An international team of researchers, including scientists from Utrecht University and the University of Maryland, has reconstructed the concentration of clumped isotopes of methane in air from the past for the first time. This provides new insights into how atmospheric methane concentrations have changed since the start of the industrial era, around 1850. For the study, the scientists used air that was roughly 40 years old, preserved in compacted snow (firn) in Greenland. The results were published in Science Advances.
Methane is the second most important greenhouse gas after CO2, responsible for around 30% of global warming to date. Atmospheric methane concentrations are rising, but it is not yet fully understood why.
Human fingerprint
The researchers' measurements and analyses showed that the concentration of clumped methane isotopes, rare methane molecules with two heavy atoms clustered together, has changed significantly over the past decades. At first, the researchers couldn't fully explain this shift, but after running model simulations of the atmosphere spanning the past 1,000 years, they were able to pinpoint a cause.
"Since the start of industrialization, humans have disrupted the balance between methane emissions and breakdown so profoundly that it's visible in our measurements," explains Malavika Sivan, first author of the study.
Methane balance
The clumped isotope signal reflects the balance between how much methane is emitted and how much is removed from the atmosphere. That balance determines whether atmospheric methane concentrations keep rising or start to fall. With this information, researchers can reconstruct the methane balance over time and going forward, allowing them to check whether measures taken to reduce methane emissions are working.
That matters, says Thomas Röckmann, professor of atmospheric physics and chemistry. "Reducing methane concentrations is one of the fastest ways to slow global warming in the short term." Continued human emissions and possible climate feedback from natural sources could drive further increases. "Policy initiatives like the Global Methane Pledge, which aims for a 30% cut in methane emissions by 2030 compared with 2020, might help slow or reverse that trend," Röckmann explains.
A surprising measurement
The research was prompted by an unexpected finding: The researchers measured clumped methane isotopes in the current atmosphere. The occurrence of these molecules was far higher than in methane from known sources such as wetlands, agriculture and fossil fuels. Those sources couldn't account for such a strong signal.
The team concluded that the clumped isotope signal must originate from methane removal—when methane breaks down in the atmosphere through reactions with other substances. These clumped molecules react more slowly than normal methane molecules. "Following this, we wondered if we could use these clumped methane signatures to learn how the removal reactions changed in the atmosphere over time," Röckmann explains.
Forty-year-old air
Methane is mainly released from biological and fossil sources. It forms naturally in wetlands, rice paddies, landfills and agricultural systems, and is also released from fossil fuels such as coal, oil and natural gas. To understand how methane sources and removal have changed over time, the researchers needed access to air from the past. And not just a little: Analyzing clumped methane isotopes requires as much as 1,000 liters (264 gallons) of air.
That old air can be found in firn: a layer of dense snow between the surface and the underlying glacial ice, where air that is sometimes up to 70 years old remains trapped. At the EastGRIP research station in Greenland, Röckmann collected the necessary air samples by drilling deep into the snow and essentially pumping the air out with specialized equipment.
"We collected 500–700-liter (132–185-gallon) air samples that were up to 40 years old," Röckmann says. "Analyzing that air tells you a lot about the composition of the atmosphere in the past."
International collaboration
The amount of air was still on the low end for reaching the best precision with the instrument used in Utrecht. But a research group at the University of Maryland had a different instrument that could make the same measurements using less air. Sivan traveled to the University of Maryland for two months to analyze the air samples with her colleague Jiayang Sun. "There was a lot of trial and error, but in the end, we were excited to see such a strong temporal change in the clumped isotope signal."
The results were unexpected, and it took a lot of discussion and modeling to understand the measured signal. "But it was worth it: We really understand how the clumped isotope signal records the influence of humans on the atmosphere in the industrial period," Sivan says.
Publication details
Malavika Sivan et al, Anthropogenic perturbations to atmospheric methane reflected in Greenland firn air clumped isotope measurements, Science Advances (2026). DOI: 10.1126/sciadv.aeb2203. www.science.org/doi/10.1126/sciadv.aeb2203
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Citation: Air from Greenland snow shows industrialization's impact on atmospheric methane (2026, July 16) retrieved 16 July 2026 from https://phys.org/news/2026-07-air-greenland-industrialization-impact-atmospheric.html
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