Nature Communications study uses methane isotopes for a more precise emissions map
A team of researchers has combined satellite measurements with isotopic data from the ground and revised earlier estimates of tropical methane emissions, with more than expected from East Asia and Central Africa and less from the Amazon basin.
An international team of researchers published in May 2026 in Nature Communications (DOI 10.1038/s41467-026-72668-2) a study that uses methane isotopes, the different forms of the methane molecule with varying ratios of carbon-12 and carbon-13, to pin down more precisely where the world’s emissions of this gas are formed and how they are changing. Under the new estimates, methane emissions from East Asia, particularly China, and from Central Africa and South Asia, particularly India, are higher than standard methods without isotope data have so far been calculating. Emissions from the Amazon basin, by contrast, are lower than had been estimated.
Methane is the second most important anthropogenic greenhouse gas after carbon dioxide. According to the World Meteorological Organization (WMO), the atmospheric concentration of methane in 2025 reached around 1,935 parts per billion (ppb), more than 160 percent above pre-industrial levels. Although its mean lifetime in the atmosphere is around 12 years, far shorter than carbon dioxide, methane has a radiative impact some 80 times stronger over the first 20 years. For this reason, precisely identifying the sources is directly relevant for the emission-reduction policies under the Global Methane Pledge, signed by more than 150 countries since 2021.
Methodologically, conventional satellite measurements of methane, made by instruments such as Europe’s TROPOMI and the US MethaneSAT, give estimates of the total concentration of the gas over a given region, but cannot tell the sources apart. The isotopic approach helps because different sources, biogenic from wetlands and rice paddies, fossil from oil and natural gas, or biomass burning, have a different signature in the carbon-12 to carbon-13 ratio. By combining this information with atmospheric measurements, the team has recalibrated the global inventory of emissions for the period 2019 to 2021 and shown that earlier assessments had over-estimated biogenic sources at tropical latitudes and under-estimated fossil and biogenic sources in Asia.
What the study does NOT prove
While the result matters, it is worth separating what the new calculation actually shows from wider conclusions. First, the study does not claim that China or India are “to blame” for the global rise in atmospheric methane. What is established is that the regional distribution of emissions diverges from earlier models, which means the mechanisms need to be pinned down more carefully, whether these are leaking gas pipelines, coal mines, livestock or rice fields. Without source differentiation, the calculation does not allow emission-reduction policy to be targeted directly.
Second, the period of the study covers only three years, from 2019 to 2021, which partly straddled the unusual conditions of the COVID-19 pandemic. The pandemic temporarily reduced industrial activity, which may have affected the proportions of fossil and biogenic emissions in the sample. The authors stress that future studies should extend the analysis to the 2022-2025 period, by which time the global economy would have settled into a new rhythm.
A third important element is the fact that the rise in atmospheric methane in 2024, which is also the subject of a separate study in the same series in Nature Communications, appears to be coming chiefly from natural sources, particularly tropical wetlands responding to rising humidity and temperature. That means climate change can on its own amplify the methane cycle through a positive feedback loop, which makes cutting anthropogenic emissions all the more urgent. The next global report on national contributions under the Paris Agreement is expected ahead of the COP31 summit in Antalya, on 9-20 November 2026, and will be the moment for signatory countries of the Global Methane Pledge to present updated data on emission reductions since 2020.
In terms of measurement technology, the isotopic approach has until recently been confined to ground stations, of which there are fewer than a hundred worldwide, well short of what good global characterisation requires. The development of satellite instruments capable of distinguishing methane isotope forms from orbit, such as the Franco-German MERLIN mission, scheduled for launch in 2027, would deliver the first real-time global isotopic view. Until then, combining archived satellite data with ground-based isotopic measurements, as the team in this study has done, remains the best method. The next results from the same team are expected in the autumn of 2026, when the 2022-2024 period will also be analysed, covering the record global rise in methane concentration.
