Greenhouse Gases

The District has also prepared an emission inventory of pollutants contributing to climate change, or greenhouse gases (GHG). The Greenhouse Gas Source Inventory estimates direct and indirect emissions from sources within the District’s jurisdiction for the following gases: carbon dioxide, methane, nitrous oxides, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.

This emissions inventory estimates GHG emissions produced by the San Francisco Bay Area in 2007. This inventory updates the Air District's previous GHG emissions inventory for base year 2002 (published November 2006). All activity data has been updated to reflect more current industrial activity, motor vehicle travel, and economic and population growth. Most of the methodologies for calculating emissions remain the same, with certain exceptions: 1) emissions from electricity consumed in the Bay Area but generated outside the region are now included; 2) emissions for high global warming potential gases such as Hydrofluorocarbons and Perfluorocarbons used as refrigerants etc. are now included; 3) more complete oil refinery process emissions are included in this inventory; 4) certain off-road equipment, such as construction and industrial, was previously included in the transportation sector and is now reported separately; 5) ship emissions are now calculated for travel within 100 miles of California's coastline rather than 3 miles to be consistent with the Air District's criteria pollutant inventory and; 6) biogenic CO2 emissions are calculated but not included in the total CO2 equivalent estimates for the region.

Because of these revisions, caution should be used in comparing this 2007 GHG inventory to the previous 2002 inventory. These revisions have resulted in different estimates of Bay Area GHG emissions. Consequently, the percentage contributions from individual sectors may be affected. For example, estimates of transportation emissions have not changed significantly between the two inventories, but the percentage from the transportation sector has changed because the estimated total emissions are greater in the updated inventory (due mainly to increased estimated emissions resulting from the revisions summarized above). Such ongoing updates are typical of emission inventories. Examining emission forecasts and backcasts in a single emission inventory is more useful in determining trends than comparing one inventory against another.

View the updated Source Inventory of Bay Area Greenhouse Gas Emissions (2007 Base Year).