Greenhouse gases (GHZ)

Atmospheric absorption and scattering at different wavelengths of electromagnetic waves. The largest absorption band of carbon dioxide is in the infrared. Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth. In order, the most abundant greenhouse gases in Earth’s atmosphere are:

  • Water vapor (H2O)
  • Carbon dioxide (CO2)
  • Methane (CH4)
  • Nitrous oxide (N2O)
  • Ozone (O3)
  • Chlorofluorocarbons (CFCs)

Atmospheric concentrations of greenhouse gases are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound).The proportion of an emission remaining in the atmosphere after a specified time is the “airborne fraction” (AF). More precisely, the annual airborne fraction is the ratio of the atmospheric increase in a given year to that year’s total emissions. Over the last 50 years (1956–2006) the airborne fraction for CO2 has been increasing at 0.25 ± 0.21%/year.