In 2006, California set a goal to reduce the state’s greenhouse gas emissions to 1990 levels by 2020. In 2016 California committed to a 40% reduction in greenhouse gases below 1990 levels by 2030, and 80% below 1990 levels by 2050.

A key element of California’s climate plan has been the state’s cap-and-trade program, which sets a statewide limit on sources responsible for 85 percent of California’s greenhouse gas emissions, and establishes a price signal needed to drive long-term investment in cleaner fuels and more efficient use of energy.

Carbon pollution declined as their economy boomed.

And, in September 2018, Governor Brown went further committing the state to carbon neutrality by 2045, achieving negative emissions thereafter; to clean transportation by reducing petroleum use 45% by 2030; to goals for 5 million electric vehicles by 2030; to 100% clean energy by 2045, to double the rate of energy efficiencies in buildings, and to extend and improve the state’s cap-and-trade program (additionally directing the revenues to greenhouse gas reducing programs which benefit disadvantaged communities).

Calling climate change “a threat to human existence, ”Governor Brown said, weeks before leaving office in 2018, “I’d say California has taken more intelligent action on climate change than any state or province in the Western Hemisphere.”

Brown’s successor as governor, Gavin Newsom, has proposed at least two new ideas beyond Brown’s. The first is to financially penalize city governments that discourage or prohibit housing development close to city centers and mass transit. This is intended to reduce driving and also protect planted land at risk of development.  The second is to restore discontinued funding for the Healthy Soils Initiative, an effort to get the soil to soak up carbon from the air. 

In July, 2020 data from the California Energy Commission estimated that in 2019, 36% of the state’s retail electricity sales were provided by renewable sources such as solar and wind. When sources of carbon free energy such as large hydroelectric generation and nuclear were included, that number reached 63%. They are ahead of schedule with a goal of 100% by 2045.

California is one of twenty five  states committed to the U.S. Climate Alliance, which is working to implement policies that advance the goals of the Paris Agreement.