According to a study by the University of Colorado at Boulder, the microbes living in environments like wetlands and cattle herds are a significantly greater source of methane, accounting for more than half of the global emissions.
Methane is among the most potent greenhouse gases with 28 times global warming potential than carbon dioxide, and accounts for a third of the world’s warming. While methane emissions have surged since industrialization, it followed a short pause from 1999 to 2006 due to reduced biomass burning.
Despite the reduction in biomass burning, the National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory (NOAA) reported that methane emissions have been increasing since 2007, and reached a record high between 2020 and 2022. The mechanisms that accelerated the emission were unclear so far.
“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,” said Sylvia Michel, a senior research assistant.
Researchers found links between climate change and extreme weather
Using computer simulations, researchers studied the different scenarios to account for what emits isotopes similar to the ones observed. Researchers could identify the source using the methane samples.
For instance, methane released from fossil fuels has more carbon-13 isotope than methane in the air. Meanwhile, the microbial source releases methane with even less carbon-13 isotope.
After studying the air samples from 22 sites, the team found that microbial sources heavily drove the drastic increase in atmospheric methane (between 2020 and 2022).
Scientists are unclear whether the emissions came from natural sources like wetlands or anthropogenic sources like waste and agriculture. But with the recent understanding of microbes’ role, scientists have observed that their contribution has surged to 90% in 2020.
Lakes Could be an Unsuspected Source of Methane
“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,” said Xin Lan.
Unlike carbon dioxide, methane has a lower atmospheric residence time, vanishing within a decade. Therefore, addressing methane emissions can offer immediate results against tackling global warming.
“In a warming world, it wouldn’t be surprising if any of these sources emitted more methane. 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,” said Michel.
Ozone pollution reduces new yearly growth in tropical forests
Journal Reference
Michel, S. E., Lan, X., Miller, J., Tans, P., Clark, J. R., Schaefer, H., Sperlich, P., Brailsford, G., Morimoto, S., Moossen, H., & Li, J. (2024). Rapid shift in methane carbon isotopes suggests microbial emissions drove record high atmospheric methane growth in 2020–2022. Proceedings of the National Academy of Sciences, 121 (44), e2411212121. DOI: 10.1073/pnas.2411212121