By measuring the carbon-14 isotope in air from more than 200 years ago, the researchers found that scientists have been vastly overestimating the amount of fossil methane emitted by natural sources, and have therefore been underestimating the amount of methane humans are emitting into the atmosphere via fossil fuels.
Methane is a powerful greenhouse gas and large contributor to global warming. Methane emissions to the atmosphere have increased by approximately 150 percent over the past three centuries, but it has been difficult for researchers to determine exactly where these emissions originate; heat-trapping gases like methane can be emitted naturally, as well as from human activity.
University of Rochester researchers Benjamin Hmiel, a postdoctoral associate in the lab of Vasilii Petrenko, a professor of earth and environmental sciences, and their collaborators, measured methane levels in ancient air samples and found that scientists have been vastly underestimating the amount of methane humans are emitting into the atmosphere via fossil fuels. In a paper published in Nature, the researchers indicate that reducing fossil fuel use is a key target in curbing climate change.
“Placing stricter methane emission regulations on the fossil fuel industry will have the potential to reduce future global warming to a larger extent than previously thought,” Hmiel says.
Methane is the second largest anthropogenic—originating from human activity—contributor to global warming, after carbon dioxide. But, compared to carbon dioxide, as well as other heat-trapping gases, methane has a relatively short shelf-life; it lasts an average of only nine years in the atmosphere, while carbon dioxide, for instance, can persist in the atmosphere for about a century. That makes methane an especially suitable target for curbing emission levels in a short time frame.
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