity of carbon dioxide but their radiative forcing is just 0.14Wm-2. Currently they are increasing at a rate of 0.25 percent per year.

The following are sources of oxides of nitrogen:

• Mainly produced by microbes in the soil in response to agriculture, but also produced in the ocean, from burning of timber, from fertilizers and from combustion of fossil fuels. Oxides of nitrogen also influence ozone.
• Nitrogen dioxide is involved with destruction of stratospheric ozone. nitrogen oxide, an emission from the combustion engine, is involved with production of ozone in the troposphere.

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