Last reviewed on May 6, 2015

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. The 2020 GHG emissions limit is 431 million metric tonnes of carbon dioxide equivalent (MMTCO2e).

ARB Board Approval

Update to the 2020 Limit - 2014

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. The Board approved 431 MMTCO2e as the 2020 emission limit with the approval of the First Update to the Scoping Plan on May 22, 2014.

Original 2020 Limit - 2007

ARB staff constructed a 1990-2004 greenhouse gas emission inventory to determine the 1990 emission level, which the Board approved as the 2020 limit of 427 MMTCO2e. This value was based on IPCC second assessment report global warming potentials. The Board approved the 2020 limit on December 6, 2007. All materials related to 2007 board approval of the original 2020 limit can be found in the board approval page. This value was updated in the 2014 Scoping Plan Update.

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.