New research led by CU Boulder shows that microbes, not fossil fuels, have been the key drivers behind the surge in methane emissions between 2020 and 2022. This discovery could shift focus towards different mitigation strategies to combat climate change.
Microbes in the environment have been the primary drivers of the recent spike in global methane emissions, rather than fossil fuels, according to a detailed analysis published in the Proceedings of the National Academy of Sciences. The groundbreaking study comes from researchers at CU Boulder and their collaborators.
“Understanding where the methane is coming from helps us guide effective mitigation strategies,” Sylvia Michel, a senior research assistant at the Institute of Arctic and Alpine Research (INSTAAR) and a doctoral student in the Department of Atmospheric and Oceanic Sciences at CU Boulder, said in a news release. “We need to know more about those emissions to understand what kind of climate future to expect.”
Methane, a potent greenhouse gas, is responsible for about one-third of global warming since the industrial era began. Although it is less abundant than carbon dioxide, methane’s ability to trap heat is roughly 30 times more potent over a century, making it a crucial focus in climate mitigation efforts.
“Methane concentrations in the air have almost tripled since the 1700s,” co-author Jianghanyang (Ben) Li, an assistant professor in the Department of Atmospheric and Oceanic Sciences at CU Boulder and INSTAAR, said in the news release.
Methane degrades within a decade, unlike carbon dioxide which can linger in the atmosphere for thousands of years. Hence, reducing methane emissions can yield immediate and substantial benefits in combating climate change. This makes it a “low-hanging fruit,” according to Li.
The study underscores that while fossil fuel production has historically contributed significantly to methane emissions, microbial sources, such as wetlands, cattle and landfills, are now the dominant contributors. Archaea — microorganisms residing in the soil and the guts of cows — release methane as they break down organic material.
Michel and Li have collaborated with the Global Monitoring Laboratory (GML) at the National Oceanic and Atmospheric Administration (NOAA) over the years. By isolating components like CO2 and methane from air samples collected from 22 sites worldwide, they use the carbon isotope signatures to trace the methane’s origin. Fossil fuel methane contains more carbon-13 than microbial methane.
Since 2007, atmospheric methane levels have climbed steadily, with the most rapid increases reported in 2020 and 2021. The NOAA reported the highest growth rate of methane since it began collecting data in 1983 during these years. Parallelly, a significant decline in the carbon-13 isotope was observed, prompting Michel and her team to investigate further.
Through computer simulations, the team determined that the drastic growth in methane since 2020 was primarily due to microbial sources. Since then, over 90% of the increase in methane emissions has been attributed to microbes.
“Some prior studies have suggested that human activities, especially fossil fuels, were the primary source of methane growth in recent years,” added Xin (Lindsay) Lan, a scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU Boulder and NOAA, who leads NOAA’s global greenhouse gas trends reporting at the 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 emissions,” she added.
While the team has significantly advanced understanding, the exact sources of increased microbial emissions — whether natural like wetlands or human-driven like agriculture and landfills — remain undetermined. Further investigations are planned to pinpoint these origins.
“In a warming world, it wouldn’t be surprising if any of these sources emitted more methane,” added Michel. “Consequently, more methane could stay in the atmosphere to accelerate global warming. So we need to address the climate crisis, and that really means addressing CO2 emissions.”