GHG Global Warming Potentials

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Each greenhouse gas (GHG) has a global warming potential (GWP) value, which reflects the relative warming effect of a GHG over a specified period of time compared to the same mass of carbon dioxide. This metric allows emissions of different GHGs to be converted into the same emissions unit, carbon dioxide equivalents (CO2e). GWPs are calculated by the Intergovernmental Panel on Climate Change (IPCC) based on the intensity of infrared absorption by each GHG and how long gases remain in the atmosphere. GWPs are updated periodically with improvements to the underlying science. GWPs are also calculated using a set time horizon.  

California’s Assembly Bill 32 Greenhouse Gas Emissions Inventory (Inventory) currently uses 100-year GWPs from the IPCC’s Fourth Assessment Report. The 2013 and prior versions of the Inventory used 100-year GWPs from the IPCC’s Second Assessment Report. GWPs from the IPCC's Fifth Assessment Report (2013) and Sixth Assessment Report (2021) are available from U.S. EPA's National GHG Inventory [pdf].

100-year GWPs from the IPCC's Second (SAR) and Fourth (AR4) Assessment Reports

Gas NameFormulaSAR GWPAR4 GWP1
Carbon DioxideCO211
MethaneCH42125
Nitrous OxideN2O310298
Sulphur HexafluorideSF623,90022,800
Nitrogen TrifluorideNF3n/a17,200
Hexafluoroethane (PFC-116)C2F69,20012,200
Octafluoropropane (PFC-218)C3F87,0008,830
Octafluorocyclobutane (PFC-318)C4F88,70010,300
Tetrafluoromethane (PFC-14)CF46,5007,390
Hydrofluorocarbon 125HFC-1252,8003,500
Hydrofluorocarbon 134aHFC-134a1,3001,430
Hydrofluorocarbon 143aHFC-143a3,8004,470
Hydrofluorocarbon 152aHFC-152a140124
Hydrofluorocarbon 227eaHFC-227ea2,9003,220
Hydrofluorocarbon 23HFC-2311,70014,800
Hydrofluorocarbon 236faHFC-236fa6,3009,810
Hydrofluorocarbon 245faHFC-245fan/a1,030
Hydrofluorocarbon 32HFC-32650675
Hydrofluorocarbon 365mfcHFC-365mfcn/a794
Hydrofluorocarbon 43-10meeHFC-43-10mee1,3001,640

1AR4 GWPs are used for the current edition of the Inventory.