As countries prepare for the United Nations climate summit in Turkey next month, researchers are questioning how methane emissions from livestock are measured and reported. Two recent analyses argue that commonly used accounting methods can underestimate or obscure the climate impact of beef production.
Methane is a particularly important target for climate policy because it warms the atmosphere far more strongly than carbon dioxide over shorter periods, although it breaks down after roughly 12 years. Livestock is the largest human-related source of methane, making the way its emissions are calculated a subject of continuing debate.
A report published October 29 and commissioned by Greenpeace International examined a method known as global warming potential-star, or GWP*. The approach compares changes in methane emissions with an equivalent pulse of carbon dioxide, reflecting methane’s shorter atmospheric lifespan and different warming profile.
Scientists generally recognize the underlying science of GWP*, but critics say it can be misused to present limited methane reductions as major progress. The method may allow countries with historically high livestock emissions to claim “no additional warming,” climate neutrality or even negative emissions when their actual methane output remains high.
The Greenpeace analysis, based on modeling by consultancy Cerulogy, examined the 10 largest livestock-exporting countries that have pledged to cut methane emissions by 30 percent by 2030 under the Global Methane Pledge. It found that these countries, including Brazil and the United States, could reduce actual methane emissions by only 0.6 percent from 2020 levels while reporting a 30 percent reduction under GWP*.
The report estimated that achieving a genuine 30 percent reduction in methane would require the countries to cut the equivalent of 640 million metric tons of carbon dioxide emissions in 2030. Under GWP*, however, they could report 898 million metric tons of negative carbon dioxide emissions. The difference between the two accounting approaches would total 1,538 million metric tons of carbon dioxide for that year, according to the analysis.
In the United States, the study said livestock producers could report 218 million metric tons of negative carbon dioxide emissions under GWP*, despite emitting 178 million metric tons in 2030. The report compared that gap with the annual emissions of approximately 86 million cars.
Sophie Nodzenski, a Greenpeace campaigner, said the method benefits countries and industries that maintain methane emissions near a recent baseline rather than substantially reducing them. Jennifer Molidor of the Center for Biological Diversity described the approach as “creative accounting and fuzzy math.”
Livestock industry groups have supported a “split gas approach” based on GWP*, arguing that it better distinguishes between long-lived and short-lived greenhouse gases. Forty-two climate scientists warned earlier this year that using the method to set “no additional warming” targets could weaken efforts to reduce methane. New Zealand became the first country to adopt such a target last year, according to the report.
A separate study published October 11 in Frontiers in Sustainable Food Systems examined how methane accounting affects estimates for food emissions. Researchers from the University of California, Los Angeles, compared the 20-year and 100-year global warming potential metrics across 16 food categories and 222 food items.
They found that beef-based meals generated about 3,500 grams of carbon dioxide equivalent when assessed using GWP100, but more than 7,000 grams when assessed using GWP20. Most of the other foods in the study had broadly similar results under the two metrics.
The researchers said the findings show why policymakers and climate negotiators may need to use more than one metric when assessing the climate effects of food production. Jennifer Jay, one of the study’s authors, said the figures demonstrate a substantial difference between beef and other protein sources.
Sources: Inside Climate News.