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RESEARCH-METHANE-GREENHOUSE
Ancient methane unlikely to cause massive greenhouse gas release
WASHINGTON, Feb 21, 2020 (BSS/XINHUA) – U.S. researchers have found that
methane stored in permafrost and ocean is unlikely to cause massive
greenhouse gas release.
The study published on Thursday in the journal Science showed that even if
methane is released from these large natural stores in response to warming,
very little actually reaches the atmosphere.
Permafrost in the soil and methane hydrates deep in the ocean are large
reservoirs of ancient carbon.
Researchers at the University of Rochester drilled and collected ice cores
from Taylor Glacier in Antarctica. The ice core samples contain tiny air
bubbles with small quantities of ancient air trapped inside, acting like time
capsules.
They used a melting chamber to extract the ancient air from the bubbles and
then measured the composition of air from the time of Earth’s last
deglaciation 8,000 to 15,000 years ago.
“The time period is a partial analog to today, when Earth went from a cold
state to a warmer state,” said the paper’s co-author Michael Dyonisius with
Rochester in a statement. “But during the last deglaciation, the change was
natural. Now the change is driven by human activity, and we’re going from a
warm state to an even warmer state.”
Analyzing the carbon-14 isotope of methane in the samples, the group found
that methane emissions from the ancient carbon reservoirs were small,
suggesting that the likelihood of those old carbon reservoirs destabilizing
and creating a large positive warming feedback in the present day is low.
If the methane is released in the deep ocean, most of it is dissolved and
oxidized by ocean microbes before it ever reaches the atmosphere. If the
methane in permafrost forms deep enough in the soil, it may be oxidized by
bacteria that eat the methane, according to the study.
“One of our take-home points is that we need to be more concerned about the
anthropogenic emissions — those originating from human activities — than
the natural feedbacks,” said Dyonisius.
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