Says Aunty. And the Graun says “Arctic thawing could cost the world $60tn, scientists say”. $60tn is a big number. But lets not trouble ourselves with the popular press: lets go straight to the source, which is Nature (“Vast costs of Arctic change”, by Gail Whiteman, Chris Hope and Peter Wadhams). Is that an impeccable source? Weeell, not quite. Nature whores after big-impact studies in a rather regrettable way, and more importantly this is but a “Comment” not (as far as I can tell) a proper peer-reviewed article.
You’d certainly hope it wasn’t peer reviewed, because some of it is dodgy, most obviously the opening paragraph:
Unlike the loss of sea ice, the vulnerability of polar bears and the rising human population, the economic impacts of a warming Arctic are being ignored.
But lets skip over that (and that Wadhams has form with AMEG), and proceed to the meat of the comment, which proves to be remarkably brief: all they’ve done is plug in a 50 GT methane “burp” into an integrated assessment model and read off the predicted damages. This is something that anyone could do, with no special insight required.
The first Key Point is: is 50 Gt believable? Wiki tells me that annual methane emissions from natural+anthro is about 600 Tg, which is 0.6 Gt by my calculation; so WHW’s 50 Gt is close to 100 years emissions. So its a large number. I’ll come back to that, because I’ve realised I want to pause to put $60 tn in context, which is the second Key Point. As the article says:
This will lead to an extra $60 trillion (net present value) of mean climate-change impacts for the scenario with no mitigation, or 15% of the mean total predicted cost of climate change impacts (about $400 trillion).
So yes its a big number but its “only” a 15% increase on what you’d get anyway. Also, I think (though I’m open to correction on this) that “net present value” means all future impacts, back-calculated to today using discount rates. As the comment puts it, that can be compared to “the size of the world economy in 2012 (about $70 trillion)”. Or put another way, all future impacts of this methane release can be paid for by a single year’s economic output. Which discount rates? Probably Stern-style very low ones, guessing from the Graun stating that WHW are “using the Stern review”. And my recollection is that while the Stern-type numbers are indeed very large, the damages (from GW, and out to 2100 at least) are smaller than the benefits (that we get, economically, from emitting the CO2; I don’t mean that the benefits of GW outweigh its costs). So given the vast uncertainties in the Stern-style process (you can certainly change Stern’s numbers by more than 15% just by tweaking his discount rates a bit) I don’t think an extra 15% is news, ter be ‘onest.
Now, how about that 50 Gt. Wiki tells me that there are 1,400 Gt potentially going; so 50 is only a small fraction of that. Lets have the whole para, since its quite informative:
Current methane release has previously been estimated at 0.5 Mt per year. Shakhova et al. (2008) estimate that not less than 1,400 Gt of Carbon is presently locked up as methane and methane hydrates under the Arctic submarine permafrost, and 5-10% of that area is subject to puncturing by open taliks. They conclude that “release of up to 50 Gt of predicted amount of hydrate storage [is] highly possible for abrupt release at any time”. That would increase the methane content of the planet’s atmosphere by a factor of twelve.
13 is only an abstract, ending:
The total value of ESS [East Siberian Shelf] carbon pool is, thus, not less than 1,400 Gt of carbon. Since the area of geological disjunctives (fault zones, tectonically and seismically active areas) within the Siberian Arctic shelf composes not less than 1-2% of the total area and area of open taliks (area of melt through permafrost), acting as a pathway for methane escape within the Siberian Arctic shelf reaches up to 5-10% of the total area, we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. That may cause ∼12-times increase of modern atmospheric methane burden with consequent catastrophic greenhouse warming
But read that again carefully, noting fault zones, tectonically and seismically active areas. They aren’t (as I read it) saying that the 50 Gt will or might be released due to human activity; they’re saying that geologic events, and leaks through existing holes in the permafrost, might lead to this release. At least I think that’s what they’re saying. In which case its an odd calculation, because they appear to be assuming that all the faults will become active at once. Aren’t they? And my reading of it completely decouples it from GW. So I don’t understand.
WHW don’t ref that abstract, of course. Instead they ref Predicted methane emission on the East Siberian shelf by the same lead author (Shakhova), but this time in a proper journal. Or… is it? the journal is “Doklady Earth Science” which is a journal of the Presidium of the Russian Academy of Sciences. It contains English translations of papers published in Doklady Akademii Nauk (Proceedings of the Russian Academy of Sciences). Is it any good? I don’t know. I can only preview the first two pages of the paper and it looks suspiciously to me as though they are rather more assuming their emission rates than predicting them. Anyone who has access to the full journal, do let me know.
* It looks like the Graun has a rather worse take available, which mixes in implausibly early sea ice collapse: “Ice-free Arctic in two years heralds methane catastrophe – scientist”. Gavin isn’t impressed (detail) though as far as I can see, he’s only unimpressed by the sea ice collapse bit. Elsetweet, Gavin also says “nowhere is the v. low plausibility of emission pulse discussed” but since twitter is a pile of dingo’s kidneys I can’t work out how to link to it.
* Good heavens, this is unprecedented. one of the comments at the Graun is sane.
* Ruppel, C. D. (2011) Methane Hydrates and Contemporary Climate Change. Nature Education Knowledge 3(10):29
* A couple of posts on SS by Andy Skuce.
* Methane mischief: misleading commentary published in Nature by Jason Samenow, WaPo; Wadhams replies but continues to not-impress. As Gavin says, “Eemian”.
* Toward Improved Discussions of Methane & Climate
* Nafeez for the Record at P3
* Arctic and American Methane in Context – RC