Last reviewed on June 17, 2016

Global Warming Potentials

Background

Each greenhouse gas (GHG) has a global warming potential (GWP) value, which reflects the climate forcing of a kilogram of emissions relative to the same mass of carbon dioxide (CO2). This number is calculated by the Intergovernmental Panel on Climate Change (IPCC), based on the intensity of infrared absorption by each GHG and how long emissions remain in the atmosphere. GWPs are calculated using a set time horizon. All GWPs used for GHG inventory purposes are considered over a 100-yr timeframe. GWPs are updated periodically with improvements to the underlying science.

100-yr GWPs from the IPCC second assessment report (SAR) and fourth assessment report (AR4).

AR4 GWPs are used for the 2000-2014 emission inventory

Gas Name Formula Lifetime (years) SAR GWP AR4 GWP Percent Change
Carbon Dioxide CO2 1 1
Methane CH4 12 21 25 +19%
Nitrous Oxide N2O 114 310 298 -3.9%
Sulphur Hexafluoride SF6 3200 23,900 22,800 -4.6%
Nitrogen Trifluoride NF3 740 n/a 17,200
Hexafluoroethane (PFC-116) C2F6 10,000 9,200 12,200 +33%
Octafluoropropane (PFC-218) C3F8 2,600 7,000 8,830 +26%
Octafluorocyclobutane (PFC-318) C4F8 3,200 8,700 10,300 +18%
Tetrafluoromethane (PFC-14) CF4 50,000 6,500 7,390 +14%
Hydrofluorocarbon 125 HFC-125 29 2,800 3,500 +25%
Hydrofluorocarbon 134a HFC-134a 14 1,300 1,430 +10%
Hydrofluorocarbon 143a HFC-143a 52 3,800 4,470 +18%
Hydrofluorocarbon 152a HFC-152a 1 140 124 -11%
Hydrofluorocarbon 227ea HFC-227ea 34 2,900 3,220 +11%
Hydrofluorocarbon 23 HFC-23 270 11,700 14,800 +26%
Hydrofluorocarbon 236fa HFC-236fa 240 6,300 9,810 +56%
Hydrofluorocarbon 245fa HFC-245fa 8 n/a 1,030
Hydrofluorocarbon 32 HFC-32 5 650 675 +3.8%
Hydrofluorocarbon 365mfc HFC-365mfc 9 n/a 794
Hydrofluorocarbon 43-10mee HFC-43-10mee 16 1,300 1,640 +26%

AR4 GWPs for 2016 Edition GHG Inventory

The ARB uses 2007 IPCC AR4 GWPs for the 2000-2014 emission inventory. Some previous versions of the inventory used GWPs from the SAR; the GWP version is documented in all archive datasets. A summary of the SAR versus AR4 GWPs are included in the table above.

Implications of Updated GWPs

GWPs are used to convert GHG emission values to "carbon dioxide equivalent" (CO2e) units. The percent change in GWP (above) will be mirrored in all CO2e emissions.



For general questions regarding California's Greenhouse Gas Emission Inventory, please contact: Anny Huang, Manager, Emission Inventory Analysis Section, Phone: (916) 323-8475

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