When Human Activity Dropped During Covid-19, Methane Levels Surprisingly Spiked. Now, a Study Points to Two Reasons Why

In a paradox of air pollution, a decrease in man-made pollutants led to more methane in our atmosphere. And natural wetlands released more of the planet-warming gas at the same time

As the world shuttered in 2020 amid Covid-19 lockdowns, scientists expected to see one silver lining to the pandemic: a decrease in air pollution. With fewer cars on the roads and a drop in industrial activity, researchers did notice a dip in daily carbon dioxide emissions and other pollutants. But methane, the second-largest contributor to climate change, surprisingly surged to its highest levels in the atmosphere since researchers began measuring it in the 1980s.

Six years later, a team of more than 40 scientists has offered an answer to this chemical mystery in a study published last week in Science, pointing to dynamics in the atmosphere and natural areas.

“By providing the most up-to-date global methane budget through 2023, this research clarifies why methane rose so rapidly—and why it has recently slowed,” says Philippe Ciais, a researcher at France’s Laboratory for Climate and Environmental Sciences (LSCE) and lead author of the paper, in a statement from the European Space Agency.

When methane enters the atmosphere, it interacts with a molecule called the hydroxyl radical, which destroys the methane by converting it into less harmful gases. Hydroxyl radicals, though, have a very short lifespan and must be constantly replaced.

To create hydroxyl radicals, you need reactions between sunlight and various gases—including air pollutants emitted from manmade processes, such as nitrogen oxides. When less air pollution entered the atmosphere due to the 2020 lockdowns, it meant fewer hydroxyl radicals were being created, and they could not destroy as much methane.

This air pollution paradox—where less emissions of one pollutant meant that another remains in the atmosphere for longer—suggests that researchers must prioritize more nuanced tracking of atmospheric processes, says Clement Albergel in the statement. Albergel is head of the ESA’s Actionable Climate Information section and was not involved in the research.

“The study underscores the growing importance of satellites—not only for tracking greenhouse gases, but for revealing the subtle chemical processes that govern their fate in the atmosphere,” Albergel adds. “It shows that climate surprises are not always about what we emit, but about how the atmosphere responds.”

Around 80 percent of the methane surge was a result of this pollutant reaction, the authors predict. But the rest primarily came from an increase in methane emissions, the work suggests, rather than a decrease in the atmosphere’s ability to destroy them.

Though manmade methane emissions dropped during the pandemic, methane is also released by natural sources, including wetlands. The pandemic coincided with La Niña, a periodic climate event that causes increased rainfall in tropical areas. As regions throughout Africa and Southeast Asia got wetter, they became more ideal environments for methane-producing microbes.

“As the planet becomes warmer and wetter, methane emissions from wetlands, inland waters and paddy rice systems will increasingly shape near-term climate change,” Hanqin Tian, an environmental scientist at Boston College and a co-author of the study, says in a statement from Boston College.

Both the increased natural production and the decreased natural destruction of methane described in the study are largely outside of human control, but the researchers urge a reduction in manmade emissions to offset these natural processes.

“For me, this means we need to improve air quality and, even more importantly, mitigate greenhouse gas emissions, to offset these negative effects linked to the chemical-climate relationship,” says Marielle Saunois, a researcher at LSCE and a co-author of the study, to the Agence France-Presse’s Julien Mivielle and Laurent Thomet.

Around 160 countries are part of the Global Methane Pledge, an initiative launched in 2021 to cut methane emissions by 30 percent by 2030. Though methane is second to carbon dioxide in its contributions to climate change and has a shorter lifespan in the atmosphere, it has a more potent warming effect.

To explain the methane surge and create a “global methane budget,” which tracks the amount of methane added and removed from the atmosphere, the researchers brought together observations from the National Oceanic and Atmospheric Administration, data from the GOSAT satellite and various computer models.

“This paper really highlights the success of all these multitiered methods that we’ve developed as a community,” says Francesca Hopkins, a climate change scientist at University of California, Riverside, who was not involved in the work, to Fionna Samuels at Chemical and Engineering News. She adds that “the whole globe relies on these datasets.”

Editor’s Note, February 12, 2026: The headline of this article has been changed to clarify that overall methane levels in the atmosphere increased.