Ancient Stores of Methane May Not Be Climate Threat

(CN) – Massive pockets of carbon trapped around the world under frozen soil and in the depths of the ocean have long worried climate scientists – but they may not be the threat to our atmosphere they have been made out to be.

A study released Thursday in the journal Science details how a team of researchers looked at key points throughout Earth’s history in an effort to better understand how our planet’s atmosphere responds to methane, a greenhouse gas often viewed as a powerful contributor to rising global temperatures.  Researchers wanted to explore the relationship between rising temperatures and Earth’s ancient carbon reservoirs, great collections of carbon and methane that have been stored for centuries underneath permanently frozen ground and in the ocean’s depths.

This image taken from a helicopter in the High Arctic shows cracks in the permafrost. (Brocken Inaglory/Wikipedia)

Climate scientists have long been wary of these carbon pockets. They previously feared rising temperatures will thaw the permafrost and cause oceans to heat up, causing the release of these gases into Earth’s already overloaded atmosphere.

But the researchers found most of these fears are unsupported by Earth’s own natural chemical history.

To make these observations, scientists collected and drilled through ice core samples taken from the Taylor Glacier in Antarctica. They then used advanced chemical dating and analysis techniques to study air pockets encased in the ice for thousands of years. Using the data taken from these air pockets, researchers were able to look at a time period on Earth around 8,000 to 15,000 years ago.

Michael Dyonisius, a graduate student at the University of Rochester and one of the authors of the study, says this time in Earth’s history experienced a similar degree of ice loss and deglaciation to what is seen today, and the comparisons can help us better understand how our planet behaves under such conditions.

“The time period is a partial analog to today, when Earth went from a cold state to a warmer state,” Dyonisius said with the release of the study. “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.”

Researchers examined the isotopes trapped in the ice samples and found that methane emissions from Earth’s older carbon pockets were remarkably small and had a relatively small chemical presence. Researchers say the chemical history suggests that if the same kind of emissions from ancient carbon reservoirs were to occur today, the chances of them significantly inflaming climate change are quite low.

Scientists believe that one the main reasons why the carbon from these pockets pose little threat is because there are so many potential buffers between the carbon and the atmosphere. The methane and carbon released from the ocean, for instance, can be mostly absorbed by the ocean’s natural microbes long before it reaches the ocean’s surface. The chemicals being released from the thawed ground can also be canceled out by the biological components of the soil, such as natural bacteria in the ground that can consume large amounts of methane.

Scientists believe these natural buffers have protected Earth’s atmosphere from carbon reservoir releases for much of our planet’s history, and there is every indication they will continue playing this role going forward.

Researchers say that while these results are good news, the dangers of greenhouse gas emissions from human activity are still very much a vital factor to consider.

Vasilii Petrenko, professor of earth and environmental sciences at the University of Rochester and a study co-author, says that looking at the vast differences between the emissions from the natural world and the emissions from human activity should highlight to the world where the root of the problem lies – and where our efforts need to be focused.

“Anthropogenic methane emissions currently are larger than wetland emissions by a factor of about two, and our data shows we don’t need to be as concerned about large methane releases from large carbon reservoirs in response to future warming; we should be more concerned about methane released from human activities,” Petrenko said with the release of the study.

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