The world is moving in a dangerous direction when it comes to planet-warming methane emissions, which are rising to record levels driven largely by human activity, new research warns.
Although many people associate methane with cow belches and melting permafrost, a paper published this week in the journal Earth System Science Data found that global methane emissions over the past five years have increased faster than ever before, with at least two-thirds of those emissions now coming from human sources.
In April of this year, methane concentrations reached a record high of 1,931 parts per billion, an increase of 11 ppb compared to the previous year.
Experts say the results are deeply worrying, as they indicate that the planet is on track to far exceed the desired limit of 2.7 degrees of warming compared to the pre-industrial era, an international benchmark that is usually considered to be 1.5 degrees Celsius. In fact, methane contributed to almost 1 degree of global warming in the 2010s.
“In terms of the methane contribution, we’re on a trajectory that’s consistent with about 3 degrees C right now,” said Rob Jackson, the study’s lead author, who is also a climate scientist at Stanford and chair of the Global Carbon Project. “We’re far from 1.5 or even 2 degrees C when you consider methane alone.”
The 3 degrees Celsius (about 5.4 degrees Fahrenheit) scenario would have potentially disastrous consequences, including rapid melting of ice sheets, prolonged heat waves and droughts, water shortages, famine and political and social unrest, among other outcomes outlined by the Intergovernmental Panel on Climate Change.
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But while methane is 30 to 80 times more potent than CO2, ton for ton, it has one advantage: It's also relatively short-lived: methane lasts about a decade in the atmosphere, compared with CO2, which lasts hundreds of years, if not much longer.
“It’s really the only lever we have to slow warming over the next decade or two,” Jackson said. “We can’t really do anything about the trillions of tons of carbon dioxide in the air right now in that time frame, but in the case of methane, we could see concentrations return to preindustrial levels within a decade if we could just wave a magic wand to stop anthropogenic emissions.”
“That's not likely to happen soon,” he added, “but that should be our goal. If we do that, we'll get at least half a degree more.” [Celsius] of reduced warming”.
Sources of methane emissions can be divided into two categories: human sources, which come mainly from agriculture, fossil fuels, landfills and waste; and natural sources such as wetlands, swamps and bogs that release methane when bacteria decompose their organic matter.
The study found that emissions from both categories are increasing, though human sources appear to be generating an increasing share, now accounting for about 65% of estimated emissions, up from 60% in 2020, Jackson said. (The actual share may be even higher depending on how some sources, such as emissions from dams and reservoirs, are classified.)
However, there is also growing concern about methane emissions from natural systems.
Growing global temperatures are increasing microbial activity in tropical hotspots such as the Congo, the Amazon and Southeast Asia, which are releasing more methane that in turn could contribute to further warming in a worrying feedback loop, Jackson said.
“The fact that everything is still increasing is disconcerting. But what is most worrying to me is the possibility of increasing natural emissions, particularly in the tropics,” he said. “We think we are starting to see that, but we won’t know for sure in another four or five years, and that is very bad news if it starts to happen on a large scale.”
Arctic permafrost — or ground that was once permanently frozen — is also thawing amid record-breaking global temperatures, releasing carbon and methane into the atmosphere.
Evan Sherwin, a research scientist at Lawrence Berkeley Laboratory who was not involved in the study, said its findings are important and comprehensive, though not entirely surprising.
“It’s a pretty stark warning for us, especially considering that there have been so many efforts to mitigate methane emissions, that the proportion of methane emissions coming from human-caused sources appears to be increasing,” Sherwin said.
He said there was still a fair degree of uncertainty about the trajectory the planet would take in terms of warming, particularly since humanity still had a fair degree of control over its emissions between now and the end of the century.
Agriculture is one of several sources of man-made methane. Pictured here, Holstein cows fill a dairy farm in California.
(Mel Melcon/Los Angeles Times)
But if methane emissions continue to rise at roughly the current rate and CO2 emissions are not reduced as rapidly as needed, a 3 degree Celsius warming “doesn't seem all that far-fetched to me,” he said.
Like Jackson, he said the potential for increased emissions from natural sources is worrying and warrants further study, particularly around tropical ecosystems.
However, he noted that human-caused methane emissions are not increasing everywhere in the world. In Europe, for example, emissions have largely declined over the past two decades, while Korea, Japan and Australasia have remained more or less unchanged, the study shows. (Overall estimates for the United States indicate an overall increase over that period.)
“That's a sign that it's possible to keep methane emissions stable, or even reduce them substantially, which I think is a promising sign,” Sherwin said.
In fact, the finding that humans are now the main driver of methane emissions could be seen as a positive in some ways, as it is something that can potentially be mitigated or controlled, Sherwin added.
“It’s a huge tool we have to buy time,” he said. “If we take large-scale action to reduce methane emissions (and also nitrous oxide and other shorter-lived greenhouse gases), we could buy decades of time to reduce carbon dioxide emissions.”
Such efforts are underway. Among the most promising are new rules from the U.S. Environmental Protection Agency that will strengthen reporting requirements on emissions from oil and natural gas facilities in hopes of reducing methane and other pollutants.
Last year, California passed groundbreaking legislation that will require large U.S.-based companies doing business in the state to disclose their annual greenhouse gas emissions starting in 2026, the first such rule in the country.
State bills aimed at plugging orphan oil wells and setting methane emissions targets for dairy and cattle producers It could also make a difference, as could efforts to electrify homes and buildings, said Jackson, who recently wrote a Book on the transition to clean energy.
But these efforts can’t obscure the fact that emissions continue to accelerate dangerously. A 2021 global pledge on methane signed by 158 countries, including the United States, aims to reduce global methane emissions by at least 30% from 2020 levels by 2030, but “it hasn’t really started to happen yet,” Jackson said.
“There are still no greenhouse gases dispersing into the atmosphere, and in the case of gases like methane, levels are rising faster than before,” he said. “This cannot continue on a habitable planet. We seem to be heading towards 3 degrees Celsius, which is a terrifying prospect and I hope it is a mistake.”
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