When we think about the Arctic in a warming world, we tend to think about sharp declines in sea ice and — that powerful symbol — the polar bear. But that’s far from the only problem that a melting Arctic brings.
In the past decade, scientists have been training more attention on another deeply troubling consequence. Rapid Arctic warming is expected to lead to the thawing of a great deal of frozen soil or permafrost, which, as it thaws, will begin to emit carbon dioxide and methane to the atmosphere. And if this occurs in the amounts that some scientists are predicting, it could significantly undermine efforts to reduce the world’s greenhouse gas emissions.
Indeed, scientists have discovered a simple statistic that underscores the scale of the potential problem: There may be more than twice as much carbon contained in northern permafrost as there is in the atmosphere itself. That’s a staggering thought.
Permafrost is simply defined as ground that stays frozen all year round. There’s a lot of it – it covers 24 percent of the surface of the northern hemisphere land masses, according to the International Permafrost Association. But more and more of it is thawing as the Arctic warms, and these frozen soils contain a vast amount of organic material — largely dead plant life — in a kind of suspended animation.
“It’s built up over thousand and thousands of years,” says Robert Max Holmes, a senior scientist at the Woods Hole Research Center. “It’s all stored away in a freezer, and as we’re warming the Earth, and warming the Arctic, it’s starting to thaw.”
As permafrost thaws, microbes start to chow down on the organic material that it contains, and as that material decomposes, it emits either carbon dioxide or methane. Experts think most of the release will take the form of carbon dioxide — the chief greenhouse gas driving global warming — but even a small fraction released as methane can have major consequences. Although it doesn’t last nearly as long as carbon dioxide in the atmosphere, methane has a short-term warming effect that is many times more powerful.
Among the potential mega-problems brought on by climate change, including melting ice caps to the slowdown of the ocean conveyor system, permafrost emissions are unique. For it’s not merely about sea level rise or weather changes — it’s about amplifying the root problem behind it all, atmospheric carbon levels.
The emission of carbon from thawing permafrost is what scientists call a “positive feedback.” More global warming could cause more thawing of Arctic permafrost, leading to more emissions of carbon into the atmosphere, leading to more warming and more thawing of Arctic permafrost — this does not end in a good place.
Moreover, in a year in which the world will train its attention on Paris and the hope for a new global climate agreement, permafrost emissions could potentially undermine global climate policies. Even as the world starts to cut back on emissions, the planet itself might start replacing our emissions cuts with brand new carbon outputs.
All of this, and the Arctic permafrost problem hasn’t received much attention — yet. “The concept is actually relatively new,” says Kevin Schaefer of the National Snow and Ice Data Center at the University of Colorado in Boulder. “It was first proposed in 2005. And the first estimates came out in 2011.” Indeed, the problem is so new that it has not yet made its way into major climate projections, Schaefer says.