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Greenhouse Gases
Learn about key air pollutants causing global climate change, and their emissions inventories.
Pollutant Definitions
Many air pollutants have a warming influence on the climate. The Air District prepares emissions inventories of greenhouse gases, or GHGs, known to contribute significantly to climate change, including:
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (N2O)
- Hydrochlorofluorocarbons (HCFCs)
- Perfluorocarbons (PFCs)
- Chlorofluorocarbons (CFCs)
- Hydrofluorocarbons (HFCs)
- Sulfur hexafluoride (SF6)
To learn more about these and other pollutants in the Bay Area you can use the Pollutant Glossary provided by the California Air Resources Board (CARB).
Regional Emissions Inventory
An overview of the San Francisco Bay Area’s emissions inventory of greenhouse gases from years 1990 to 2050 is provided in the Bay Area Emissions Inventory: Summary Report for Greenhouse Gases.
Wherever available, the most recent activity data or measured emissions were used for the regional inventory development. Emissions from the 2022 base year served as a general reference for estimating historical and projected emissions when activity data and/or measured emissions data were unavailable. The regional GHG inventory focuses on anthropogenic sources and excludes emissions from biogenic sources, although some biogenic emissions may result from human activities. The regional GHG emissions inventory categorizes anthropogenic emissions into six sectors:
- Transportation
- Industrial
- Electricity Generation
- Commercial and Residential
- Waste Management
- Agriculture
The regional GHG emissions inventory is a production-based inventory that aggregates emissions generated within the Bay Area air basin by county, independent of where the resulting products, goods and services are consumed.
Inventory Updates (version: Base Year 2022, updated: August 2025)
A few key inventory updates and improvements in the current version of the emissions inventory include:
- The regional inventory reflects a comprehensive update of emission factors, activity data, controls, forecasting techniques, and methodologies for most GHG emissions sources, consistent with approaches used by California Air Resources Board (CARB).
- Estimated emissions were verified through comparisons with available emissions data from US Environmental Protection Agency or other data sources, and were adjusted using real word data as appropriate. For example, on-road vehicle emissions relied on CARB’s energy-based emission factors and fuel consumption rates adjusted by real-world fuel sales and statewide fuel mix.
- Future year emissions were developed using updated growth profiles based on the most recent population, household, and employment projections.
- An improved backcasting approach involving mathematical extrapolation of emissions derived from CARB datasets and GHG source-specific activity growth profiles has been applied to generate historical emission estimates for several source categories.
Current Inventory Reports, Data, and Documents
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Emmisions Inventory SummaryGet an overview of the regional inventory of GHG pollutants in the nine-county Bay Area
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Emissions Lookup ToolGet an illustrative breakdown of emissions by pollutant, year, source sector and sub-sector
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Emissions Assessment & ResearchGet a glimpse into research projects and studies that the agency is using to improve knowledge of emissions inventories
Archived Reports, Data, and Documents
- Bay Area Emissions Inventory Greenhouse Gas Emissions and Forecasts: Base Year 2015
- Bay Area Emissions Inventory Summary Report for Greenhouse Gases: Base Year 2011
- Base Year 2011 Emissions Inventory Source Category Methodologies
- GHG Emissions Projections for 1990-2029 Data Tables: Base Year 2011
- GHG Emissions by Facility Data Table: Base Year 2011
- Base Year 2008 Emissions Inventory Source Category Methodologies
- Bay Area Emissions Inventory Summary Report for Greenhouse Gases: Base Year 2007
Last Updated: 4/1/2026