Thawing Permafrost Releases Unexpected Levels of Greenhouse Gases, Including Methane

New York Times
December 16, 2011

As Permafrost Thaws, Scientists Study the Risks 
Justin Gillis

Permafrost, or perennially frozen ground, underlies nearly a quarter of the Northern Hemisphere. In the Arctic regions where permafrost is found, temperatures are warming at a much faster rate than in the regions closer to the equator. Up to now, the Arctic has been absorbing carbon, on balance, and was once expected to keep doing so throughout this century. But recent analyses suggest that the permafrost thaw could turn the Arctic into a net source of carbon, possibly within a decade or two. Across huge areas, including much of central Alaska, permafrost is hovering just below the freezing point, and is expected to start thawing in earnest as soon as the 2020s.

Scientists are struggling to understand the implications of thawing permafrost on climate change. A recent study suggests that permafrost contains twice as much carbon as the entire atmosphere. An unexpected development is the amount of methane that could be released into the atmosphere as permafrost thaws. Methane has 23 times the global warming potential – the potency of trapping the sun’s heat –as carbon dioxide (CO2). The potential for large new methane emissions in the Arctic is one of the biggest wild cards in climate science. According to the recent study published in NATURE:

“Arctic temperatures are rising fast, and permafrost is thawing. Carbon released into the atmosphere from permafrost soils will accelerate climate change, but the magnitude of this effect remains highly uncertain. Our collective estimate is that carbon will be released more quickly than models suggest, and at levels that are cause for serious concern. We calculate that permafrost thaw will release the same order of magnitude of carbon as deforestation if current rates of deforestation continue. But because these emissions include significant quantities of methane, the overall effect on climate could be 2.5 times larger.”

While preliminary computer analyses suggest that the Arctic and sub-Arctic regions could eventually become an annual source of carbon equal to 15 percent or so of today’s yearly emissions from human activities, this study estimated that if human fossil-fuel burning remained high and the planet warmed sharply, the gases from permafrost could eventually equal 35 percent of today’s annual human emissions. Andy Revkin, a former colleague of this author while at Pace University, has written extensively on this issue in his Dot Earth blog.