Human activity now drives two-thirds of global methane emissions, the report says

The world is headed in a dangerous direction with planet-warming methane emissions rising to record highs caused largely by human activity, new research warns.

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

In April of this year, methane concentrations reached a record 1,931 ppb – an increase of 11 ppb compared to the previous year.

Experts said the findings were deeply troubling because they set the planet on course to blow well beyond the required 2.7 degrees of warming in the pre-industrial era – an international benchmark often quoted as 1.5 degrees Celsius. In fact, methane contributed to nearly one degree of global warming in 2010.

“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 Stanford climate scientist and chair of the Global Carbon Project. “We’re a long way from 1.5 or even 2 degrees C if you just look at methane.”

A 3 degrees Celsius – roughly 5.4 degrees Fahrenheit – scenario would have potentially catastrophic consequences, including rapid melting of ice sheets, prolonged heat and drought, water scarcity, famine and political and social unrest, among other outcomes outlined by the Intergovernmental Panel on Climate Change.

But while methane is 30 to 80 times more potent at warming than CO2, ton for ton, it has one advantage: It’s also relatively short-lived. Methane lasts about ten years in the atmosphere compared to 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. “There’s really nothing we can do about the trillions of tons of carbon dioxide in the air right now on this time frame, but for methane we could see concentrations return to pre-industrial levels within a decade if we could stop anthropogenic emissions with a magic wand.”

“That’s not likely in the foreseeable future,” he added, “but that should be our goal. That would allow us to reduce warming by at least half a degree (Celsius).

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

The paper found that emissions from both categories are rising, although human sources appear to be generating an increasing share, now accounting for about 65% of estimated emissions, compared with 60% in 2020, Jackson said. (The actual share may be even higher depending on how some sources are classified, such as emissions from dams and reservoirs.)

However, there is also growing concern about methane emissions from natural systems.

Uprising global temperatures they increase microbial activity in tropical hot spots like the Congo, the Amazon and Southeast Asia, which release more methane, which in turn could contribute to more warming in a worrisome feedback loop, Jackson said.

“The fact that everything keeps increasing is worrying. But the most interesting part for me is the potential for increased natural emissions, especially in the tropics,” he said. “We think we’re starting to see it, but we really won’t know for sure for another four or five years – and that’s really bad news if it starts to happen on a large scale.”

Arctic permafrost – or ground that was once permanently frozen – is also melting amid record high global temperatures, releasing carbon and methane into the atmosphere.

Evan Sherwin, a scientist at Lawrence Berkeley Laboratory who was not involved in the study, said its findings are important and complex, though not entirely surprising.

“It’s a pretty stark warning to us — especially given that so much effort has gone into mitigating methane emissions — that the proportion of methane emissions that come from human-caused sources appears to be increasing,” Sherwin said.

He said there is still a significant degree of uncertainty about what trajectory the planet is on in terms of warming, especially since humanity still has considerable control over its emissions between now and the end of the century.

But if methane emissions continue to rise at roughly the current rate and CO2 emissions don’t fall as fast as needed, 3 degrees Celsius warming “doesn’t seem out of the question to me,” he said.

Like Jackson, he said the potential for increased emissions from natural sources is concerning and warrants further study, particularly as it relates to tropical ecosystems.

However, he noted that methane emissions from human sources are not increasing everywhere in the world. In Europe, for example, emissions have fallen significantly over the past two decades, while Korea, Japan and Australasia have remained roughly the same, the study shows. (Broad calculations for the United States suggest an overall increase over that time frame.)

“That’s an indication that it’s possible to keep methane emissions stable, or even reduce emissions significantly, which I think is a promising sign,” Sherwin said.

In fact, finding that humans are now a major driver of methane emissions could be seen as a silver lining in some ways, in that it’s something that can potentially be mitigated or controlled, Sherwin added.

“It’s a huge lever we have to buy time,” he said. “If we make a big effort to reduce methane emissions — and I should say 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 U.S. Environmental Protection Agency rules that will strengthen emissions reporting requirements from oil and gas production facilities in hopes of reducing methane and other pollutants.

Last year, California passed groundbreaking legislation that will require major U.S. companies doing business in the state to disclose their annual greenhouse gas emissions starting in 2026, the first such rule in the country.

State laws aimed at plugging orphaned oil wells and setting targets for methane emissions dairy and livestock producers it could also make a difference, as can efforts to electrify homes and buildings, said Jackson, who recently wrote a a book on the clean energy transition.

But such efforts cannot deny the fact that emissions continue to accelerate dangerously. The 2021 Global Methane Pledge, signed by 158 countries, including the U.S., aims to reduce global methane emissions by at least 30% from 2020 levels by 2030, but “it hasn’t really started yet,” Jackson said.

“No greenhouse gases are decreasing in the atmosphere yet, and for gases like methane, levels are increasing faster than before,” he said. “This cannot continue on a habitable planet. It looks like we’re heading for 3 degrees C, which is a scary prospect, and I hope it’s wrong.”