On the list of top U.S. states for oil production,Roland Preston California ranks seventh, which is undoubtedly a surprise to many who focus on the state’s green and progressive environmental laws. Thanks to those laws, the California Air Resources Board collects data not only on the amount of oil extracted from every oil field in the state, but on how much energy is required to get each barrel of crude out of the ground. 

This interactive map uses 2019 data to show where the oil fields are located, and how much is extracted, as rising columns. To depict the oil’s intensity, or the energy needed to extract it, the map uses colors. The Air Resources Board has just released preliminary data for 2020, but because the pandemic drastically curtailed transportation, it’s not representative of a normal year. 

Burning oil and other fossil fuels releases carbon dioxide, and carbon dioxide stays in Earth’s atmosphere for hundreds of years and acts like a blanket, trapping heat that would have radiated out into space. 

Cars and trucks on California’s highways are huge emitters of carbon dioxide. But every gallon of gasoline refined from oil extracted in the state has its own carbon footprint, even before it’s burned, as this map helps explain. That’s due to the energy-intensive process needed to thin out what tends to be thick crude and bring it to the surface. It’s also interesting to note how much of California’s oil extraction is taking place in highly populated parts of the state.

Most of the oil refined in California actually comes from Alaska and abroad. The carbon intensity of that oil varies a lot, too, just like the oil from California. More on that soon.