Applying California's AB 32 targets to the regional level: A study of San Diego County greenhouse gases and reduction strategies

This paper presents a summary of a local effort in California to assess greenhouse gas (GHG) emissions and identify potential mitigation measures. Local policymakers in California already have been searching for ways to reduce GHG emissions but it was the California Global Warming Solutions Act of 2006 (AB 32), which seeks to reduce GHG emissions to 1990 levels by 2020, that has provided a framework for regions to evaluate their ability to reduce GHG emissions. We conducted a GHG inventory for the San Diego region from 1990 to 2006, with forecasts to 2020. The region emitted approximately 34 million metric tons of carbon dioxide equivalent (MMT CO2E) in 2006 from anthropogenic sources, which represents a 17% increase over the 1990 level of 29 MMT CO2E. Applying a combination of 21 existing or pending state GHG reduction mandates and feasible regional measures we show that the region could achieve the AB 32 target. Although the largest reductions are achieved through state mandates, all measures, including at the local level, will be required to achieve the AB 32 target. Thus local regions retain control over a fairly significant portion of reductions, and remain important actors in the implementation and compliance of state mandates.