The dark origins of a disturbing methane surge

That is, as we’ve polluted less – heavy industry has stopped, flights have been cancelled, people have stopped commuting – we’ve also produced less of the pollutant that normally breaks down methane . This is a second unfortunate and surprising consequence of the reduction in pollution: the combustion of fossil fuels also produces aerosols which send some of the solar energy back into space, a little cool the climate. If it is imperative to decarbonize as quickly as possible, removing the beneficial effects of NO_X and aerosols have unintended, twisted side effects.

“Burning fewer fossil fuels will lead to fewer OH radicals in the atmosphere, which will lead to increased methane concentrations,” says Earth scientist George Allen of the Polytechnic Institute of Virginia and the University of State, who wrote an accompanying commentary on the article but was not involved in the research. “This will therefore reduce the effectiveness of measures to combat global warming.”

This makes it all the more urgent for humanity to take drastic action to reduce both methane and CO₂ emissions, especially given the alarming degradation of northern lands as the planet warms. The growth of emissions from nature also makes the fight against preserve these lands. People are, for example, drain soggy bogs and set them on fire to convert them into agricultural land, which turns 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 encroach farther north, accumulating carbon sequestered in the ground as people build roads and homes. All of this only makes the problem worse.

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

Meanwhile, the Arctic region is greening, thanks to new vegetation, which darkens the landscape and further warms the ground. Permafrost — which covers 25 percent of the earth’s surface in the northern hemisphere – thaws so quickly that it is dig holes in the groundknown as thermokarst, which fill with water and provide the perfect conditions for methane belching microbes.

“There’s a lot of organic carbon locked in there, it’s like a frozen compost heap in your own garden,” says Torsten Sachs of the German GFZ Research Center for Geosciences, who was not involved in the news. research. “There is a lot of discussion, speculation and modeling about how much greenhouse gas will come out of these thawing and warming permafrost zones. But until you have real data in the field, you can’t really prove it.

Sachs did just that, venturing into the Siberian tundra for months to collect data. In a paper he recently published in Natural climate change, he found that methane production in June and July increased by 2% per year since 2004. Interestingly, although this corresponds to significantly higher atmospheric temperatures in the region, it does not appear to correspond to permafrost thaw. Instead, the additional methane may come from wetlands above the permafrost.

It is the extreme complexity that scientists are struggling to better understand. While the new paper’s modeling can disentangle the methane emitted by humans and nature, field data is also needed to fully understand the dynamics. The ultimate concern is that runaway carbon emissions could trigger climate feedback loops: we burn fossil fuels, which warms the planet, thaws permafrost, and forms larger methane-emitting wetlands. This will have serious consequences for the rest of the planet.

However, scientists cannot yet say if we are already seeing a feedback loop. This new study focused on 2020, so researchers will need to continue collecting methane data for consecutive years and identify the source of these emissions. But methane emissions were even higher in 2021. “The idea that warming is fueling warming is definitely something to be concerned about,” says James France, senior international methane scientist at the Defense Fund. ‘environment. “It’s very difficult to mitigate. So it really reinforces the idea that we need to redouble our efforts and really focus on mitigation in the areas that we box control.”