New estimates boost permafrost contribution to climate change

An international group of researchers believes greenhouse gases from thawing permafrost will be released at a much faster rate than previously estimated, which could have significant implications for climate change projections.

A survey of 41 scientists — including seven University of Alaska Fairbanks researchers — estimates the amount of carbon released from thawing permafrost by 2100 will be 1.7 to 5.2 times larger than previously estimated. Their conclusions, reported Wednesday in the scientific journal Nature, describe permafrost thawing as a likely accelerator of global warming.

“Our collective estimate is that carbon will be released more quickly than models suggest, and at levels that are cause for serious concern,” the article states.

The higher figures come about because of an ongoing reevaluation of the carbon stored in permafrost.

In most soils such material is typically in the top several feet, but in frozen soils those carbon-filled sediments can be much deeper.

Because of that, the estimated amount of carbon stored in northern soils has tripled in recent years, to roughly 1,700 billion tons. That’s four times more than all the carbon emitted by human activity since the Industrial Revolution and twice as much as is currently present in the atmosphere.

“Soils in the north are cold,” said Ben Abbott, a UAF doctoral student at the Institute of Arctic Biology and co-author of the Nature article. “It’s like a big refrigerator, and all that material is just stored.”

With that much carbon-filled material present, a small change in the estimated amount released could make a notable difference in climate change projections. Most scientists believe gases such as carbon dioxide and methane, both of which are released by warming permafrost, contribute to global warming.

But researchers studying northern areas with permafrost have admittedly sparse data, said Ted Schuur, a University of Florida professor who co-authored the article. Because of that, he said, numerous members of the Permafrost Carbon Research Network were surveyed to collect a larger picture, combining scientific data with their predictions. A National Science Foundation grant paid for the work.

“We don’t know exactly what’s going to happen, but these are probably the best people to ask,” Schuur said.

Abbott said all the scientists in the survey felt existing models were too conservative in their projection of emissions from thawing permafrost. He said most, including him, thought the amount of carbon released would be roughly three to four times the current estimates.

The release of methane from thawing permafrost is considered an important ingredient, because it’s 25 times more potent as a greenhouse gas than carbon dioxide. Even though it represents about 2 to 3 percent of the emissions from melting permafrost, Abbott said, it could account for about half the warming.

If thawing happens at the rate the scientists believe it will, its greenhouse effect will match that of worldwide deforestation, according to the article. It still concludes, however, that fossil fuel consumption will be the biggest factor in the next century.

“It’s not likely to overshadow what’s being burned by humans, but that doesn’t mean it’s not important,” Schuur said. “It’s something that could amplify the change that’s already going on.”


Read more: Fairbanks Daily News-Miner - New estimate boosts permafrost contribution to climate change