Bar chart of 2000 to 2013 GHG emissions by category as defined in the Scoping Plan. Click to enlarge.

California’s annual statewide greenhouse gas (GHG) emission inventory is an important tool for establishing historical emission trends and tracking the state’s progress toward the goal set by the Global Warming Solutions Act of 2006 (AB 32). The law set a target of reducing emissions to 1990 levels by 2020.

After rising during the 2000s, the state’s overall greenhouse gas emissions fell in 2008 as a result of the recession. The decline leveled off from 2009 to 2011 and increased by 2% in 2012, due in part to the closure of the San Onofre Nuclear Generating Station and a drop in hydropower generation. The drop in hydropower has now been completely replaced by in-state wind and solar power. The 2013 inventory shows a decline of 1.5 million metric tons in emissions compared with 2012.

Overall trends in the inventory also demonstrate that the carbon intensity of California’s economy, the amount of carbon pollution per million dollars of GDP, is declining. Carbon intensity has dropped 23% from the peak in 2001, and declined an average of 1.9% per year over the past four years as GDP grew 6.6% overall during the same period.

Per capita emissions continued their decline. Over the 2000 to 2013 period, per capita GHG emissions in California dropped from a peak of 14.0 tons per person in 2001 to 12.0 tons per person in 2013, a 14% decrease overall.

Emissions from most major economic sectors in California either declined or remained flat in 2013. Industrial emissions were about the same as in 2012, while the electric power sector showed a slight decrease from 2012.

Emissions from the transportation sector rose by a single percentage point compared to 2012, but are still down 11% from the peak year of 2007. The main source of the rise in transportation emissions was the increased use of diesel by trucks. Transportation remains the largest source of greenhouse gas emissions at 37% of total emissions.

The Air Resources Board is also tracking short-lived climate pollutants (methane, black carbon, fluorinated gases) and plans to release a strategic plan to reduce these pollutants later this year. These climate pollutants the potential to warm the atmosphere hundreds and even thousands of times more than CO₂. California is now focusing more intensely on reducing these gases because of the relatively quick reduction in warming which can be achieved.

The data in the inventory comes from a number of sources including California’s Mandatory Greenhouse Gas Reporting Regulation, the California Energy Commission, and the US Energy Information Administration.

California has developed an integrated set of programs to meet the greenhouse gas reduction goals of AB 32. The primary programs are the Renewable Portfolio Standard, the Advanced Clean Cars program, the Low Carbon Fuel Standard, and the Cap-and-Trade program. Reductions also result from numerous energy efficiency and conservation programs.

Governor Edmund G. Brown, Jr. recently established a 2030 greenhouse gas reduction goal of 40% below 1990 levels, an interim target toward meeting the 2050 goal of reducing emissions 80% below 1990 levels.

California has also joined with a growing list of states and provinces from around the world in an agreement to limit global warming to less than 2 degrees Celsius. To date, 14 states have signed the so-called “Under 2 MOU.”