The Big Three (Resource)

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Which greenhouse gases are most prevalent?

The three most prevalent greenhouse gases (GHG) are: Carbon dioxide (CO2), Methane (CH4), and Nitrous Oxide (N2O). On WikiCarbon we call them the Big Three. Quantifying the Big Three on a Carbon dioxide equivalent (CO2e) basis -- using 100-year Global Warming Potential (GWP100) conversion factors -- has them, in the forty (40) year period from 1970 through 2010, accounted for approximately 98% of total human-caused (anthropogenic) GHG emissions, on a GWP-weighted basis, as per estimates from the IPCC.[1] Refer to: Greenhouse gas conversion factors for a simple explanation of conversion factors. For an outline of the various greenhouse gases, including methane (CH4), nitrous oxide (N2O), and other trace gases (including CFCs, HCFCs, HFCs, PFCs, and SF6), the following article, What Are Greenhouse Gases? is useful.[2]

Cumulative Human-caused (Anthropogenic) GHG Emissions by Gas (1970-2018)*^[1]
Greenhouse Gas (GHG) 1970 1980 1990 2000 2010 2018^[3] 2019[4]
CO2 from Fossil Fuel and Industrial Processes (Energy) 55% 58% 59% 62% 65% 68% 64%
CO2 from Forestry and Other Land Use Change (FOLU) 17% 15% 16% 13% 11% 7% 11%
Sub-total CO2 72% 73% 75% 75% 76% 75% 75%
Methane (CH4) 19% 18% 18% 16% 16% n/a 18%
Nitrous Oxide (N2O) 7.9% 7.9% 7.4% 6.9% 6.2% n/a 4.0%
Sub-total CH4 and N2O 27% 26% 25% 23% 22% n/a 22%
SUB-TOTAL CO2, CH4, and N2O 99% 99% 100% 98% 98% n/a 98%
F-Gases 0.4% 0.7% 0.8% 1.3% 2.0% n/a 2.0%

* Figures for 1970-2010 were pulled from Figure TS.1 (p. 42) of (IPCC, 2014);

^ The 2018 figures were pulled from (UNEP, 2019).

How many greenhouse gases are there?

For the full (itemized) list of greenhouse gases (GHGs) summarized below, refer to "Appendix 8.A, Lifetimes, Radiative Efficiencies and Metric Values" of IPCC WGI AR5 (2013).[5] Note: There are 207 GHGs if fossil and non-fossil Methane (CH4) is treated as two separate gases; and 206 if fossil and non-fossil CH4 is treated as the same gas.

All greenhouse gases[6]
Greenhouse Gas (GHG) Abbrev. Number of gases
Carbon dioxide CO2 1
Methane (non-fossil)[7] CH4 1
Methane (fossil)[7] CH4 1
Nitrous Oxide N2O 1
Chlorofluorocarbons[8] CFCs* 6
Hydrochlorofluorocarbons[8] HCFCs* 13
Hydrofluorocarbons HFCs** 39
Chlorocarbons and Hydrochlorocarbons n/a 6
Bromocarbons, Hydrobromocarbons and Halons n/a 10
Perfluorocarbons and Sulphur Hexafluoride ("Fully Fluorinated Species") PFCs and SF6** 23
Halogenated Alcohols and Ethers ("halons")[8] n/a (halons)* 106
TOTAL[7] n/a 206

* CFCs, HCFCs, and halons (for which F-gases are substitutes) are being phased out under the Montreal Protocol.[8]

** HFCs, PFCs (Nitrogen trifluoride is accounted for in this sub-group), and SF6 are termed F-gases (used "mainly as substitutes for ozone-depleting substances such as CFCs, HCFCs and halons.[8]

References

  1. 1.0 1.1 Note: Percentage figures for year 2018 originate from the EGR2019. All other percentages originate from the AR5 (specifically, from figure SPM.1 on p. 7). Source: IPCC, 2014: Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kreimann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)] Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  2. Gillenwater, Michael. June 15, 2010. "What Are Greenhouse Gases?" GHG Management Institute, 2008-2019. Accessed: 2019/10/20; Archived: 2019/10/20. [1]
  3. Note: Non-CO2 greenhouse gas emissions were backed into using YR2018 annual greenhouse gas emissions, 55.3 GtCO2e, from EGR2019, deducting Fossil emissions (37.5 GtCO2) and LUC emissions (7% or 3.9 GtCO2). Resulting in 13.9 GtCO2e sub-total for Methane (CH4), Nitrous oxide (N2O), and Fluorinated gases combined (which is 25.2% of GHGs). Percentages for the non-CO2 GHGs have not yet been added to this table. Source: United Nations Environmental Programme (2019). Emissions Gap Report 2019. UNEP, Nairobi.
  4. IPCC, 2022: Summary for Policymakers. In: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.001.
  5. Note: Refer to Appendix 8.A., Lifetimes, Radiative Efficiencies and Metric Values; Table 8.A.1. Source: IPCC, 2013: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the International Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  6. Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Kock, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakjima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifith Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  7. 7.0 7.1 7.2 There are 207 greenhouse gases (GHGs) if accounting for two (2) types of Methane gas (fossil and non-fossil); and 206 GHGs if accounting for both fossil and non-fossil methane as a single GHG.
  8. 8.0 8.1 8.2 8.3 8.4 Note: CFCs, HCFCs and Halogenated Alcohols and Ethers (i.e., Halons) are being phased out as per the Montreal Protocol and EU Legislation. Source: European Commission. "Fluorinated greenhouse gases." <https://ec.europa.eu/clima/policies/f-gas_en>. Accessed: January 6th, 2020.