Human activity is responsible for two-thirds of global methane emissions

The world is moving in a perilous direction when it comes to global warming methane emissions, which are reaching record levels, largely due to human activity, a new study warns.

Although many people associate methane with cow burps and thawing permafrost, a paper published this week in the journal Earth System Science Data found that global methane emissions over the past five years have grown faster than ever before — and at least two-thirds of those emissions now come 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 from the previous year.

Experts say the findings are extremely worrying because they highlight that the planet is on the verge of surpassing the desired limit of 2.7 degrees of warming compared to pre-industrial times – an international benchmark often cited as 1.5 degrees Celsius. In fact, methane contributed to nearly a degree of global warming in the 2010s.

“In terms of the methane contribution, we’re on a trajectory that’s about 3 degrees Celsius right now,” said Rob Jackson, the study’s lead author, who is also a climate scientist at Stanford and president of the Global Carbon Project. “We’re nowhere near 1.5 or even 2 degrees Celsius if you look at methane alone.”

The 3-degree Celsius (about 5.4 degrees Fahrenheit) scenario would have potentially disastrous consequences, including rapid melting of ice caps, prolonged heat waves and droughts, water shortages, famines, and political and social unrest, among other consequences outlined by the Intergovernmental Panel on Climate Change.

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But even though methane has a warming effect 30 to 80 times stronger than CO2, ton for ton, it has one advantage: its lifetime is relatively short. Methane stays in the atmosphere for about a decade, while CO2 lasts hundreds of years or much longer.

“This is really the only lever we have to slow global warming over the next decade or two,” Jackson said. “We can’t really do anything about the billions of tons of carbon dioxide in the air right now, but for methane, we could see concentrations return to pre-industrial levels within a decade if we could magically stop anthropogenic emissions.”

“It’s not going to happen soon,” he added, “but that should be our goal. It would give us at least half a degree of gain.” [Celsius] of reducing global warming.

Sources of methane emissions can be divided into two broad categories: human sources, which come primarily from agriculture, fossil fuels, landfills and waste; and natural sources such as wetlands, peatlands and marshes that release methane when bacteria break down their organic matter.

The study finds that emissions from both categories are increasing, although human sources appear to be generating an increasingly large 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 growing concern about methane emissions from natural systems.

Uprising global temperatures Microbial activity is increasing in warm tropical areas such as the Congo, the Amazon and Southeast Asia, releasing more methane that could in turn contribute to greater warming in a worrying feedback loop, Jackson said.

“The fact that everything is still going up is disconcerting. But what worries me most is the risk of increasing natural emissions, particularly in tropical regions,” he said. “We think we’re starting to see it, but we’ll really know for sure in four or five years – and it would be very bad news if it started to happen on a large scale.”

Arctic permafrost — once permanently frozen ground — is also thawing amid record global temperatures and the release of carbon and methane into the atmosphere.

Evan Sherwin, a researcher at Lawrence Berkeley Laboratory who was not involved in the study, said its findings were important and comprehensive, although not entirely surprising.

“It’s a pretty stark warning to us – especially given that there have been a lot of efforts to mitigate methane emissions – that the share of methane emissions coming from human sources appears to be increasing,” Sherwin said.

He said there is still some uncertainty about the planet’s warming trajectory, particularly because humanity still has a good deal of control over its emissions by the end of the century.

Agriculture is one of many sources of human-made methane. Here, Holstein cows populate a California dairy farm.

(Mel Melcon / Los Angeles Times)

But if methane emissions continue to rise at about the current rate, and CO2 emissions are not reduced as quickly as they should be, warming of 3 degrees Celsius “doesn’t seem out of the question at all to me,” he said.

Like Jackson, he said the potential for increased emissions from natural sources is worrisome and warrants further study, particularly around tropical ecosystems.

He noted, however, that human-caused methane emissions are not increasing everywhere in the world. In Europe, for example, emissions have declined substantially over the past two decades, while Korea, Japan and Australasia have remained roughly stable, the study found. (General calculations for the United States indicate an overall increase over that period.)

“This is a sign that it is possible to keep methane emissions stable or even reduce them quite substantially, which I think is a promising sign,” Sherwin said.

In fact, the finding that humans are now the primary culprit for methane emissions could in some ways be seen as a silver lining in that it is something that can potentially be mitigated or controlled, Sherwin added.

“This is a huge lever that we have to buy time,” he said. “If we take large-scale action to reduce methane emissions – and I should also mention nitric oxide and other short-lived greenhouse gases – we could buy decades to reduce carbon dioxide emissions.”

Such efforts are underway. Among the most promising are new rules from the U.S. Environmental Protection Agency (EPA) that will strengthen reporting requirements for emissions from oil and gas facilities, in hopes of reducing emissions of methane and other pollutants.

Last year, California passed a groundbreaking law that will require large U.S. companies operating in the state to disclose their annual greenhouse gas emissions starting in 2026, the first such rule in the country.

State bills aim to plug orphaned oil wells and set methane emissions targets for dairy producers and livestock farmers could also make a difference, as could efforts to electrify homes and buildings, said Jackson, who recently wrote a book on clean energy transition.

But these efforts can’t obscure the fact that emissions continue to rise dangerously. A 2021 global methane pledge signed by 158 countries, including the United States, aims to reduce global methane emissions by at least 30% below 2020 levels by 2030, but “hasn’t even really begun to materialize yet,” Jackson said.

“There is no decline in greenhouse gases in the atmosphere yet, and for gases like methane, levels are rising faster than ever before,” he said. “This cannot continue on a habitable planet. It looks like we are heading towards 3 degrees Celsius, which is a terrifying prospect, and I hope it is wrong.”