Methane is a very potent greenhouse gas that has made up around one third of the earth's warming since the time of industrialization. The atmosphere may not contain as much methane as it does carbon dioxide, but the key thing to note is that methane can trap around 30 times more heat than CO2 does across a century.
With the concentrations of methane in the air nearly tripling since the 1700s, this is a topic of great interest to climate scientists.
The research was carried out by scientists from University of Colorado Boulder, who analyzed air samples collected by Boulder’s Global Monitoring Laboratory at the National Oceanic and Atmospheric Administration from 22 sites around the world roughly every one to two weeks. By isolating different components of the collected air, including methane and carbon dioxide, they can use the carbon isotopes in each sample to identify its source.
NOAA reported the biggest jump in methane in 2020 since it started collecting this data in 1983, and the trend continued in 2021. Study lead author Sylvia Michel also noticed that the carbon-13 isotope in these samples has been dropping over 17 years, so she sought to identify the cause.
“Understanding where the methane is coming from helps us guide effective mitigation strategies. We need to know more about those emissions to understand what kind of climate future to expect,” Michel noted.
Her team modeled various emissions scenarios to find out which one would create the type of isotopic signature that actually took place, and they found that the dramatic rise in atmospheric methane recorded between 2020 and 2022 was actually the result of microbial sources. In fact, microbes have been playing a growing role in methane emissions since 2007; by 2020, they were making up an incredible 90% of these emissions.
A scientist for the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU Boulder and NOAA, Xin Lan, explained where those blaming fossil fuels have been going wrong.
“Some prior studies have suggested that human activities, especially fossil fuels, were the primary source of methane growth in recent years. 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 said.
Next, the researchers plan to employ advanced methodologies and tools to further break down the exact microbial sources of the methane. Although microbes associated with human-related activities such as agriculture, landfills, and livestock farming also contribute, one big source of methane emissions from microbes is wetlands.
Microbes in tree bark absorb a surprising amount of methane
Interestingly, a study that was recently published in the journal Nature revealed that the microbes in tree bark are actually quite good at absorbing methane, taking up between 25 and 50 million metric tons of it each year.
Although the specific amount of methane they capture depends on the species of the tree and its growing environment, they concluded that trees capture a lot more methane than they emit. This suggests that reforestation efforts could be very beneficial to the environment in the long run.
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