California’s Dirty Environmental Secret

Deborah Gordon
Sep 5, 2018 · 4 min read

Written by Deborah Gordon & Jonathan Koomey

California Oil Fields, 1909, Photo credit:, Public Domain,

As California’s Global Climate Action Summit gets underway to “take ambition to the next level,” there’s no better time for Governor Brown to come clean on the state’s dirty oil.

California’s oil is among the dirtiest in the world, but it’s difficult to assess just how dirty — and how to clean it up — because policymakers aren’t collecting enough information about the quality of the oil produced, refined, and imported into the state. Oil data transparency is critical. And as the New York Times editorial board recently published, “in California, facts and science still matter.”

Using an open-source tool — Oil Climate Index — developed with partners from Stanford and the University of Calgary, we assess that the lifecycle greenhouse gas emissions from a barrel of California’s Midway Sunset oil, the state’s largest producing field, has 44 percent higher total greenhouse gas emissions than light, conventional oils. And in terms of their indirect emissions from production and refining alone, the dirtiest oils in California were estimated to be five times more carbon intensive than Texas’ lower-emitting oil. This assessment used the only open source data on record that dates back to 1978. Reassessing Midway Sunset’s lifecycle emissions using newer, yet incomplete, decade-old data indicates that its carbon intensity could be even higher than Canadian oil sands.

This should not be news.

A century ago, long before climate change was a major concern, U.S. government experts warned that California’s oil was complex and challenging to handle. Reports dating back to 1919 acknowledge that Midway Sunset contains low quality oil and called for in-depth studies and ongoing analysis of Midway Sunset, a recommendation that applies equally to many California oils.

If such consistent data collection ever happened — which does not appear to be the case — it was never shared publicly. Today, Californians remain largely in the dark when it comes to their oil’s true characteristics. No state agency keeps an inventory, tracks, or discloses oil quality (referred to as an oil assay).

Oil quality directly affects the environment. California’s century-old oil fields require more energy to extract and refine each barrel, making California crude some of the world’s most environmentally damaging. In terms of their extraction alone, the California Air Resources Board estimates that the carbon intensities (CI) of in-state oil production range by over an order of magnitude, from a high of 31 grams carbon dioxide equivalent per megajoule (Placerita, east of Los Angeles) to a low of just under 2 (Wayside Canyon, near Santa Clarita).

Midway Sunset’s production CI registers at 25, near the top of this range. But this carbon intensity score does not take into account the extra emissions from refining this oil to turn it into gasoline, diesel, petroleum coke, and other petroleum products, which also varies with oil quality.

Midway Sunset Oil Field, 2008, Photo credit: Antandrus,

Californians have a right to know about the characteristics and environmental impacts of the oil produced and refined in their state. And now that the federal government is compelling the state to weaken its auto standards and use more oil, collecting and disclosing these oil quality data are paramount.

New knowledge about different oils’ lifecycle climate impacts could be used to design even smarter oil policies. The lack of data creates a major blind spot for California policymakers, who have long focused their attention more on reducing oil demand than managing oil supplies (and that finding is true more broadly).

With greater transparency, however, California’s leaders would have the information they need to craft innovative policies to reduce greenhouse gas emissions from the state’s oil sector. For example, the legislature can promote renewable energy to generate steam for enhanced oil extraction, push for use of renewable hydrogen in oil refining, curtail petroleum coke exports, pair electric vehicle adoption with oil refinery capacity reduction, and create a gold-standard public oil data transparency regime.

California is home to the Monterey formation, one of the largest oil plays in the world. What’s more, Midway Sunset (and other carbon intensive oil fields) may have billions of barrels of oil remaining in place, with the potential to emit several gigatonnes of carbon dioxide. Without up-to-date information, there’s no way the state can provide effective environmental oversight on its massive oil resources when Washington is driving oil and climate policy.

Deborah Gordon (@dxgordon) is Director of the Energy and Climate Program at the Carnegie Endowment for International Peace and Senior Fellow at Brown University’s Watson Institute for International and Public Affairs. Jonathan Koomey, Ph.D. (@jgkoomey) has been studying climate solutions for more than three decades.

Deborah Gordon

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Deborah Gordon is director of Carnegie’s Energy and Climate Program, where her research focuses on oil and climate change issues in North America and globally.