page_title: Greenhouse gas
section_title: Greenhouse gases
hierarchical_section_title: Greenhouse gas / Gases in Earth's atmosphere / Greenhouse gases
context_page_description: A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect on planets. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C, rather than the present average of 15 °C. The atmospheres of Venus, Mars and Titan also contain greenhouse gases.
  Human activities since the beginning of the Industrial Revolution have produced a 45% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 415 ppm in 2019. The last time the atmospheric concentration of carbon dioxide was this high was over 3 million years ago. This increase has occurred despite the uptake of more than half of the emissions by various natural "sinks" involved in the carbon cycle. The vast majority of anthropogenic carbon dioxide emissions come from combustion of fossil fuels, principally coal, oil, and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture.
context_section_description: Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth. Carbon dioxide (0.04%), nitrous oxide, methane and ozone are trace gases that account for almost one tenth of 1% of Earth's atmosphere and have an appreciable greenhouse effect.
   In order, the most abundant greenhouse gases in Earth's atmosphere are:
  Water vapor (H
  ₂O)
  Carbon dioxide (CO
  ₂)
  Methane (CH
  ₄)
  Nitrous oxide (N
  ₂O)
  Ozone (O
  ₃)
  Chlorofluorocarbons (CFCs)
  Hydrofluorocarbons (includes HCFCs and HFCs)
  Atmospheric concentrations 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 or absorption by bodies of water). The proportion of an emission remaining in the atmosphere after a specified time is the "airborne fraction" (AF). The annual airborne fraction is the ratio of the atmospheric increase in a given year to that year's total emissions. As of 2006 the annual airborne fraction for CO
  2 was about 0.45. The annual airborne fraction increased at a rate of 0.25 ± 0.21% per year over the period 1959–2006.
caption: Atmospheric absorption and scattering at different wavelengths of electromagnetic waves. The largest absorption band of carbon dioxide is not far from the maximum in the thermal emission from ground, and it partly closes the window of transparency of water; hence its major effect.
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