Based on a series of expeditions to the margins of the Arctic Ocean by ship and helicopter, University of Alaska researcher Natalia Shakhova and her colleagues report that methane, a greenhouse gas that is 30 times more effective in trapping heat in the atmosphere than carbon dioxide, is bubbling up from the continental shelf and leaking into the atmosphere. The estimated total: 8 teragrams — that's 8 trillion grams — per year. (See pictures of the effects of global warming.)
Exactly what this means for climate change, however, isn't at all certain. Eight teragrams of anything, let alone a heat-trapping greenhouse gas, sounds dangerous, but as Martin Heimann of the Max Planck Institute for Biogeochemistry in Jena, Germany, points out, the newly discovered methane leak represents a small piece of the overall global total of methane emissions — about 500 teragrams annually — from wetlands, termites and agriculture (including belching cows, rotting manure and rice paddies).
The number itself isn't what worries people, though: it's whether this newly identified methane source is part of an ominous trend. Climate scientists have long worried about the enormous amount of methane locked in Arctic permafrost, the thick layer of soil just beneath the surface that remains frozen all year. The methane was originally deposited there through decomposition of organic matter in ancient wetlands, and as long as it stays put, it can't contribute to climate change.
But as the planet warms and the permafrost thaws, methane could begin to escape into the atmosphere, where it would trap more heat and melt more permafrost — one of the many positive feedback mechanisms that could accelerate the climate change that is already under way.
The methane question is something readers of this blog will know that I am keeping a wary eye on. I'm glad that the amount of methane that these researchers measured doesn't amount to much in relation to the global methane budget. But reading an article like this worries me in a big big way -- are we just now starting to detect the tip of the iceberg of the methane time bomb starting to go off? I sure hope not...