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Human-made methane levels higher than previously believed (Image 2)

Loading ice core into melting chamber


Vasilii Petrenko loads an ice core into the melting chamber for extraction of trapped ancient air in order to study the chemical composition of the ancient atmosphere. [See related image Here.]

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In 2011, a team of researchers led by Vasilii Petrenko, an assistant professor of Earth and environmental sciences at the University of Rochester, spent seven weeks in Antarctica collecting and studying 2,000-pound samples of glacial ice cores dating back nearly 12,000 years. The ancient air trapped within the ice revealed surprising new data about methane that may help inform today’s policymakers as they consider ways to reduce global warming. The researchers were funded by the National Science Foundation (NSF).

A paper published about this research reported two important findings regarding methane, a powerful greenhouse gas and large contributor to global warming: (1) The risk that warming will trigger methane release from large natural reservoirs of ancient carbon seems to be low; and (2) humans are probably contributing more methane to the atmosphere through fossil fuel use and extraction than scientists previously believed. Therefore, reducing methane emissions from fossil fuels may be an even more important factor in reducing global warming.

"Our results are suggesting that anthropogenic (man-made) fossil fuel methane emissions are even larger than previously thought," Petrenko says. "This means we have even more leverage to fight global warming by curbing methane emissions from our fossil fuel use."

Petrenko’s lab is dedicated to understanding how both natural and man-made greenhouse gases respond to climate change. To do this, they analyze how past climate changes have affected greenhouse gases over time and the ways in which these gases might respond to future warming temperatures. In this case, Petrenko and colleagues used the ice cores extracted from Taylor Glacier to study past atmospheric records.

Every year that it snows in Antarctica, the current snow layer weighs on the previous layer, compacting over hundreds or thousands of years to eventually form layers of ice. These ice layers contain air bubbles, which are like tiny time capsules; using vacuum pumps and melting chambers, researchers are able to extract the ancient air contained within these bubbles and study the chemical composition of the ancient atmosphere.

The natural geologic methane levels the research team measured were three to four times lower than previously estimated numbers. If the natural geologic methane emissions are lower than expected, the anthropogenic fossil methane emissions must be higher than expected—Petrenko estimates by 25 percent or more. The study also suggests that the risk of methane release from natural ancient carbon reservoirs is lower than previously thought. [Research supported by NSF grant PLR 08-39031.]

To learn more, see the University of Rochester news story Icy air reveals human-made methane levels higher than previously believed. (Date image taken: December 2011; date originally posted to NSF Multimedia Gallery: Nov. 15, 2017)

Credit: Xavier Fain

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