Atmospheric methane concentrations have been climbing steadily since 2019, causing alarm about whether the world is losing ground on one of its most important climate targets. A new study offers a detailed account of what’s driving that rise (Sci. Adv. 2026, DOI: 10.1126/sciadv.adz9007).
A team led by researchers at Harvard University used a novel combination of satellite instruments to track methane emissions and atmospheric chemistry year by year from 2019 to 2024.
The TROPOMI instrument, aboard the European Sentinel-5P satellite, measures methane across the entire globe every day, but has known measurement biases. The team corrected those biases using data from the Japanese GOSAT satellite, which takes fewer but more accurate measurements, applying machine learning to blend the two datasets. “It’s a nice solution to a difficult calibration problem,” says Alex Turner, an atmospheric scientist at the University of Washington who was not involved in the study.
The approach allowed them to separately track two things that can cause atmospheric methane levels to rise—increasing methane emissions and changes in the concentration of hydroxyl radicals, molecules in the atmosphere that break down methane.
They found that the largest contributor to the 2019–24 rise (an increase of 59%) is simply momentum. By 2019, the world was already emitting more methane than the atmosphere could destroy, so concentrations were on track to keep rising for years even if nothing changed.
Emissions spiked in 2021, largely from livestock and waste—mainly landfills and wastewater treatment—before falling back to roughly 2019 levels by 2024. That temporary surge accounted for 25% of the increase. The remaining 16% came from a dip in hydroxyl radical concentrations.
“The recent slowdown in the methane growth rate after 2022 is mostly due to recovering OH rather than decreasing emissions,” author Megan He says. The atmosphere’s chemistry improved on its own, not because of a reduction in emissions.
Turner calls the study a useful contribution, but notes that a different analysis published in February indicates that OH plays a much larger role. He says that both studies appear methodologically sound. So, resolving that disagreement will likely require new kinds of measurements (Science, 2026, DOI: 10.1126/science.adx8262).
While there is some disagreement about the atmospheric contribution to methane levels, the long-term rise in methane is clearly driven by human activity. “There is no ambiguity there,” Turner says.
Over 150 countries have signed the Global Methane Pledge, committing to cut 30% of anthropogenic emissions by 2030. The Harvard study finds real progress in reducing methane emissions from production of oil, gas, and rice. But those gains were more than offset by increasing emissions from livestock and waste.
CORRECTION
This story was updated on April 14, 2026, to clarify that the older study reporting higher hydroxyl radical contribution to atmospheric methane levels was published in February and not in March.
2026 American Chemical Society
