California Dairy CLEAR Center

Methane, Cows, and Climate Change: California Dairy's Path to Climate Neutrality

UC Davis White Paper Re-Examines Methane’s Role in Climate Change, and How California Dairy Can Achieve Climate Neutrality

DAVIS, Calif., Sept. 2, 2020 Researchers from the University of California, Davis are rethinking methane and showing that climate neutrality is within reach for the California dairy sector.

Methane (CH4) is a potent greenhouse gas that is 25-28 times stronger than carbon dioxide (CO2) — the primary greenhouse gas driving climate change in California — but how it influences actual warming is much different, according to a white paper released today by UC Davis professors Frank Mitloehner, Ph.D., and Ermias Kebreab, Ph.D., along with Michael Boccadoro, executive director of Dairy Cares. The publication, Methane, Cows, and Climate Change: California’s Dairy’s Pathway to Climate Neutrality,” examines recent literature from leading climate scientists and its implications for the California dairy sector.

Download the Paper and Executive Summary

Methane is a short-lived climate pollutant and exists in our atmosphere for 12 years before it’s broken down. This means, when a constant rate of methane is emitted for more than 12 years, one molecule in effect replaces a previously emitted molecule that has since been removed. In other words, methane isn’t accumulating in the atmosphere. Currently, the main accounting method used for measuring the climate impacts of greenhouse gases does not describe how individual gases, such as methane warm — or cool — the climate over time. That oversight leads to a misinterpretation of methane’s role in warming the climate, while also ignoring possible solutions that could offset greenhouse gases from other sectors such as transport.

CLEAR Center Stock vs. Flow graphic
CO2 accumulates in the atmosphere, whereas methane flows through the atmosphere.
Credit: CLEAR Center at UC Davis. 

“We have been looking at methane incorrectly when it comes to reducing warming,” said Mitloehner, a professor and air quality specialist for Cooperative Extension in the Department of Animal Science at the University of California, Davis and head of the Clarity and Leadership for Environmental Awareness and Research (CLEAR) Center at UC Davis. “While more potent than the most prevalent greenhouse gas carbon dioxide, methane is a short-lived climate pollutant, staying in our atmosphere for about 12 years before it’s broken down and removed. On the other hand, carbon dioxide remains in our atmosphere for centuries, with new emissions accumulating on top of those previously emitted, making it the main driver of climate change.”

Frank Mitloehner at the UC Davis dairy. Credit: Joe Proudman / CLEAR Center. 

According to the white paper, which examined historic dairy production in that state, California dairy farms have already stabilized methane emissions, which is a critical step to achieving climate neutrality and global climate goals. The authors explain, that as dairies continue to achieve further methane emission reductions, then they can create negative warming, also referred to as “cooling.”

California — the fifth-largest economy in the world — is responsible for about 1 percent of all global greenhouse gas emissions. More than 80 percent of California’s greenhouse gas emissions come from fossil fuel uses such as the transportation (41 percent), industrial (23 percent) and power-generating (16 percent) sectors. Even though California is the United States’ largest agricultural producer— producing fruits, vegetables, nuts, livestock, and other essential foods for much of the nation and the world — the agricultural sector’s greenhouse gas contribution is roughly 8 percent of the state’s total greenhouse gas emissions. Of this, California’s largest-in-the-nation dairy sector accounts for 4 percent of the state’s total greenhouse gas emissions.

To its credit, the state has established goals for reducing greenhouse gas emissions by 40 percent by 2030, 80 percent by 2050, as it works toward a goal of “net-zero” carbon emissions by 2045.

Given greater efficiencies, plus a decrease in the number of cows and total milk production in recent years, the amount of methane emitted by California dairies is less today than in 2008. Simply put, California dairy farms are adding less methane today than they did 12 years ago, meaning more methane is being broken down than is being emitted into the atmosphere.

California’s dairy farmers are making further progress in reducing the amount of methane emissions released into the environment by installing anaerobic digesters designed to capture methane, or through other projects like compost pack barns and solid separators, which are designed to reduce methane production on farms. According to the California Department of Food and Agriculture, California dairies are implementing projects that will result in a 25 percent reduction in manure-related methane emissions since 2013.

California Dairy Digester
California climate-smart dairy with a digester, manure solid separator, and solar installation. Credit: Dairy Cares. 

Continued progress in these areas will be necessary for the state’s dairy production sector to reach the point at which they are no longer adding to global warming. This is known as climate neutrality.

“Reducing methane emissions and achieving climate neutrality is no small undertaking,” said Kebreab, who holds the Sesnon Endowed Chair in Sustainable Animal Agriculture in the Department of Animal Science at the University of California, Davis. “California is among the most efficient producers of milk and dairy products, and its life cycle carbon footprint (per gallon of milk produced) is among the lowest of any region in the world. Further reductions will be accelerated as dairy methane reduction projects are implemented and feed additives become widely available. For other dairy regions, a critical first step will be to achieve similar levels of production efficiency (more milk with fewer cows) to begin stabilizing methane emissions and work toward climate neutrality. The impact of such an accomplishment would have profound global climate effects.”

Ermias Kebreab UC Davis
Ermias Kebreab at the UC Davis dairy. Credit: UC Davis. 

The white paper identifies methane as an important mitigation opportunity. As well, it follows research on notable differences among individual greenhouse gases and their impact on climate change by leading scientists at the Oxford Martin School and Environmental Change Institute at the University of Oxford.

For media requests, please contact Joe Proudman, associate director for communications in the CLEAR Center, at

Media kit with images and graphics:

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The CLEAR Center, based in the UC Davis Department of Animal Sciences, brings clarity to the intersection of animal agriculture and the environment by conducting and communicating the latest research in livestock production and environmental sustainability. The CLEAR Center, which stands for Clarity and Leadership for Environmental Awareness and Research, is under the direction of Frank Mitloehner, animal science professor and air quality Cooperative Extension specialist. Catch up on CLEAR Center’s latest news and research at

Dairy Cares is a statewide coalition with a mission to ensure the long-term sustainability of California’s family dairy farms through planet-smart practices and responsible animal care. To learn more about California’s planet-smart, sustainable dairy practices, visit



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