After a year of weather extremes, there can no longer be any doubt that the climate is warming rapidly, and no doubt that carbon dioxide is slowly cooking the planet. But the immediate culprit is a different gas altogether: methane.
A potent greenhouse gas, methane is largely responsible for the current rate of warming. It is thus a vital target in the fight to keep global temperature rises below the Paris Agreement’s goal of 1.5°C – as well as offering some of the easiest wins. Yet it has been neglected. “Methane for so long has been a sort of Cinderella gas,” says , University of London. With methane kept below stairs, its ugly sisters carbon dioxide and, to a lesser extent, nitrous oxide (N2O) have got all the attention.
No longer. At the COP26 climate summit in Glasgow, UK, last month, methane finally arrived at the party and won over the assembled dignitaries. World leaders lined up to declare it the belle of the ball, and more than 100 nations signed a pledge to slash its emissions by 2030.
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“Methane has gradually emerged from under CO2‘s shadow and been recognised as a problem”
Depending on how you measure it – which is one of the problems with curbing it – 1 tonne of methane has between 28 and 120 times more warming power than 1 tonne of CO2. However, it stays in the atmosphere relatively briefly – about 12 years – before mostly being converted to CO2, which hangs around for at least a century.
Yet it is present in the atmosphere in tiny quantities – lower even than CO2, which accounted for . Methane is measured in parts per billion, and its current concentration is about , up from 722 in pre-industrial times.
Human-made methane comes from myriad sources that have historically been hard to measure accurately and so have been tough to mitigate. The biggest is agriculture, largely rice paddies and livestock farming, accounting for 40 per cent of emissions. The next biggest, at 35 per cent, is the fossil fuel industry: methane often leaks from oil and gas wells and coal mines. The third biggest source is our waste, mainly landfills and sewage.
Its low concentration and our lack of knowledge – coupled with the fact that, around the turn of the century, methane levels in the atmosphere stopped rising – made the gas seem like “a pretty small player” in climate change, says .
For these reasons, when the world first came together to tackle mounting concentrations of greenhouse gases in the atmosphere, methane was seen as a second-order problem.
The methane mistake
It was included in the basket of six greenhouse gases that the 1997 Kyoto Protocol pledged to reduce. But the protocol – the first worldwide attempt to solve global warming – was really all about CO2. The other five were converted into “CO2 equivalents”: their strength as greenhouse gases was calculated relative to that of CO2 over 100 years. This figure was named “global warming potential 100”, or GWP100.
That turned out to be a mistake. Even though methane was assigned a , this severely underestimated its heating power in the short term. Yes, over the course of a century, 1 tonne of methane warms the planet 28 times as much as a tonne of CO2. But most of that warming happens in the few years after it is emitted. “It was well intentioned to make the problem tractable, but we inadvertently backed ourselves into a corner,” says .
Climate scientists recognised the error and recalculated GWP over 20 years. Methane was originally given a GWP20 of 56, though this has since been raised to 86 – in part to recognise that the , another potent yet short-lived greenhouse gas. But the damage was done. Policy-makers had been handed a hammer marked CO2 and everything else looked like a nail. “Methane just got regarded as a funny sort of CO2,” says Nisbet.
Even GWP20 underestimates the damage done by methane in the very short term. If there were such a thing as GWP1, says Hamburg, methane’s would be a colossal 120. “The challenge we have is that these figures are not wrong, they’re just misleading for policy,” he says.
Even so, in the years since the Kyoto Protocol, methane has gradually emerged from under CO2‘s shadow and been recognised as a problem – and a potential, albeit partial, solution to the climate crisis – in its own right.
One reason for the change of heart is that, for reasons not yet fully understood, the plateau in methane concentrations was temporary and levels are now rapidly rising. In 2000 and 2001, the atmospheric concentration of methane actually fell, but for 18 of the next 19 years, it rose. Last year saw the .
With this rise has come significant warming over and above that caused by CO2. According to Shindell, if you also take ozone into account, the latest report from the Intergovernmental Panel on Climate Change makes it clear that methane is responsible for about half a degree of the 1.2°C of warming so far. “[Curbing] methane is the most important thing we can do for the near term. It’s the only way we can slow down the damages that are mounting,” says Shindell. Hamburg agrees. “Methane is driving the social disruption and the ecological disruption that people are most concerned about,” he says.
Global pledge
The urgency of the methane problem has been common knowledge in climate science circles for about a decade, says Hamburg, but it has now diffused to the policy arena. In the past year, both the United Nations Environment Programme (UNEP) and the International Energy Agency (IEA) have issued . UNEP concluded that deep cuts to human-caused methane emissions were not only possible, but would go a long way to achieving the Paris target.
Cinderella’s true society debut came at COP26, where the presidents of the US and the European Commission formally launched the Global Methane Pledge. At the time of the announcement, more than 80 nations had signed up, agreeing to work collectively to cut global methane emissions by at least 30 per cent from 2020 levels by the end of this decade. And 30 per cent is a minimum. “I think we can probably go beyond that,” said US President Joe Biden at the launch.
What does that mean in terms of global temperatures? A joint .
