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As permafrost thaws, Arctic couldbe big major carbon emitter, study says

PUBLISHED : Sunday, 12 April, 2015, 8:29am
UPDATED : Thursday, 16 April, 2015, 10:19am
TNS

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As the frozen Arctic soil known as "permafrost" thaws, it could release large amounts of carbon - in the form of both carbon dioxide and methane - to the atmosphere. And this new source of greenhouse gas emissions could be large enough that it could substantially undermine attempts to cut down on emissions from fossil fuels.

Now, an overview of what we know about the permafrost carbon problem has just come out in Nature, written by a group of 17 experts on the matter. In other words, this is probably the most thorough scientific look at the issue yet. The researchers, led by Edward Schuur, of Northern Arizona University, basically confirm that we have a serious problem - if not necessarily a catastrophe - on our hands.

The bottom line is that the permafrost carbon problem does not look like it's going to just go away as researchers better refine their estimates. Rather, it's something that the world, and especially its leaders who are the ones making climate agreements, will have to deal with.

"Initial estimates of greenhouse gas release point towards the potential for substantial emissions of carbon from permafrost in a warmer world, but these could still be underestimates," the study notes.

A much cited estimate from past literature is that northern permafrost contains 1,700 gigatons of carbon - a gigaton is a billion metric tonnes - which is a vast amount and around double what exists in the atmosphere.

The new study goes back closely over past estimates in light of new evidence, and comes to a broadly consistent conclusion. It finds that there are between 1,330 and 1,580 gigatons of carbon in the top three metres of global permafrost soil, in what are called yedomas (permafrost with particularly high ice content), and in Arctic river deltas.

And then on top of that, it says, there is a possible 400 additional gigatons in "deep terrestrial permafrost sediments". Overall, it's a troubling large amount of carbon - especially in light of numbers presented by the UN Intergovernmental Panel on Climate Change, suggesting that if we want to have a good chance of holding global warming to 2 degrees Celsius above pre-industrial temperatures, we probably have only about 500 more gigatons of carbon that we can emit.

"We've gone back with this whole synthesis effort, looked through all the data, and synthesized, and yeah, this problem is not going away," says lead study author Schuur.

The good news is that the permafrost emissions are "unlikely to occur at a speed that could cause abrupt climate change over a period of a few years to a decade", as the study puts it. The bad news, though, is that 160 gigatons, even though it is less than we are expected to emit from fossil fuels in coming decades, is still a large enough amount to really matter for the planet - especially given the relatively tight carbon budget that we have remaining.