AN EXCHANGE ON TWITTER
In the Guardian, Nafeez Ahmed raises seven points in defense of the Shakhova hypothesis advanced as “likely” by Whiteman, Hope and Wadhams in a notorious Nature comment, and criticized here and elsewhere.
Specifically, Mr. Ahmed writes in response to Chris Colose’s thorough and meticulous analysis of Shakhova’s excessive claims.
I had an interesting Twitter exchange with Ahmed, which contains the following messages:
me: @NafeezAhmed no the ESAS “methane bomb” event is as close to impossible as anything in earth science can be; actual geophysics refutes it.
NA: .@mtobis lol, really? I guess that’s y major scientific review of the issue in Review of Geophysics says catastrophic methane rls plausible
me: @NafeezAhmed ref pls? I believe you may be conflating issues.
NA: Ref is linked here http://www.theguardian.com/environment/earth-insight/2013/aug/05/7-facts-need-to-know-arctic-methane-time-bomb …
me: @NafeezAhmed If you think “carbon releases from Arctic permafrost …between 50-100 Gt this century” supports Shakhova you need a new beat.
and (perhaps more agressively than was warranted) me: @NafeezAhmed illustrates my claim that science matters and that very few non-scientist journalists can report on science effectively.
so I softened it with me: I’m sure you are a nice guy and I share your view that I’m a nasty old SOB. But I’m right on this, and you aren’t.
This exchange went on further, quite a bit longer than a Twitter conversation comfortably supports. Twitter is no place to hash these sorts of things out. As everyone was getting frustrated, Nafeez Ahmed ended:
NA: @CColose @Perwis @PeterGleick @IdiotTracker @mtobis so wiil wait 4 critique response showing my 7 facts r factoids
And given that Mr. Ahmed has a prominent platform, he is indeed due this much.
IN DEFENSE OF MY SNARK
Before I take on his 7 points in detail let me defend my snark.
Ahmed refers in the Twitter exchange to a paper in Rev Geophys, suggesting that Arctic thawing may release in excess of 50 GT of C, a very serious matter, amounting to something like 10% of our remaining margin to a best-guess warming around the best-guess dangerous threshhold of 2 C. This is in keeping with my prior understanding, and make no mistake, it is very bad news – it amounts to more than 50 billion tons MORE of fossil fuel that needs to be left in the ground for a given level of damage.
But Ahmed refers to the paper in support of a very different assertion, that 50 GT of methane would be released. It’s commonly assumed as a rule of thumb that an abrupt methane release is from 20 to 70 times worse per molecule than the same amount of carbon released as CO2. So if true this would be very serious business indeed. 50 billion tons of methane would plausibly be civilization-ending and a massive extinction event. But the paper to which he points triumphantly says nothing of the sort.
So I conclude that he doesn’t really know what he is talking about. Specifically he has already shown that he is confused about the distinction between methane releases and CO2 releases, something that someone on the climate beat ought to be clear about.
THE MAIN ISSUE WITH THE CLATHRATE BOMB SCENARIO
The fact that there’s a lot of methane under the sea floor is not in dispute. The question is whether there is a way to destabilize a whole lot of it at once.
In order to justify this, Shakhova points to a possibility that some clathrates remain in the frozen phase even though they are at an unstable depth. This can occur if they are encased in water ice. A few nodules of this configuration have been identified, ironically because they are a threat to oil rigs, but they have NEVER been observed in the East Siberian sea, and it’s a long way from a few ounces to fifty billion tons. If fifty billion tons of the stuff were distributed just below the sea floor, the scenario proposed would not be wholly implausible. But there is no evidence of anything remotely like that, and no mechanism whereby it might exist.
Anything which does not directly defend the existence of a large deposit of clathrates existing for millennia at pressures where they ought to have long since disintegrated is not a serious defense of the clathrate bomb scenario. And none of Ahmed’s points address this.
THE SEVEN POINTS
Most of the seven points betray fundamental confusion about clathrates. The lay reader should not be expected to understand these a priori; it is the reporter’s job to elucidate them. But to do so, the reporter has to gain some understanding of the material. Sadly, Ahmed betrays little understanding, though he does have the wit to troll the literature for items which superficially support his unease about methane.
1. The 50 Gigatonne decadal methane pulse scenario was posited by four Arctic specialists, and is considered plausible by Met Office scientists
Whether we should be acknowledging the “Arctic specialists” as actually expert is, frankly, the question at hand.
So what about “is considered plausible by Met Office scientists”? This was exactly the point of contention on Twitter. Ahmed has conflated CO2 and methane.
VERDICT: conflation and confusion
2. Arctic methane hydrates are becoming increasingly unstable in the context of anthropogenic climate change and it’s impact on diminishing sea ice
In support, aside from an article in EOS (more a newsmagazine for scientists than a journal) we see a quote from a peer reviewed journal:
“… causing the liberation of methane from decomposing hydrate… If this process becomes widespread along Arctic continental margins, tens of Teragrams of methane per year could be released into the ocean.”
But tens of teragrams is about two orders of magnitude too low to make a difference.
Further, as evidence that the emissions are a consequence of recent climate change rather than part of the background climate, Ahmed offers:
“… has led about 10 expeditions in the Laptev Sea but during the 1990s he did not detect any elevated levels of methane. However, since 2003 he reported a rising number of methane ‘hotspots’, which have now been confirmed using more sensitive instruments.”
Identifying the clear fallacy here is left as an exercise for the reader.
