A new study warns that the world is heading in a dangerous direction as global warming methane emissions have soared to record highs, driven largely by human activities.
When we think of methane, we often think of air and water vapor, but a study published in the journal Nature this week found that global methane emissions have increased faster than ever over the past five years, and that at least two-thirds of those emissions are man-made.
In April of this year, methane levels reached 1,931 ppb, up 11 ppb from the previous year.
Experts said the findings were extremely worrying because they showed that the planet is on track to rise far beyond the desired limit of 2.7 degrees Celsius above pre-industrial levels, an international standard often referred to as the “maximum limit.” In fact, methane contributed almost 1 degree to global warming in the 2010s.
“In terms of the methane contribution, we’re currently on a trajectory consistent with about 3°C of warming,” said Rob Jackson, lead author of the study, a climate scientist at Stanford University and chair of the EPA. “If you look at just methane, we’re nowhere near 1.5°C or 2°C.”
A 3 degree Celsius (about 5.4 degrees Fahrenheit) warming scenario, as outlined by the Intergovernmental Panel on Climate Change, would result in potentially disastrous consequences, including rapid melting of ice sheets, prolonged heat waves and droughts, water shortages, famine, and political and social unrest.
But although methane is 30 to 80 times more warming than carbon dioxide per ton, it has one advantage: it is relatively short-lived: Methane lasts in the atmosphere for only about 10 years, while carbon dioxide can last for hundreds of years or even longer.
“This is the only thing we can do to slow warming over the next decade or two,” Jackson said. “There’s nothing we can do right now about the trillion tonnes of carbon dioxide in the atmosphere, but with methane, if we could pull a magic wand and stop human emissions, concentrations could return to pre-industrial levels within a decade.”
“That’s unlikely to happen anytime soon,” he added, “but that should be our goal, and it would help limit warming by at least half a degree (Celsius).”
Methane emissions can be broadly divided into two categories: anthropogenic sources, which come mainly from agriculture, fossil fuels, landfills and waste, and natural sources such as wetlands, marshes and swamps, where methane is released as bacteria break down organic matter.
The paper found that emissions from both categories are increasing, but that anthropogenic sources appear to be contributing an increasingly larger share, now accounting for about 65% of estimated emissions, compared with 60% in 2020, Jackson said. (The actual share could 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.
Jackson said increased microbial activity in tropical hotspots such as the Congo, the Amazon and Southeast Asia is causing more methane to be released, setting off a worrying feedback loop that further accelerates warming.
“The fact that everything is still increasing is disturbing, but what concerns me most is the possibility of increased natural emissions, especially in the tropics,” he said. “I think we’re starting to see it, but it’s going to take another four or five years before we really know. And if it starts happening on a large scale, then that’s really bad news.”
Arctic permafrost, or soil that was once permanently frozen, also releases carbon and methane into the atmosphere.
Evan Sherwin, a research scientist at Lawrence Berkeley Laboratory who was not involved in the study, said the findings are important and comprehensive, but not entirely surprising.
“Given that there have been many efforts to mitigate methane emissions, it’s a very stark warning to us that the proportion of methane emissions attributable to anthropogenic activities appears to be increasing,” Sherwin said.
When it comes to global warming, he said there’s still a lot of uncertainty about what trajectory the Earth is on, especially because humanity still has a lot of control over emissions between now and the end of the century.
But he said a 3°C warming was “not at all improbable to me” if methane emissions continued to grow at roughly the current rate and carbon dioxide emissions were not cut as quickly as needed.
Like Jackson, he said the possibility of increased emissions from natural sources is a concern and requires further study, especially when it comes to tropical ecosystems.
But they noted that man-made methane emissions are not increasing everywhere in the world. For example, the study found that emissions in Europe have fallen significantly over the past two decades, while they’ve remained roughly steady in South Korea, Japan and Australia. (Rough estimates for the United States show an overall increase over that period.)
“I think this is a promising sign that it’s possible to hold methane emissions constant or even reduce them quite substantially,” Sherwin said.
In fact, the finding that humans are currently the primary driver of methane emissions could in some ways be seen as a ray of hope, in that they may be able to be mitigated or controlled, Sherwin added.
“This is a huge step to buy us time,” he said. “If we make a massive effort to reduce methane emissions, and also nitrous oxide and other short-lived greenhouse gases, it will buy us decades of time to reduce our carbon emissions.”
Such efforts are underway, the most promising being new rules from the US Environmental Protection Agency regulating oil and gas facilities in hopes of reducing methane and other pollutants.
California passed a landmark bill last year requiring large U.S.-based companies doing business in the state to make the transition starting in 2026, the first such rule in the nation.
State bills setting targets for methane emissions could also help, said Jackson, who wrote the recent paper, as could efforts to electrify homes and buildings.
But these efforts don’t negate the fact that emissions continue to accelerate in a dangerous way. An agreement signed in 2021 by 158 countries, including the U.S., aims to reduce global methane emissions by at least 30% by 2030 compared to 2020 levels, but “we haven’t even started to get going yet,” Jackson said.
“Greenhouse gases in the atmosphere have not yet decreased, and levels of gases such as methane are rising more rapidly than before,” he said. “This cannot continue on a habitable planet. We appear to be heading for a 3°C increase in temperature, which is a frightening prospect and one I hope is wrong.”
