Last reviewed on May 13, 2014

California 1990 Greenhouse Gas Emissions Level and 2020 Limit

The current 2020 GHG emission limit is 431 MMTCO2e using IPCC Fourth Assessment Report GWPs


The Global Warming Solutions Act of 2006 (AB 32) requires that the Air Resources Board determine the statewide greenhouse gas emissions level in 1990. The act also requires that the Board approve a statewide greenhouse gas emissions limit, equal to the 1990 level, as a limit to be achieved by 2020. This limit is an aggregated statewide limit, rather than sector- or facility-specific.


Original 2020 Limit

ARB staff constructed a 1990-2004 greenhouse gas emission inventory to determine the 1990 emission level and 2020 limit of 427 million metric tonnes of carbon dioxide equivalent (MMTCO2e), using IPCC second assessment report global warming potentials. The Board approved the 2020 limit on December 6, 2007. All materials related to board adoption of the original 2020 limit can be found in the 1990 archive page.

Updates to the 2020 Limit

Calculation of the original 1990 limit approved in 2007 was revised using the scientifically updated IPCC 2007 fourth assessment report (AR4) global warming potentials, to 431 MMTCO2e. Thus the 2020 GHG emissions limit established in response to AB 32 is now slightly higher than the 427 MMTCO2e in the initial Scoping Plan.

Development of the Original 2020 Limit

The staff report titled "California 1990 Greenhouse Gas Emissions Level and 2020 Emissions Limit" discusses the original development of the 1990 statewide emissions level and provides a summary of the key emissions sources, the methodologies used to calculate the emissions, and the sources of data. These methods use the original IPCC second assessment report GWPs.