Main Greenhouse Gases

Learn more about climate science in our Basics section

The tables below present characteristics of major greenhouse gases. The Global Warming Potential (GWP) indicates the warming effect of a greenhouse gas, while the atmospheric lifetime expresses the total effect of a specific greenhouse gas after taking into account global sink availability. The lifetime indicates how long the gas remains in the atmosphere and increased radiative forcing quantifies the contribution to additional heating over an area. The vast majority of emissions  are carbon dioxide followed by methane and nitrous oxide. Lesser amounts of CFC-12, HCFC-22, Perflouroethane and Sulfur Hexaflouride are also emitted and their contribution to global warming is magnified by their high GWP, although their total contribution is still small compared to the other gases.



Chemical Formula

 Anthropogenic Sources

Atmospheric Lifetime1(years)

 GWP2 (100 Year Time Horizon)



Fossil-fuel combustion, Land-use conversion, Cement Production





Fossil fuels,
Rice paddies,
Waste dumps





Industrial processes, Combustion



Tropospheric Ozone O3Fossil fuel combustion, Industrial emissions, Chemical solventshours-daysN.A.



Liquid coolants,








Sulfur Hexaflouride


Dielectric fluid




Pre-1750 Tropospheric
(parts per billion)

Current Tropospheric
(parts per billion) 






1,870 / 1,7488



 323 / 3228

Tropospheric Ozone 2534



.534 / .5328



.218 / .19410

Sulfur Hexaflouride


.00712 /.006738, 10

Source of graphical information and notes:
Blasing, T.J. ad K. Smith 2011.  "Recent Greenhouse Gas Concentrations."  In Trends: A Compendium of Data on Global Change.  Carbon Dioxide Information Analysis Cetner, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, TN, USA.


  1. The atmospheric lifetime is used to characterize the decay of an instanenous pulse input to the atmosphere, and can be likened to the time it takes that pulse input to decay to 0.368 (l/e) of its original value. The analogy would be strictly correct if every gas decayed according to a simple exponential curve, which is seldom the case. For example, CH4 is removed from the atmosphere by a single process, oxidation by the hydroxyl radical (OH), but the effect of an increase in atmospheric concentration of CH4 is to reduce the OH concentration, which, in turn, reduces destruction of the additional methane, effectively lengthening its atmospheric lifetime. An opposite kind of feedback may shorten the atmospheric lifetime of N2O (IPCC 2007, Section 2.10.3).
  2. The Global Warming Potential (GWP) provides a simple measure of the radiative effects of emissions of various greenhouse gases, integrated over a specified time horizon, relative to an equal mass of CO2 emissions.
  3. Pre-1750 concentrations of CH4,N2O and current concentrations of O3, are taken from Table 4.1 (a) of the IPCC Intergovernmental Panel on Climate Change), 2001. Following the convention of IPCC (2001), inferred global-scale trace-gas concentrations from prior to 1750 are assumed to be practically uninfluenced by human activities such as increasingly specialized agriculture, land clearing, and combustion of fossil fuels. Preindustrial concentrations of industrially manufactured compounds are given as zero. The short atmospheric lifetime of ozone (hours-days) together with the spatial variability of its sources precludes a globally or vertically homogeneous distribution, so that a fractional unit such as parts per billion would not apply over a range of altitudes or geographical locations. Therefore a different unit is used to integrate the varying concentrations of ozone in the vertical dimension over a unit area, and the results can then be averaged globally. This unit is called a Dobson Unit (D.U.), after G. M. B. Dobson, one of the first investigators of atmospheric ozone. A Dobson unit is the amount of ozone in a column which, unmixed with the rest of the atmosphere, would be 10 micrometers thick at standard temperature and pressure.
  4. Because atmospheric concentrations of most gases tend to vary systematically over the course of a year, figures given represent averages over a 12-month period for all gases except ozone (O3), for which a current global value has been estimated (IPCC, 2001, Table 4.1a).
  5. The value given by IPCC 2001, page 185, is 280 ± 10 ppm. This is supported by measurements of CO2 in old, confined, and reasonably well-dated air. Such air is found in bubbles trapped in annual layers of ice in Antarctica, in sealed brass buttons on old uniforms, airtight bottles of wine of known vintage, etc. Additional support comes from well-dated carbon-isotope signatures, for example, in annual tree rings. Estimates of "pre-industrial" CO2 can also be obtained by first calculating the ratio of the recent atmospheric CO2 increases to recent fossil-fuel use, and using past records of fossil-fuel use to extrapolate past atmospheric CO2 concentrations on an annual basis. Estimates of "pre-industrial" CO2 concentrations obtained in this way are higher than those obtained by more direct measurements; this is believed to be because the effects of widespread land clearing are not accounted for. Ice-core data provide records of earlier concentrations. For concentrations back to about 1775, see A. Neftel et al.
  6. Recent CO2 concentration (388.5 ppm) is the 2010 average taken from globally averaged marine surface data given by the National Oceanic and Atmospheric Administration Earth System Research Laboratory, web site:
  7. Pre-industrial concentrations of CH4 are evident in the "1000-year" ice-core records in CDIAC's Trends Online However, those values need to be multiplied by a scaling factor of 1.0119 to make them compatible with the AGAGE measurements of current methane concentrations, which have already been adjusted to the Tohoku University scale. Ten thousand-year records of CH4, CO2 and N2O, from ice-core data, are also presented graphically in IPCC 2007, (Figure SPM.1).
  8. The first value in a cell represents Mace Head, Ireland, a mid-latitude Northern-Hemisphere site, and the second value represents Cape Grim, Tasmania, a mid-latitude Southern-Hemisphere site. "Current" values given for these gases are annual arithmetic averages based on monthly background concentrations for October 2009 through September 2010. The SF6 values are from the AGAGE gas chromatography - mass spectrometer (gc-ms) Medusa measuring system.
  9. Source: IPCC (2007). The pre-1750 value for N2O is consistent with ice-core records from 10,000 B.C.E. through 1750 C.E. shown graphically in figure SPM.1 on page 3.
  10. For SF6 data from January 2004 onward see For data from 1995 through 2004, see the National Oceanic and Atmospheric Administration (NOAA), Halogenated and other Atmospheric Trace Species (HATS) site at: