Removing methane from the atmosphere could significantly slow temperature increase

Taking methane out of the atmosphere could be a game changer in the fight against global warming, scientists told a European Commission sponsored side event at COP26 in Glasgow.

As one of the chief global warming culprits, methane is responsible for at least a quarter of the current global warming. There is less of this gas out in the atmosphere than carbon dioxide, but it is around 80 times more potent in trapping heat in the atmosphere than CO2 over a 20 year period. And emissions are on the rise, with last year recording the biggest increase in at least 40 years.

More than half of methane comes from human activities, such as agriculture, landfills and the production of natural gas, coal and oil. Reducing methane emissions by 30%, a goal world leaders are setting for 2030, could reduce global warming by 0.2 degrees Celsius

Limiting methane leaks during the extraction of oil and gas and improving management of landfill sites could significantly reduce how much gas escapes into the atmosphere.

“If we implement all technologies that we know of today to reduce global methane emissions from human activities, we may achieve 30 to 45% reductions in 2030 and just over 50% in 2050,” said Lena Höglund-Isaksson, senior research scholar at the International Institute for Applied Systems Analysis in Austria.  

The next step is actively removing it. But this is difficult and many argue not worth the effort, since methane only stays around in the atmosphere for only 10 to 12 years.

One method to directly remove methane would involve releasing sea water aerosols fortified with iron into the atmosphere, mimicking one of the two ways in which methane is naturally removed from the atmosphere. The major route is via oxidation with hydroxyl radicals, but for around 2% of methane, oxidation happens when the gas interacts with chlorine in sea spray, a reaction that is catalysed by sunlight.

This natural process is much faster than oxidation of methane with hydroxyl radicals and scientists are now looking at how to enhance it. “In a lab, we are seeing that if we add a little bit of iron to a sea salt aerosol, it gains a superpower. It becomes 10 to 100 times as strong,” said Maaten van Herpen, science adviser at Methane Action.

Policing global pledges

Methane is at the centre of the COP26 UN climate summit. Today, the leaders of over 100 countries are set to launch the Global Methane Pledge, a US and EU-led effort to slash methane emissions by 30% compared with 2020 levels by 2030.

The US is expected to announce measures for cutting 41 million tons of methane emissions between 2023 to 2035.

These efforts will be monitored by a new methane observatory tracking emissions around the world, which was launched on Sunday at the G20 meeting, with a budget of €100 million over the next five years.

The observatory’s first focus will be the fossil fuel sector, which is responsible for 30% of man-made emissions, but it is expected to eventually expand to agriculture, waste and other sectors.

“Existing systems do not allow us to determine precisely enough where these emissions happen across the globe and in what volumes. Once better data is available, countries can take swift and well-targeted action,” said EU Commissioner for Energy, Kadri Simson.

But cutting emissions may not be enough, as the tipping point for irreversible climate warming approaches. “The pledge is a good beginning, but it’s only that,” said Durwood Zaelke, president of the Washington-based Institute for Governance and Sustainable Development.

There are questions as to what contribution direct methane removal can make to reducing global warming: given its limited residence time in the atmosphere, slashing emissions could be enough to reduce pollution in the next 20 years.

Most methods of methane removal involve moving air over a catalyst to breakdown methane faster, but none of the technologies are mature yet and would require significant investment.

But Jackson says steady levels of reduction are not a given. For example, natural sources of methane such as wetlands may start releasing more of the gas as the planet warms. “We need methane removal to be ready for these eventualities,” said Jackson.

Zaelke stressed the importance of acting fast, highlighting that pulling methane out of the atmosphere is key to accelerating the process. “When you understand the need for speed, you understand how important cutting methane is and learning how to pull it out of the atmosphere. Indeed, this may be the single most important strategy to keep us from losing control of the climate system,” he said.