Andrew Revkin has completed his methane trilogy. The final installment, "More Views on Climate Risk and Arctic Methane," like part two "Leaders of Arctic Methane Project Clarify Climate Concerns" could be taken as a debunking of his original post on the subject ("Methane Time Bomb in Arctic Seas – Apocalypse Not"). But I prefer to think of it as journalism (very good journalism, when all is said and done) in real time.
Revkin begins his journey with the piece in the Independent, which he (correctly) recognizes as overhyped. He thinks he already knows this is rubbish, based upon his reporting in 2010:
This all builds on what I was told in 2010, when I last visited the question of methane releases from Arctic seas. . . . I urge you to read, and pass around, the 2010 post — “The Heat Over Bubbling Arctic Methane.”He talks to a couple of scientists, and gets a couple of quotes bolstering his view that nothing can have changed:
To review, the authors confirm “drastic bottom layer heating over the coastal zone” that they attribute to warming of the Arctic atmosphere, but conclude that “recent climate change cannot produce an immediate response in sub-sea permafrost.” That’s the understatement of the year considering their conclusion that even under sustained heating, the brunt of the sub-sea methane won’t be affected in this millennium.We of course do not need the brunt of it, but only, say 2% of it, to radically transform the world(1). No matter. Onward to the "publish" button!
Yet, he cannot have been without the nagging feeling that he forgot something. Something kind of important. Something like talking to the scientists being debunked. But they were on vacation! (2)
So, to his credit, he does a follow-up to that post when Natalia Shakhova and Igor Semiletov check in. And Revkin is no Michael Bay; his sequels are all better than the original. In part two, we find that these researchers were not panicky about methane plumes, as the Independent made them sound, be had real and legitimate concerns about the accuracy of the models Revkin spent his first post praising:
The obvious thing to do after this bombshell was to talk to even more scientists, which Revkin has now done. While none of them look like retreating to a compound in the Rockies just yet, no one appears quite as sanguine as the December 14 Revkin of "Apocalypse Not":
Yes, modeling is important. However, we know that modeling results cannot prove or disprove real observations because modeling always assumes significant simplification and should be validated with observational data, not vice versa. Much of our work includes this field validation. Last spring, we extracted a 53-meter long core sample from the East Siberian Arctic Shelf, to validate our conclusions about the current state of subsea permafrost. We found that the temperatures of the sediments were from 1.2 to 0.6 degrees below zero, Celsius, yet they were completely thawed. The model in the Dmitrenko paper [link] assumed a thaw point of zero degrees. Our observations show that the cornerstone assumption taken in their modeling was wrong.
Raymond T. Pierrehumbert: But the clathrate release problem is in a rather different category from the runaway greenhouse issue. It has to be seen as just one of the many fast or slow carbon catastrophes possibly awaiting us, in a system we are just groping to understand. The models of destabilization are largely based on variants of diffusive heat transport, but the state of understanding of slope avalanches and other more exotic release mechanisms is rather poor — and even if it turns out that rapid methane degassing isn’t in the cards, you still do have to worry about those several trillion metric tons of near-surface carbon and how secure they are. It’s like worrying about the state of security of Soviet nuclear warheads, but where you have no idea what kind of terrorists there might be out there and what their capabilities are — and on what time scales they operate.
Edward Brook: One problem with this discussion is that there is no definition of “time bomb” so people get confused. It seems quite likely that continued global warming will increase the emissions of methane from permafrost deposits and marine hydrates. Some of that will get in to the atmosphere, though … some will also be consumed in the water column and in soils. This “chronic” source may increase over time, and affect climate, but for the reasons you discussed it is likely to be slow, and not a catastrophic risk. [So we can't say there's nothing to worry about for a millennium?] Of course it is still important.He goes on to quote a few other scientists to the effect that yes, methyl hydrates may contribute to climate change as a feedback, but no, massive near-instantaneous releases don't seem very likely. Which is comforting, of course, but only up to a point. Besides the fact that they could be wrong (and we know that climate science is not at its best when predicting when stuff is gonna melt) even if they are spot on, how gradual are we talking? Suppose a linear release over a thousands years -- 0.1% per year. That's 1.7 Gt of methane -- roughly half the amount of methane in the atmosphere today. Even if half of it were oxidized in the water column, you would still double the amount of methane in the atmosphere in four years and increase it by a factor of ten in fairly short order. Sweet dreams.
I can't judge Andrew Revkin harshly in this. It's impossible for me to dislike the man (how could I -- he left a comment on my blog!) The worst thing you can say about him is, he's a blogger. He's quick off the draw. Sometimes he'll print first and collect more facts afterwards. He has hobbyhorses and is the more likely to launch into debate to defend positions he's staked out before. But he will keep eleborating, keep talking to people, and correct his original views where they were excessive or misinformed (though you still need to change the date of publication (Oct 19, not Dec 6) in your original post, Andy!) What can I say to that, without being a hypocrite? Let he who has never done a quick edit after reading comments, cast the first stone.
1) 2% of 1700Gt = 34Gt, increasing the existing methane burden in the atmosphere by a factor of tem, with a change in forcing of about +4W/m^2. Given that such a release over a short time period would overwhelm the supply of reactive species to break it down, despite methane's normally short life in the atmosphere, you'd probably be looking at a good 30 years of that before it even began to wane.
2) If I had ever made that excuse to an editor of mine, they would have fried me in extra virgin olive oil and served me with a light white sauce. Especially if I included nothing in the piece to the effect that "I tried to contact these people, but I couldn't reach them."