“40%
Proportion of methane emissions that are due to agriculture”
“30%
Reduction in global methane emissions pledged by more than 100 countries at COP26”
“0.2°
Estimated reduction in the amount of global warming by 2050 due to this pledge”
This saving might sound like small potatoes, but given that all the warming so far amounts to around 1.2°C, about a third of which comes from methane, it isn’t to be sniffed at. And 0.2° is scientifically credible, says Hamburg. That doesn’t mean global temperatures will fall, but it does mean they will rise less quickly than they would have done with business-as-usual methane emissions.
If the pledge is met, the amount of methane-induced warming will be held steady at the current level of between 0.3°C and 0.4°C, says Hamburg. Unlike CO2, methane breaks down quite quickly, so we don’t have to reduce it to zero in order to put its warming effect on hold, he says.
The IEA also did a quick analysis of the pledge, concluding that its impact on warming by 2050 would be equivalent to immediately switching all of today’s cars, trucks, ships and planes to zero-carbon energy. “That is huge,” says .
Not everyone was convinced. A , both in the UK, found that cuts of around 50 per cent were probably needed to shave 0.2° off warming.
Since these analyses, the methane agreement has got bigger. By the end of COP26, there were 109 signatories, collectively responsible for about half of global methane emissions.
There are also heavyweight refuseniks: China, India and Russia, the world’s top three , although China said it “intends to develop a comprehensive and ambitious National Action Plan on methane”.
The pledge has also been criticised for being non-binding and for lacking concrete targets and ways for signatories to account for cuts.
Nonetheless, according to , the pact could be one of the most significant outcomes of COP26.
In part, that is because the pledge is achievable with existing know-how, and at little or no cost. “All the technology to dramatically reduce emissions is in place,” says Hamburg. That mostly consists of stopping leaks from the fossil fuel industry, which the IEA reckons can cut global methane emissions by 25 per cent for free. “Methane is a valuable commodity,” says Shindell. “Many of the controls pay for themselves.”
People often describe this as low-hanging fruit, but Hamburg thinks that fails to capture how easy it is. “There’s a lot of fruit lying on the ground.”
Beyond fossil fuels, the rest can come from other existing technologies, such as capturing methane produced from landfills, periodically draining rice paddies and feeding cows supplements that suppress methane production. A , Shindell and others estimates that if every available methane mitigation technology were thrown at the problem, mid-century warming would be reduced by 0.25°C.
“All the technology to dramatically reduce methane emissions is in place”
Down the road, there are technologies in development, such as direct air capture of methane and methane-lowering treatments for cows, that could take cuts beyond 30 per cent. “We have to be realistic: 100 per cent reduction will probably not be possible,” says Hamburg. “But a 50 per cent reduction should be no problem.”
Two-pronged approach
The problem of measuring methane emissions has also been cracked, says Hamburg. “Methane was lagging. We knew less about where it was coming from and how to measure it. And now it’s leading. You can measure it on the ground, you can do it with drones, aeroplanes, satellites.” He is running a satellite project, , that will monitor emissions from the oil and gas industry and .
Meanwhile, UNEP has set up the . Soon, reckless methane leakers will have nowhere to hide. “Transparency is coming,” says Gould.
The recognition of methane is not just a political breakthrough, but a scientific one too, says Hamburg. “It really represents a major transition to thinking about climate as a two-problem crisis,” he says. “We have the issue of short-lived climate pollutants [principally methane] which really drive the rate of warming in the near term. And then we have CO2, and to a lesser degree N2O, driving the total amount of warming in the longer term. That framing allows us to much more effectively address the crisis. So I think this is a major step forward, where we have two suites of gases and two suites of mitigation solutions.”
Shindell echoes that we need to think of methane and carbon dioxide as separate problems in need of separate solutions. “CO2 takes a long time to respond, so our efforts to decarbonise, while vital for the sake of the long-term future of our planet, really provide very, very little in the way of avoiding climate damages in the near term,” he says. “That makes [methane] a quite distinct player in this game alongside, not instead of, efforts to combat CO2.”
However, we mustn’t see methane reduction as a way of buying time to carry on fiddling while the planet burns. We also have to cut CO2 deeply, right now. “We need to deal with both of them,” says Hamburg. Gould supports this. “You really have to tackle them in parallel,” he says.
The path to 1.5°C
Scientists recognise that shaving 0.2° or more off warming in the short term will still be hugely beneficial. For one thing, it smooths the path to 1.5°C, or wherever we end up once we reach net zero. “We can greatly reduce the rate of warming and have a glide path to wherever we land,” says Hamburg. “If we don’t do it, we end up with a higher rate of warming, and then go down. That’s a much more damaging pathway.”
It could also allow us to limbo dance under some potential tipping points – where things could suddenly get much worse – that lie just beyond warming rising upwards of 1.5°C. “If we want to really lower the likelihood of multiple tipping points, we really have to hold the line at 1.5°C of warming,” says , UK. “The fundamental point is that if we can rapidly decrease methane emissions, that could really make a difference.”
This, however, is still a big if. The methane pledge, if it is enacted, can create a much-needed firebreak in the escalating climate crisis. But it may yet turn into a pumpkin. What really counts are legally binding commitments, and on methane, these are still as rare and fragile as a glass slipper. The Glasgow Climate Pact agreed at COP26 does mention methane, but only once and quite feebly: it “Invites Parties to consider further actions to reduce by 2030 non-carbon dioxide greenhouse gas emissions, including methane.”
“I’m dismayed,” says Nisbet. “This is a very weak way to respond to the urgency of acting on methane.”
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