According to the most recent greenhouse gas emissions inventory from the California Air Resources Board (ARB), the state’s total greenhouse gas emissions rose 1.7% in 2012 from 2011 to 459 million tonnes of carbon dioxide equivalent (MMTCO2e).

According to ARB, the increase was driven primarily by strong economic growth in the state; the unexpected closure of the San Onofre Nuclear Generating Station (SONGS); and drought conditions that limited in-state hydropower generation. Since 2000, GHG emissions have decreased by 1.6% (from 466 to 459 MMTCO2e) after reaching a peak of 493 MMTCO2e in 2004.

In 2012, the transportation sector was the largest source of emissions in California, accounting for approximately 37% of the total emissions.

On-road vehicles accounted for more than 90% of emissions in the transportation sector. However, transportation related GHG emissions have dropped 11% since 2006. The industrial sector accounted for approximately 22% of the total emissions. Emissions from electricity generation were about 21% of total emissions, with higher contribution from in-state than from imported electricity.

Per capita emissions in California have decreased by 12% from 2000 to 2012, in spite of the overall 11.4% increase in population during the same period. Per capita emissions from in-state electricity generation have declined by 22% from 2000 to 2012.