Why methane surged in the early 2020s—and what it reveals

The atmosphere's ability to clean itself weakened just as wetlands got wetter. That convergence sent methane levels climbing at a pace scientists hadn't seen before.

Between 2019 and 2023, atmospheric methane jumped by 55 parts per billion, hitting a record 1,921 ppb in 2023. The sharpest spike came in 2021, when levels rose nearly 18 ppb in a single year—84 percent faster than the year before. An international team publishing in Science this week has finally pinned down why.

The Atmosphere Lost Its Cleaner

Methane doesn't just hang around forever. Hydroxyl radicals—invisible molecules drifting through the air—break it down. But during 2020–2021, those radicals became scarce. Their decline accounts for roughly 80 percent of why methane accumulated so quickly.

The culprit was partly human. COVID-19 lockdowns cut nitrogen oxide pollution, and fewer nitrogen oxides meant fewer hydroxyl radicals got produced. At the same time, a prolonged La Niña event from 2020 to 2023 flooded tropical regions with rain. Wetlands expanded. Rivers swelled. Lakes deepened. And in all that water, microbes thrived—the kind that belch methane.

Hanqin Tian, an Earth scientist at Boston College who led much of the research, puts it plainly: "As the planet becomes warmer and wetter, methane emissions from wetlands, inland waters, and paddy rice systems will increasingly shape near-term climate change."

Managed Land Matters More Than We Thought

The surge wasn't just natural systems responding to weather. Paddy rice fields in Southeast Asia and tropical Africa ramped up emissions significantly. Inland waters—reservoirs, rivers, lakes—that humans have modified also contributed more than previous models predicted. Arctic wetlands, warmed by rising temperatures, released more methane as microbial activity accelerated.

South America tells a different story. In 2023, an extreme El Niño drought dried out wetlands there, and methane emissions fell. The lesson is stark: methane emissions are exquisitely sensitive to climate extremes. What happens in one region depends entirely on whether it's wet or dry that year.

What Wasn't Driving It

Here's what's notable by its absence: fossil fuels and wildfires barely moved the needle. Chemical fingerprinting—a technique that identifies the source of methane molecules—shows that microbial sources in wetlands, waters, and agriculture account for nearly all the recent surge. That's important context. It means the 2020s methane spike wasn't about coal mines or oil wells working overtime. It was about the planet's water systems responding to climate shifts.

Philippe Ciais, the study's lead author at the University of Versailles Saint-Quentin-en-Yvelines, sees the bigger picture: "Future methane trends will depend not only on emission controls, but on climate-driven changes in natural and managed methane sources." In other words, even if we cap fossil fuel emissions tomorrow, methane from warming wetlands will keep rising unless we also slow climate change itself.

The research reveals gaps in how we monitor the planet. Current models underestimated how much methane comes from flooded ecosystems. Better tracking of wetlands and inland waters—especially as they expand and contract with climate patterns—will be essential for predicting what comes next.