The atmosphere's ability to clean itself temporarily broke down just when it mattered most. Between 2020 and 2021, levels of hydroxyl radicals—the invisible chemical scrubbers that break down methane in the air—plummeted. This wasn't because emissions suddenly exploded. It was because the air lost its capacity to handle them.
An international research team, led by Boston College's Hanqin Tian, has traced what happened. Their findings, published in Science, reveal a perfect storm of two separate problems colliding at once: a weakened atmosphere and a wetter-than-usual world.
The Cleanup Crew Went Missing
Hydroxyl radicals are what keeps methane in check. They're the atmosphere's primary methane destroyer, constantly breaking down the gas before it can trap heat. During 2020-2021, these radicals declined sharply—accounting for roughly 80 percent of why methane accumulated so rapidly during those years.
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Start Your News DetoxThe culprit was partly the pandemic itself. When lockdowns reduced nitrogen oxide pollution from vehicles and industry, those emissions normally help generate hydroxyl radicals. With fewer of them being produced, the atmosphere's cleaning power weakened precisely when global methane emissions were rising.
At the same time, a prolonged La Niña weather pattern from 2020 to 2023 drenched tropical regions with above-average rainfall. Flooded landscapes—wetlands, rivers, lakes, paddy fields—are where methane thrives. Microbes in waterlogged soil produce the gas as they decompose organic matter. More water meant more of these ideal breeding grounds.
The result was a spike in emissions from some of the world's most productive ecosystems. Tropical Africa and Southeast Asia saw the largest increases, while Arctic wetlands also ramped up production as warmer temperatures accelerated microbial activity. The exception was South America: an extreme El Niño-driven drought in 2023 actually suppressed methane emissions there, showing just how tightly methane release is tied to rainfall patterns.
The Hidden Emitters
What surprised researchers was how much of this methane came from managed systems—rice paddies, reservoirs, and inland waterways—rather than pristine nature. These sources are often underrepresented in global climate models, meaning scientists have been underestimating how much methane agriculture and water management release. Tian's team, using advanced Earth system models that link land, freshwater, and atmospheric processes, finally made these connections visible.
Fossil fuels and wildfires played a minor role in the recent spike. Chemical fingerprinting showed that microbial sources—wetlands, inland waters, and agriculture—drove nearly all of the observed increase.
The broader picture is both clarifying and unsettling. The methane surge wasn't driven by a sudden explosion of industrial emissions. It was driven by natural systems responding to climate conditions, amplified by a temporary breakdown in the atmosphere's ability to clean itself. As the world continues warming, wetlands will only expand and become more active. The question now is whether we can improve our models enough to predict these shifts before they happen.
