UC Davis air-quality scientist and global authority on livestock emissions, Dr. Frank Mitloehner, was prominently featured in a recent Carbon Brief analysis, where he offered expert insight into the worldwide debate over how methane’s climate impact should be measured.

Carbon Brief is a UK-based website that cover climate science, climate policy and energy policy.

The article focuses on GWP*, or global warming potential star, a relatively new metric designed to better reflect how short-lived greenhouse gases like methane warm the planet. Unlike carbon dioxide, which can linger in the atmosphere for centuries, methane breaks down after about 12 years. GWP* accounts for that decay, distinguishing between increasing and stable methane emissions — a difference that traditional 100-year calculations often miss.

Dr. Mitloehner, who is Director of the UC Davis CLEAR Center, has long championed the use of GWP* in climate accounting. He argues it gives a more accurate picture of livestock’s contribution to warming by recognizing that methane from cattle — known as biogenic methane — is part of a natural carbon cycle, not a one-way addition of new carbon like fossil fuels.

“It’s an urban myth that biogenic methane isn’t a concern,” he told Carbon Brief.

Dr. Mitloehner’s research has shown that if livestock methane declines by roughly 0.3% a year — about 10% per generation — it causes no additional warming. That finding has bolstered claims that sectors like California’s dairy industry could reach “climate neutrality” within the next decade.

Not everyone agrees. Several climate scientists told Carbon Brief that while GWP* may be scientifically valid for measuring temperature changes, it risks confusing policymakers and the public. Critics argue it could allow agricultural emitters to appear climate-neutral even while maintaining significant methane output.

Some have said that “GWP* can easily be used as a ‘get-out-of-jail-free’ card.

Dr. Mitloehner disputes that criticism, saying the goal is clarity, not leniency. “If you reduce emissions, it makes your contributions look less. If you increase emissions, it makes your contributions much worse," he said. 

While Dr. Mitloehner recognizes that questions around the fairness of using GWP* are legitimate policy concerns, he maintains that, from a scientific standpoint, the approach is sound and not subject to significant dispute.

The Carbon Brief story comes as countries like New Zealand and Ireland weigh whether to adopt GWP* in national climate reporting — decisions that could reshape global methane policy. 

While the debate over the metric continues, Mitloehner’s visibility in the discussion underscores his influence on how the world measures, and manages, agriculture’s role in climate change.