A group of the world’s leading climate scientists are warning governments and the livestock industry against adopting an “accounting trick” that will imperil the all-out global effort required to control heat-trapping emissions.
In the statement, 42 scientists call on the government of Ireland, a major dairy producer, to reject a proposal that would allow it to use what’s known as Global Warming Potential Star, or GWP*, to measure methane emissions. The scientists say the methodology, which was initially developed to more accurately measure the warming impact of different greenhouse gases, is being misused by the livestock industry and livestock-heavy countries to weaken requirements for reducing the powerful, short-lived greenhouse gas that comes mainly from livestock.
Major emitters, including the United States and the European Union, along with other major cattle countries, including Brazil and Argentina, are promoting GWP* to revise climate targets, aiming for “temperature neutrality” or “no additional warming” rather than substantially cutting emissions. These targets, the scientists say, will allow the beef and dairy industries, which are responsible for the bulk of global methane, to continue emitting huge quantities of methane.
“What worries us as scientists is that other countries are now seriously weighing these targets. The danger is that one country adopts them, then the next, and the next,” said Paul Behrens, an environmental scientist at the University of Oxford and co-author of the letter. “That’s a huge problem, because the direction we need to be heading is deep methane cuts that actually pull near-term warming down. A ‘no additional warming’ target does the opposite: It freezes today’s high emissions in place and throws away the fastest cooling lever we have.”
If Ireland adopts its goal of “temperature neutrality” by using GWP* in its carbon budget for 2031 to 2035, it will allow the country to emit 9 million more tons of carbon dioxide equivalent, the scientists say, roughly the same as burning 20 million barrels of oil. New Zealand, another dairy giant, was the first country to adopt a “no additional warming” target, in 2025, employing the GWP* methodology, which led to a weakening of its methane reduction target.
The Intergovernmental Panel on Climate Change and governments, including those that signed onto the Paris Agreement, use a metric called GWP 100 to measure the cumulative impacts of emissions over a 100-year period, relative to carbon dioxide. GWP* measures the warming impact of changes in the rate of emissions between two points in time and was developed to understand the impact of shorter-lived greenhouse gases, including methane, which only lasts in the atmosphere for 10 or 12 years.
But the signing scientists, who include high-profile climate researchers Michael Mann and Drew Shindell, say that using a baseline—a point in time—allows countries to write off the impact of existing cattle or dairy herds.
“This a real serious misuse of GWP* because it’s designed to look at the temperature impacts of future projections,” said Shindell, a climate scientist at Duke University. “But if you want to look at the responsibility of any particular nation or sector, or sector within a nation, like livestock from Ireland, the contribution is their current emissions relative to what they were centuries ago.”
Concentrations of methane in the atmosphere are roughly two-and-a-half times higher than they were before industrialization. Methane is responsible for about one-third of global warming.
“We have a lot more cows than we did then, and that methane from those cows is much higher now,” Shindell noted. “That’s contributed quite a lot to climate change—about half a degree to around 2020.”
The scientists stressed that GWP* gives a free pass to countries with large existing herds, while developing countries with historically smaller livestock herds and less industrial livestock production will be penalized when they increase emissions from a lower baseline.
“It’s a question of equity,” Shindell said. “You get a reward for being a high emitter. If you currently have very high methane emissions, you get to keep them. And that’s typically wealthy countries like the United States and many others, with a lot of livestock.”
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Georgina Gustin covers agriculture for Inside Climate News, and has reported on the intersections of farming, food systems and the environment for much of her journalism career. Her work has won numerous awards, including the John B. Oakes Award for Distinguished Environmental Journalism, and she was twice named the Glenn Cunningham Agricultural Journalist of the Year, once with ICN colleagues. She has worked as a reporter for The Day in New London, Conn., the St. Louis Post-Dispatch and CQ Roll Call, and her stories have appeared in The New York Times, Washington Post and National Geographic’s The Plate, among others. She is a graduate of the Columbia University Graduate School of Journalism and the University of Colorado at Boulder.