When COVID-19 lockdowns cleared city skies and quieted highways in 2020, most people assumed greenhouse gas concentrations would follow suit. Methane did the opposite. The annual increase in atmospheric methane nearly doubled compared to the prior year, and a growing body of research now pins the blame on two factors that had little to do with fossil fuel leaks or agriculture: swelling wetland emissions and a crippled atmospheric cleaning mechanism that normally breaks methane down.
The Numbers Behind the Methane Spike
The scale of the 2020 anomaly is hard to overstate. According to long-running NOAA measurements, the globally averaged annual methane increase jumped from roughly 9.63 parts per billion (ppb) in 2019 to about 14.78 ppb in 2020. That alone would have been striking, but the acceleration continued: the 2021 figure climbed to approximately 17.71 ppb, the largest single-year rise in NOAA’s records, which stretch back to the 1980s. These are not modeled estimates. They come from a global network of surface flask measurements that serves as the ground truth for atmospheric methane tracking.
What makes the spike so counterintuitive is context. Industrial output fell, road traffic plummeted, and oil and gas operations slowed during lockdowns. Anthropogenic methane emissions likely declined during this period, according to a detailed Nature analysis that reconstructed emissions and atmospheric chemistry during the early pandemic. If human sources were shrinking, something else had to be pushing concentrations up. That tension between falling human emissions and rising atmospheric methane is the central puzzle researchers set out to solve, and it forced them to look beyond the usual suspects in the fossil fuel and agricultural sectors.
Wetlands Turned Up the Faucet
The first of the two identified drivers is natural: wetland emissions. Waterlogged soils and flooded ecosystems are the planet’s largest natural source of methane, because microbes in oxygen-poor sediments produce the gas as they decompose organic matter. Wetter-than-average conditions in key tropical and boreal wetland regions during 2020 appear to have amplified this process. A team working with the European Space Agency’s climate program reported that expanded inundation in major basins, combined with warmer temperatures, led to substantially higher methane output from sensitive wetland regions that were already known hotspots.
This matters for anyone tracking climate policy because wetland methane is largely beyond direct human control. Warming temperatures and shifting rainfall patterns can expand saturated soils, and those expansions feed back into more methane, which drives more warming. Early analyses of the 2020 spike tended to focus on fossil fuel infrastructure as the likely culprit, a framing that may have delayed recognition of how much natural systems were contributing. If current climate models undercount wetland sensitivity to precipitation changes, as some researchers now suggest, then methane budgets could be systematically underestimating future risk from these ecosystems, especially in a world where extreme rainfall events are becoming more common.
The Atmosphere Lost Its Cleaning Crew
The second driver is more surprising and more directly tied to the pandemic. Hydroxyl radicals, often abbreviated as OH, function as the atmosphere’s primary oxidizing agent. They react with methane and break it down, acting as a chemical sink that limits how long the gas persists. OH production depends heavily on nitrogen oxides, or NOx, which are released by vehicle exhaust, power plants, and industrial combustion. When lockdowns slashed NOx emissions worldwide, OH concentrations fell in tandem. The result: methane that would normally have been destroyed lingered in the atmosphere far longer than usual, effectively lengthening its atmospheric lifetime during the early 2020s.
Researchers at NASA emphasized this chemical chain in a recent Earth Observatory overview, describing how reduced NOx altered the balance of oxidants and weakened the methane sink. ESA scientists reached similar conclusions, noting that the lockdown-driven drop in combustion-related gases triggered a measurable decline in hydroxyl that would normally destroy methane. Think of it as turning off a drain while the faucet stays on. Even though human methane emissions probably shrank, the reduced capacity to remove methane from the air more than offset that decline, turning a modest emissions dip into a net concentration surge.
Why Early Explanations Missed the Mark
In the months after the spike became apparent, much of the public discussion centered on fossil fuel leaks and agricultural sources. Those are legitimate long-term drivers of methane growth, but they could not explain why the increase accelerated precisely when industrial activity was contracting. The Nature study’s detailed reconstruction of emissions and sinks showed that the growth-rate anomaly was consistent with a combination of weakened OH and boosted wetlands, rather than a sudden jump in oil and gas leakage. A more recent synthesis, highlighted by ScienceDaily coverage, framed the early-2020s surge as a period when the atmosphere temporarily lost much of its ability to destroy methane at the same time that flooded ecosystems became more productive sources.
This misalignment between early narratives and emerging evidence matters for policy and public trust. If observers reflexively blame every methane jump on fossil fuel operators, they risk overlooking powerful natural feedbacks that are accelerating under climate change. At the same time, the new findings do not exonerate human activity: industrial emissions created the background warming that primed wetlands to emit more, and human-driven NOx reductions reshaped atmospheric chemistry. The episode instead underscores how tightly coupled human actions and natural processes have become, and how simplistic attributions can obscure the more complex reality of Earth’s changing methane cycle.
Lessons for Climate Policy and Monitoring
The 2020 methane spike offers several lessons for climate strategy. First, it shows that focusing solely on emission cuts from fossil fuels and agriculture is not enough; policymakers must also account for how those cuts interact with atmospheric chemistry. Efforts to reduce NOx are essential for air quality and public health, but they can temporarily weaken the methane sink if not accompanied by stronger controls on methane itself. One implication is that rapid deployment of methane-targeted measures—such as leak detection in energy systems, manure management in livestock operations, and capture of landfill gas—becomes even more critical as cleaner combustion technologies roll out.
Second, the episode highlights the importance of integrated observation systems that can distinguish between changes in sources and changes in sinks. Surface flask networks like NOAA’s provide invaluable long-term baselines, but they are most powerful when combined with satellite retrievals, regional flux estimates, and chemical transport models. ESA’s work on wetland emissions and NASA’s analysis of oxidant chemistry illustrate how multiple data streams can be woven together to explain anomalies that would otherwise remain puzzling. Building out this kind of multi-platform monitoring will be essential for spotting future shifts in the methane cycle early enough to respond.
Finally, the pandemic-era surge serves as a warning that natural feedbacks may already be exerting greater influence on greenhouse gas trends than many models assume. As wetlands expand or intensify their emissions under a warmer, wetter climate, they could erode some of the gains achieved through human mitigation efforts. That does not diminish the value of cutting fossil fuel and agricultural methane; instead, it raises the bar for how ambitious and coordinated those cuts must be. The 2020 spike was not just an oddity of lockdown life—it was a stress test of the Earth system that revealed vulnerabilities in both natural and human-managed components of the methane budget, and it will likely shape how scientists and policymakers think about this potent greenhouse gas for years to come.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
