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CO2 equivalents

Charts and tables in this emissions section of our website convert all greenhouse gas (GHG) emissions into CO2 equivalents so they can be compared.

Each greenhouse gas (GHG) has a different global warming potential (GWP) and persists for a different length of time in the atmosphere.

The three main greenhouse gases (along with water vapour) and their 100-year global warming potential (GWP) compared to carbon dioxide are: (1)

  • carbon dioxide (CO2) - 1 x
  • methane (CH4)         - 25 x more powerful
  • nitrous oxide (N2O) - 298 x more powerful

Water vapour is not considered to be a cause of man-made global warming because it does not persist in the atmosphere for more than a few days.

There are other greenhouse gases which have far greater global warming potential (GWP) but are much less prevalent. These are sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).

There are a wide variety of uses for SF6, HFCs, and PFCs but they have been most commonly used as refrigerants and for fire suppression. Many of these compounds also have a depleting effect on ozone in the upper atmosphere.

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Global Warming Potential (GWP) table

The following table shows the (GWP) for greenhouse gases reported by the United Nations Framework Convention on Climate Change (UNFCCC). (1)

Click here to download an expanded PDF table (144 kB)


Greenhouse Gas Formula 100-year GWP (SAR) 100-year GWP (AR4)
Carbon dioxide CO2 1 1
Methane CH4 21 25
Nitrous oxide N2O 310 298
Sulphur hexafluoride SF6 23,900 22,800
Hydrofluorocarbons (HFCs)
HFC-23 CHF3 11,700 14,800
HFC-32 CH2F2 650 675
Perfluorocarbons (PFCs)
Perfluoromethane CF4 6,500 7,390
Perfluoroethane C2F6 9,200 12,200
Perfluoropropane C3F8 7,000 8,830
Perfluorobutane C4F10 7,000 8,860
Perfluorocyclobutane c-C4F8 8,700 10,300
Perfluoropentane C5F12 7,500 13,300
Perfluorohexane C6F14 7,400 9,300


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