Greenhouse Gas (GHG)

Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic (human-caused), that absorb and emit radiation at specific wavelengths within the infrared spectrum emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This ability to absorb and re-emit causes the greenhouse effect, trapping heat in Earth’s atmosphere. Water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ozone (O3) are the primary GHGs in the Earth’s atmosphere. There are also a number of entirely human-made GHGs in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, managed under the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol). Besides CO2, N2O and CH4, the Kyoto Protocol deals with the GHGs sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).

Source: Concepts; J Wilcox, B Kolosz, & J Freeman (2021) CDR Primer

Global Warming Potential (GWP)

Greenhouse Gas Formula 100-year GWP (AR4)
Carbon dioxide CO2 1
Methane CH4 25
Nitrous oxide N2O 298
Sulphur hexafluoride SF6 22,800
Hydrofluorocarbon-23 CHF3 14,800
Hydrofluorocarbon-32 CH2F2 675
Perfluoromethane CF4 7,390
Perfluoroethane C2F6 12,200
Perfluoropropane C3F8 8,830
Perfluorobutane C4F10 8,860
Perfluorocyclobutane c-C4F8 10,300
Perfluoropentane C5F12 13,300
Perfluorohexane C6F14 9,300

NOTE: The GWP values were changed in 2007. The values in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) in 2007 were refined from the IPCC Second Assessment Report (SAR) values used previously and still in much of the literature. –

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