Global Warming Potentials
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|
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