The trouble is that the Arctic is warming faster than anywhere in the world. And there are tons - literally, hundreds of billions of tons - of global warming gases currently sequestered in the permafrost there. And if the permafrost were to melt, all those gases would be released, which would warm the arctic, which would melt the permafrost, which would release more greenhouse gases... you see the problem. From the article:
Methane (CH4) has at least 20 times the heat-trapping effect of an equivalent amount of carbon dioxide (CO2). As warmer air thaws Arctic soils, as much as 55 billion tons of methane could be released from beneath Siberian lakes alone, according to Walter’s research. That would amount to 10 times the amount currently in the atmosphere...
Today, 20% of Earth's land surface is locked up in a deep freeze. But scientists predict that air temperature in the Arctic is likely to rise as much as 6 degrees Celsius, or 10.8 degrees Fahrenheit, by the end of the century. That is expected to boost the emission of carbon compounds from soils.
The upper 3 meters -- about 10 feet -- of permafrost stores 1.9 trillion tons of carbon, more than double the amount in the atmosphere today, according to a recent study in the journal Bioscience.
"We are seeing thawing down to 5 meters," says geophysicist Vladimir Romanovsky of the University of Alaska. "A third to a half of permafrost is already within a degree to a degree and a half [Celsius] of thawing."
If only 1% of permafrost carbon were to be released each year, that could double the globe's annual carbon emissions, Romanovsky notes. "We are at a tipping point for positive feedback," he warns, referring to a process in which warming spurs emissions, which in turn generate more heat, in an uncontrollable cycle.
It's that positive feedback potential that's so terrifying. Sometimes I like to reassure myself by thinking, well, global warming may leave civilization a crippled wreck, but it's not as af if it will lead to the end of life as we know it. But do we know that for sure? Do we have any sort of grasp on what the upper bound of global warming effects might be? These sorts of positive feedbacks (and there are others, such as the possibility of the Amazon turning into a tinderbox) suggest the possibility that there may be a tipping point beyond which our ability to counter climate change will have evaporated. And no one knows when that day might come.