Biomass in the environment drove more methane production than fossil fuels between 2020 and 2022, the analysis finds.

Environmental pollutants, not fossil fuels, are driving the recent increase in methane emissions worldwide, according to a new, detailed analysis published Oct 28 in Bulletin of the National Academy of Sciences by CU Boulder researchers and colleagues.

“Understanding where methane comes from helps us guide effective mitigation strategies,” said Sylvia Michel, senior research associate at the Institute for Arctic and Alpine Research (INSTAAR) and doctoral student in the Department of Atmospheric and Oceanic Sciences. CU Boulder. . “We need to know more about those emissions to understand what kind of climate we can expect in the future.”

Methane is a greenhouse gas that accounts for a third of global warming since industrialization. Although the atmosphere contains less methane than carbon dioxide, methane traps about 30 times more heat than carbon dioxide over a 100-year period, making it an important target for dealing with climate change.

“Methane levels in the atmosphere have nearly tripled since the 1700s,” said co-author Jianghanyang (Ben) Li, an assistant professor in the Department of Atmospheric and Oceanic Sciences and INSTAAR.

But unlike CO₂which can remain in the atmosphere for thousands of years, methane breaks down within ten years. As a result, dealing with the heat of methane can have a quick and strong impact to reduce the rate of warming, making it a “very low yield,” Li said.

Although the results suggest that microbes have been emitting more methane than fossil fuels in recent years, reducing the use of fossil fuels remains the key to solving climate change, the team it said. Reducing food waste and eating less red meat can also help lower carbon dioxide emissions.

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Previous studies suggest that fossil fuel production is responsible for about 30% of global methane production.

But biological sources—such as wetlands, cattle and garbage—are an even more important source of methane, which accounts for more than half of the world’s emissions. Archaea, a type of bacteria that live in soil and cow intestines, produce methane as a by-product of organic matter.

Michel and Li have been working with Boulder’s Global Monitoring Laboratory (GML) at the National Oceanic and Atmospheric Administration (NOAA) for years.

The lab receives air samples from 22 locations around the world every week or two. Researchers then separate the different components of the atmosphere – such as CO₂ or methane-for analysis.

By analyzing the types of carbon atoms, or isotopes, that a sample of methane contains, Michel, Li and the team can determine its source. For example, methane from fossil fuels has more of the isotope carbon-13 than methane in the air, and methane from biological sources has less carbon-13. The lab has been measuring methane isotopes since 1998.

Scientists have seen a rapid increase in atmospheric methane levels since 2007, after a period of stability in the early 21st century. In 2020, NOAA recorded the highest rate of methane growth since it began collecting data in 1983, and that record was broken again in 2021.

At the same time, Michel noticed a surprising decrease in the carbon-13 isotope over the past 17 years. He and the team set out to understand what was driving it.

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Using computer simulations, Michel and his team modeled three different concentrations of the gas to see which would leave an isotopic signature similar to the one seen.

They found that between 2020 and 2022, the largest increase in atmospheric methane was driven entirely by biological sources. Since 2007, scientists have seen microbes play an important role in methane emissions, but their contribution has risen to more than 90% as of 2020.

Xin (Lindsay) Lan, a scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU Boulder, said: “Some preliminary studies have shown that human activities, particularly fossil fuels, are has been a major source of methane growth in recent years.He leads the NOAA greenhouse gas trends report on GML.

“These studies failed to look at the isotope profile of methane, which could lead to a different conclusion and an incomplete picture of global methane.”

It is still unclear whether the increase in biological emissions is from natural sources such as wetlands or human-driven sources, such as litter and agriculture. The team plans to investigate further to determine the exact source of the methane.

“In a warming world, it would not be surprising if any of these sources emit more methane,” said Michel, who explained that organisms, like humans, tend to have a higher metabolism when to warm up. “As a result, more methane can stay in the atmosphere to accelerate global warming. So we need to address the climate problem, and that means dealing with CO.₂ emissions.”