COVID lockdowns caused methane surge: Study reveals air pollution paradox

As the world shut down due to COVID, causing less traffic like trains, planes and automobiles, scientists expected the planet to get a break from harmful pollutants like nitrogen dioxide and methane.

But curiously, scientists saw a surge in methane, which is the second-largest contributor to climate warming after carbon dioxide, according to the European Space Agency.

ESA had more than 40 scientists working on why methane surged to the highest level in the atmosphere seen since researchers measuring began in the 1980s.

A study published in Science.org reveals that the surge was actually, albeit accidentally, caused by the lack of pollutants in the air.

“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.

The breakdown of methane occurs when it interacts with the molecule hydroxyl radical, which converts methane into less harmful gases.

To create these radicals, an interaction between sunlight and other gases, like air pollutants created from manmade processes, like nitrogen oxides, occurs, according to Smithsonian Magazine.

But hydroxyl radicals have a short lifespan and thus need to be continually replaced to maintain the constant breaking down of methane.

So while the pandemic shutdown saw canals in Venice turn a beautiful unpolluted blue, it also meant less hydroxyl radicals to break down methane.

Scientists are calling this the air pollution paradox, the phenomenon that fewer emissions of one pollutant can mean another remains in the atmosphere longer. The finding could result in a shift in the way researchers track atmospheric processes.

“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,” ESA member Clement Albergel said. “It shows that climate surprises are not always about what we emit, but about how the atmosphere responds.”

The scientists who authored this study predict that around 80% of the methane surge was due to the lack of hydroxyl radicals, but the other 20% came from a natural increase in methane production.

Methane is released by the breakdown of natural matter in an oxygen-less environment, like deep within wetlands, or in the stomach of ruminants like cattle, sheep, goats and cows.

The pandemic coincided with a La Niña, which brings cooler, wetter weather, which dumped rain on already wet areas in Africa and Asia. As the wetlands take in more rain, they become even more fertile ground for methane production.

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

Researchers suggest humans mitigate greenhouse gas emissions and offset methane production to help balance the chemical-climate relationship.

The Global Methane Pledge is an organization of 150+ countries that are working toward cutting methane emissions by 30% come 2030. It was launched by the EU and the United States in 2021.