WASHINGTON — 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.

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. And 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 doesn’t 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 tons – which is a vast amount and around double what currently exists in the atmosphere.

The new study comes to a broadly consistent conclusion. It finds that there are between 1,330 and 1,580 gigatons of carbon in the top 3 meters 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” – not to mention a simply unknown amount in permafrost below the sea in shallow continental shelves, such as beneath the East Siberian Sea.

Fortunately, the new study also finds that any sudden or catastrophic release of Arctic carbon stores is unlikely.

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