GHG Global Warming Potentials
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Each greenhouse gas (GHG) has a global warming potential 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 current 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 the Inventory
CARB uses 2007 IPCC AR4 GWPs for the current emissions 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.