Thawing per­ma­frost could inject enough car­bon into the atmo­sphere to cook the planet. But nobody’s quite sure how fast it’s going to happen.

Permafrost is a giant cold-storage com­post heap, stuffed full of frozen car­bon. Just like you chucked out last night’s potato peel­ings, the planet has chucked out bil­lions of tonnes of dead plants, trees, mam­moths and, yes, polar bears, all of which is now hap­pily interred under the Arctic wastes.

The dif­fer­ence is that while your com­post heap ticks over at a nice warm tem­per­at­ure, break­ing down the potato peel­ings into com­post, the frozen ground which makes up per­ma­frost stops that organic stew of Arctic flora and fauna from decom­pos­ing, safely lock­ing up the car­bon stored in it.

I say ‘safely lock­ing up’ because from the point of view of cre­at­ing human civil­isa­tion, per­ma­frost has been pretty handy. While the per­ma­frost has been per­man­ently frozen, we’ve been busy eke­ing out human life, dis­cov­er­ing fire, devel­op­ing agri­cul­ture, grow­ing our pop­u­la­tion. While we’ve been busy nur­tur­ing the cap­ab­il­it­ies that ulti­mately allow the lucky few to par­ti­cip­ate in Britain’s Got Talent, the planet’s been watch­ing our backs by keep­ing this massive store of car­bon locked up under the frozen parts of the planet’s surface.

Of course, in these excit­ing cli­matic times, per­ma­frost is a pretty poor name. Because as the planet warms up, the per­ma­frost is no longer per­man­ent — it’s tak­ing on less of the char­ac­ter of a crisp winter’s day, and more of the char­ac­ter of a damp boggy field. Normally, every Arctic sum­mer the very top layer of per­ma­frost melts before refreez­ing in the winter. But as the planet warms, (and it’s warm­ing faster in the Arctic than any­where else), the melt is get­ting deeper and more wide­spread, and in some places the per­ma­frost isn’t refreez­ing com­pletely in winter.

When per­ma­frost melts, it releases either car­bon diox­ide or meth­ane into the atmo­sphere. Both are import­ant green­house gases. Both will speed up the rate at which the planet warms. And there’s a hell of a lot of car­bon stored in per­ma­frost. Maybe twice the amount that’s cur­rently in the atmo­sphere. Unlock that frozen store, the worry is, and we’re dab­bling with the pos­sib­il­ity of adding enough car­bon to the atmo­sphere to change the atmo­spheric era we’re in, to some­thing even more excit­ing than the Anthropocene, and by implic­a­tion, ser­i­ously jeapord­ising our abil­ity to watch Susan Boyle on you­tube.

That kinds of sug­gests a bit of a dooms­day scen­ario, or at least it does to envir­on­ment journ­al­ists. But per­ma­frost is a great example of the dif­fi­culties there are in restrain­ing our desire for clear cut state­ments about how the climate’s going to behave as the planet warms (and to a cer­tain extent, the media’s desire for scream­ing head­lines about the end of the world), with the cau­tious nature of the sci­entific field.

Permafrost is a great example of the dif­fi­culties there are in restrain­ing our desire for clear cut state­ments about how the climate’s going to behave as the planet warms with the cau­tious nature of the sci­entific field.

Talk to cli­mate sci­ent­ists who work on per­ma­frost and they’re pretty tent­at­ive about the con­clu­sions of their work. It’s a chal­len­ging field to make pre­dic­tions in at the moment, because there don’t yet exist good, widely accep­ted mod­els of per­ma­frost melt (we’re prob­ably at least a few years away from that), and sci­ent­ists rely on a pretty small num­ber of field research­ers who ardu­ously travel around Siberia and Alaska tak­ing point-by-point site meas­ure­ments of gas emis­sions, which is a pretty crude way to pre­dict emis­sions on such a huge scale.

Only very recently are we begin­ning to get pre­dic­tions about how much per­ma­frost melt might con­trib­ute to green­house gas emis­sions. Edward Schurr, a good name to look out for if you’re inter­ested in read­ing more, recently wrote a paper in Nature broadly sug­gest­ing that per­ma­frost emis­sions might reach in the order of a giga­tonne a year — and over a few dec­ades per­ma­frost could be a ‘large’ car­bon source in a warmer world.  But these are still early results.

What can we say con­fid­ently? We can cer­tainly say that per­ma­frost rep­res­ents a source of car­bon emis­sions that are addi­tional to what the IPCC has con­sidered up to this point. The IPCC’s latest treat­ment of per­ma­frost didn’t attempt to include any assess­ment of per­ma­frost as a car­bon source — they were only inter­ested in talk­ing about the effect large parts of the Arctic land sur­face col­lapsing might have on stuff that had been built there — houses, gas pipelines, nuc­lear react­ors, that kind of thing. Not unim­port­ant, and in one way you want to cut them some slack for not con­sid­er­ing it, because they’re not really cut out for apprais­ing rap­idly chan­ging recent science.

In another way, though, it makes you want to bang your head against a table — because in emis­sions terms we’re already track­ing along the worst-case emis­sions scen­arios from the stuff the IPCC did con­sider, even without the pos­sib­il­ity of the north of the planet out­gass­ing car­bon diox­ide and meth­ane like a com­post heap hav­ing a psychotic breakdown.

There is one way in which per­ma­frost is really inter­est­ing. A com­mon cri­tique of envir­on­ment­al­ists is that they advoc­ate the ‘pre­cau­tion­ary prin­ciple’ — which says we should do more rather than less to tackle cli­mate change, just in case – without good reason. But the cur­rent level of know­ledge we have about per­ma­frost is a pretty clear-cut example of why the pre­cau­tion­ary prin­ciple is actu­ally a per­fectly reas­on­able way to go about things.

Because: we can def­in­itely say per­ma­frost emis­sions will be addi­tional to the IPCC SRES scen­arios, and we can def­in­itely say that they’ve got the poten­tial to be huge, but we can’t (yet) say how much CO2 and meth­ane is actu­ally going up into the atmo­sphere, and we can’t (yet) say how quickly emis­sions are going to increase. What do you do in that situ­ation? Ignore it, as the IPCC were forced to?  Or maybe add a bit of a safety mar­gin to the sys­tem by being ambi­tious? Our under­stand­ing of the sci­ence of per­ma­frost thaw is a great advert for the pre­cau­tion­ary principle.

Permafrost is not a clear-cut situ­ation. It’s also one we don’t under­stand par­tic­u­larly well, yet. But by see­ing that it can only really speed up the rate at which the planet changes, we see a clear argu­ment for not devel­op­ing that under­stand­ing by actu­ally melt­ing the stuff.