Greenhouse gas

Greenhouse gases are gases in an atmosphere that absorb and emit infrared radiation. By doing so they produce the greenhouse effect.

On Earth, the wavelength bands of interest are centered around 10 microns with most of the radiant energy contained within the range of about 5 to 30 microns. The main greenhouse gases for Earth are water vapor (H₂O), carbon dioxide (CO₂), and ozone (O₃). Some other gases such as methane, chlorofluorocarbons and nitrous oxide play small but not negligible parts in the greenhouse effect.

Plans to reduce the human contribution to the Earth's greenhouse effect concentrate chiefly on carbon dioxide emissions. See Kyoto Protocol, emissions trading and carbon credits.