California’s Greenhouse Gas Emissions and Trends over the Past Decade

In August 2000, the California Legislature mandated that the California Energy Commission (CEC) update California's state-level inventory of greenhouse gas (GHG) emissions by January 1, 2002. This paper discusses the results of this inventory development effort, including (a) the process of harmonization with data and research results from other California state agencies and institutions, (b) trends in California's GHG emissions from 1990-2000, and (c) ongoing efforts to improve and refine these emission estimates for a revised inventory (expected to be completed in late 2002). Previous GHG inventories for the state of California suggested that emissions remained relatively stable from 19901994. The results presented here extend the time series to 1999 and include estimates for several previously omitted source categories, including several types of industrial processes, various agricultural sources, and wastewater treatment. In addition, the inventory employs emission estimation methodologies that are consistent with the Emission Inventory Improvement Program guidance, the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-1999, and the Intergovernmental Panel on Climate Change (IPCC) guidance. By late summer 2002, CEC plans to further improve the data sources, emission factors, and methods to include emissions estimates for the year 2000, and to reflect 2000 IPCC Good Practice Guidance, methods from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2000, and results of ongoing research funded by the CEC.