February 3, 2023

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The murky origins of an ominous methane wave

That is, because we polluted the environment less—heavy industry shut down, flights were canceled, people stopped commuting—we also produced fewer pollutants that normally break down methane. There’s a second unfortunate and surprising consequence of reducing pollution: burning fossil fuels also creates aerosols, which throw some of the sun’s energy back into space and cool the climate somewhat. While it’s imperative that we decarbonize as quickly as possible, turning off the beneficial effects of NOx and aerosols has some unintended – and twisted – side effects.

“Burning fewer fossil fuels will result in there being fewer OH radicals in the atmosphere, which will lead to increases in methane concentrations,” says geoscientist George Allen of Virginia Polytechnic Institute and State University, who agreed to provide an accompanying comment authored the paper, but was not involved in the research. “So that will reduce the effectiveness of measures to combat global warming.”

This makes it all the more urgent for humanity to take drastic steps to reduce both methane and CO2 emissions, especially given the alarming deterioration in northern countries as the planet warms. The increase in emissions from nature also adds more urgency to the fight to conserve these lands. For example, humans drain swampy peatlands and burn them to convert them to cropland, turning them from carbon sinks to carbon sources. And because the Arctic is warming more than four times faster than the rest of the planet, human development can push further north, kicking up soil-secured carbon as people build roads and homes. All of this only exacerbates the problem.

This type of mining blurs the line between human and natural sources of methane. “While some sectors are clearly anthropogenic – industry, transport, landfills and waste – other ‘natural’ sectors such as polluted waterways and wetlands can be impacted by humans to a small, medium or high degree, which in turn can increase ‘natural’ methane emissions”, says Judith Rosentreter, a senior research fellow at Southern Cross University, who studies methane emissions but was not involved in the new research.

Meanwhile, the Arctic region is turning green with new vegetation darkening the landscape and further warming the ground. Permafrost — which covers 25 percent of the northern hemisphere’s land surface — is thawing so fast it’s ripping holes in the earth, known as thermokarsts, that fill with water and provide the ideal conditions for methane-spitting microbes.

“A lot of organic carbon is trapped there – it’s like a frozen compost heap in your own garden,” says Torsten Sachs from the GFZ German Research Center for Geosciences, who was not involved in the new research. “There’s a lot of talk and a lot of speculation and a lot of modeling about how much greenhouse gases will come out of these thawing and warming permafrost areas. But unless you have real data on the ground, you can’t really prove that.”

Sachs did just that, venturing into the Siberian tundra for months to collect data. In a recent article published in Nature Climate Change, he found that methane production has increased by 2 percent per year every June and July since 2004. Interestingly, this does not appear to be the case, although this corresponds to significantly higher atmospheric temperatures in the region corresponding to permafrost thawing. Instead, the extra methane can come from wetlands that sit on top of permafrost.

This is the extreme complexity that scientists are trying to better understand. While the new paper’s modeling can tear apart the methane emitted by humans and nature, on-site data is also needed to fully understand the dynamics. The ultimate concern is that runaway carbon emissions could trigger climate feedback loops: we’re burning fossil fuels, warming the planet, thawing permafrost and forming larger methane-yielding wetlands. This will have serious consequences for the rest of the planet.

However, the scientists cannot yet say whether we are already witnessing a feedback loop. This new study focused on 2020, so researchers need to collect methane data over years and pinpoint the source of these emissions. But methane emissions were even higher in 2021. “The notion that warming feeds warming is definitely something to worry about,” says James France, senior international methane scientist at the Environmental Defense Fund. “It’s very difficult to defuse. So it really reinforces the idea that we need to double down and really focus on mitigation in the areas that we can control.”