What is methane hydrate?no_redirect=1

That second reason is half of the problem. Methane is a natural byproduct of decomposition. In other words, as plant material breaks down, it releases methane gas. (This is one reason why landfills have vents — to keep methane created by decomposing waste from building up underground.) As the Arctic warms, the ground, much of which normally stays frozen year-round due to the cold, will begin to thaw. Plants that were frozen a long time ago will begin to decompose, releasing methane gas. And: methane already trapped in the ground will no longer be frozen in place. It too will escape into the atmosphere.

The other half of the problem is from something called "methane hydrates." Methane hydrates are sort of like little ice cubes filled with methane bubbles. There are big methane hydrate deposits around the world, including off the shore of South Carolina. As the ocean warms, those ice cubes melt, and the methane bubbles up through the water and escapes into the air. That release is potentially even more problematic. As Nature notes, the release will happen "either steadily over 50 years or suddenly." The "suddenly" option would be very bad news.

Because the cost doesn't stem from the release of methane. The cost, that $60 trillion-plus price tag, is the result of the warming that accompanies the greenhouse gas production. The journal provided the graph at left which shows how increased methane release (from hydrates and permafrost melt) will cause temperatures to increase as well. More insulation means more warmth; a sudden increase in insulation from hydrate melt may mean a sudden spike in temperature. (Update: Other scientists think this sudden spike is unlikely.)

That warming will be costly. It means more precipitation, more floods, more drought, and, as New York City saw last year, higher seas. A study released earlier this month suggested that the oceans will rise an additional 2.3 meters for every degree Celsius the temperature increases. If the temperature goes up two degrees by 2035, under the worst-case scenario at left? That's 15 feet — higher than the highest point of flooding in lower Manhattan during Hurricane Sandy.

And it gets worse. Scientists have long worried about the "negative feedback loop" of a warming Arctic. The faster the Arctic warms, the faster it releases methane, which warms the atmosphere faster, which warms the Arctic faster. And not just the Arctic, of course — the amount of methane released from melt in the Antarctic could be just as large.

The icing on the cake? The melt of ice in the Arctic — which, despite North-Pole-pond weirdness, is not quite as severe as last year — means the loss of a large, white surface. Likewise the melt of on-land snow. With less white covering the globe, less sunlight will be reflected back upward. Remember how they used to teach you in elementary school that wearing a dark shirt on a sunny day would make you feel hotter? The Earth's white tank top is going to melt, leaving its dark blue or green skin exposed. Not convinced? A study last year found that soot from airplane exhaust that fell on Arctic snow helped increase ice melt by darkening the surface.

Again: The study reported by Nature doesn't address any of that. It applied an economic model to a specific region likely to experience some of these effects, but only modeling part of what was expected. And that cost $60 trillion in mitigation. The actual cost once all of the unknown factors and long-term effects are included? Well, we'll probably find out.

Photo: Taxis flooded during Hurricane Sandy. (AP)

This article is from the archive of our partner The Wire.

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Philip Bump is a former politics writer for The Atlantic Wire.