Fears a thawing of permafrost could accelerate global warming by putting substantial amounts of methane and carbon dioxide into the atmosphere have been contradicted in a study in the journal Science.
In September 2006, the journal Nature claimed greenhouse gases long residing in permafrost were escaping into the atmosphere in larger amounts than previously believed. The Nature article prompted Chris Field, director of global ecology at the Carnegie Institution in Washington, DC, to tell USA Today at the time, “The higher the temperature gets, the more permafrost we melt, the more tendency it is to become a more vicious cycle. That’s the thing that’s scary about the whole thing. There are lots of mechanisms that tend to be self-perpetuating, and relatively few that tend to shut it off.”
Difficult to Melt
But a study led by Duane G. Froese of the University of Alberta concludes permafrost is far more resistant to climate change than previously claimed. The study, “Ancient Permafrost and a Future, Warmer Arctic” (Science, September 19, 2008), examines ancient ice, determined to be 740,000 years old, found in the Yukon. The permafrost has, indeed, remained “permanent” despite having experienced climate change—both warming and cooling—for hundreds of thousands of years.
Ice core samples, for example, show temperatures were repeatedly warmer in the Arctic during the past 740,000 years than they are today.
The Froese study calls into question the accuracy of climate models predicting long-term damage to permafrost from global warming. The study authors put it as follows:
“Climate models predict extensive and severe degradation of permafrost in response to global warming, with a potential of the release of large volumes of stored carbon. However, the accuracy of these models is difficult to evaluate because little is known of the history of permafrost and its response to past warm intervals of climate. We report the presence of relict ground ice in subarctic Canada that is greater than 700,000 years old, with the implication that ground ice in this area has survived past interglaciations that were warmer and of longer duration than the present interglaciation.”
Reality Contradicts Models
William D. Balgord, Ph.D., president of Environmental & Resources Technology, Inc., a Middleton, Wisconsin-based consulting firm, also doubts the models’ ability to reflect the complex realities of the geophysical world.
“The 2006 Nature article is long on implications for severe melting of permafrost, predicted by the author’s crafted model, but short on evidence that melting is proceeding at an adequate rate and sufficiently long time to set in play the positive feedback loop described by Chris Field,” said Balgord.
“What he and other pro-warming advocates ignore is overwhelming evidence of strong negative feedbacks in place, resisting changes that might disrupt global climate patterns beyond the envelope of natural variability,” Balgord added. “To cite another example, the Holocene [the current geological period that has existed since the retreat of the last continental glaciers in the Northern Hemisphere] has been firmly in place now for some 12,000 years. During this period, sea levels have not risen or fallen significantly from their current positions, clear evidence of a climatic ‘still-stand.'”
Geologists define permafrost as soil at or below the freezing point for two or more years. Most permafrost is located at high latitudes (those in close proximity to the North and South Poles), but alpine permafrost may also be found at high altitudes farther away from the poles.
Bonner R. Cohen, Ph.D. ([email protected]) is a senior fellow at the National Center for Public Policy Research in Washington, DC.