VERDICT: obscure references, confusion about quantities, unwarranted extrapolation
3. Multiple scientific reviews, including one by over 20 Arctic specialists, confirm decadal catastrophic Arctic methane release is plausible
A couple of reviews do give some support to this, but are vague about time scales. The DOE report specifically says:
“The time scales for destabilization of marine hydrates are not well understood and are likely to be very long for hydrates found in deep sediments but much shorter for hydrates below shallow waters, such as in the Arctic Ocean… Overall, uncertainties are large, and it is difficult to be conclusive about the time scales and magnitudes of methane feedbacks, but significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out… The risk of a rapid increase in [methane] emissions is real but remains largely unquantified.”
To emphasize: “The risk of a rapid increase in [methane] emissions is real but remains largely unquantified.”
There is a very wide gap between a rapid increase (which, again, everybody believes possible) and the 50 GT CH4 scenario, because the current release is orders of magnitude less than gigatons per year. That leaves plenty of room for acceleration without hitting the cataclysmic level. Further, this evidence doesn’t support the immediacy of that scenario at all.
VERDICT: While this is the best supported of the seven points, it is far from rising to the occasion on quantities or time scales, and does not in any way support the idea of a large deposit of unstable clathrates near the sea floor.
4. Current Arctic methane levels are unprecedented
Yes, they are at the high end of the instrumental record, but they are not climbing rapidly.
Despite NOAA scientist Dr Dlugokencky‘s reassurances that current Arctic methane emission levels are nothing to be “alarmed” about, his own data shows that Arctic methane levels were 1850 ppb in yr 2000, rising up to 1890 ppb in 2012.
Oh please, this is just silly. A 2 % increase in 12 years, assuming it’s not just measurement noise or random variation,will not get us to a ten thousand per cent increase very quickly.
5. The tipping point for continuous Siberian permafrost thaw could be as low as 1.5C
In support of this:
New research led by Prof Antony Vaks published this year in Science analysing a 500,000 year history of Siberian permafrost found that “global climates only slightly warmer than today are sufficient to thaw significant regions of permafrost.” The study by eight experts found that there is a tipping point for continuous thawing of permafrost at 1.5C which “can potentially lead to substantial release of carbon trapped in the permafrost into the atmosphere.”
Yes, this is definitely on the table. Unfortunately, it has nothing to do with undersea methane.
VERDICT: Confusion and conflation again.
6. Arctic conditions during the Eemian interglacial lasting from 130,000 to 115,000 years ago are a terrible analogy for today’s Arctic
This is plausible as it stands, but as a response to Chris Colose it is terrible, because Colose is not relying on the Eemian but on the early Holocene as the analogous period. So the refutation is strictly a strawman.
This is backed up by a meandering quote from “Prof” Paul Beckwith, the “Professor Beckwith” who is a grad student at Ottawa U. The one who predicted in May of this year that all the Arctic sea ice would vanish this year. He is a gloomy Gus indeed, but his track record isn’t all that impressive.
VERDICT: straw man
7.Paleoclimate records will not necessarily capture a large, abrupt methane pulse
Now, we swing back to saying that it HAS occurred in the recent geological past, indeed at the time which Colose says is the better analogy. In evidence (evidence which in point 6 were implied to be nonexistent) there is a paper referring specifically to a biotic feedback, and NOT clathrate-related.
VERDICT: self-contradiction, confusion and conflation
PANTS ON FIRE
I am pleased to report, based on knowledge which by happenstance I had before the current controversy, that the specific mechanism Shakhova threatens us with is implausible in the extreme. I am pleased to report that no plausible different mechanism which could rapidly release this enormous quantity of methane has been proposed either. I base the second claim on the fact that people have been casting about for one, and in the end not come up with any.
There is a serious caveat that 50 GT or more of carbon dioxide (CO2) (as opposed to methane (CH4)) may well be released as a consequence of Arctic thawing. CO2 is, though much more common and much longer-lived in the system, less dangerous by weight than methane. But 50 GT is a very large quantity even of CO2. As such, it is a big enough and uncertain enough term that it is a real threat. But it is not a guaranteed catastrophe like the Shakhova hypothesis, and not relevant to it. That Ahmed repeatedly refers to it interchangeably with the Shakhova scenario is telling.
SCIENTIFIC CONSENSUS HAS BEEN REACHED
* Gavin Schmidt has been quoted saying “The scenario they used is so unlikely as to be completely pointless talking about,”"
* In the same article, David Archer, a coauthor of the first papers on the global clathrate inventory, is more subdued but argues in the same direction:
“It’s weird for me to be saying, ‘Oh, it could never happen.’ It’s always the wrong side of things when you’re talking about nature,” says David Archer of the Arctic methane catastrophe scenario. “But,” he adds, “nobody’s come up with a defendable way of it happening all at once.”
* Chris Colose:
“I’ve seen the Guardian’s most recent response. I still think it conflates many different issues, including varying sources of CH4 releases (e.g., in his point #7, the 2009 Science paper he references with respect to the Younger Dryas are talking about wetlands, not hydrate destabilization), and still presents no evidence for a significantly new Arctic methane source to the atmosphere….again, observed methane emissions around the Arctic are not evidence that they are a new source. The point #4 about highest CH4 levels in 800k is due to direc anthropogenic activity, not hydrate destabilization, and renewed growtth in atmospheric CH4 has been attributed to a few different factors (Dlugokencky has recent literature on this). If a positive hydrate feedback exists, it is currently very small and not emerging clearly.”
* Andy Skuce:
“None of the references in the Guardian article point to observations of shallow gas hydrates on the ESAS. There are shallow gas hydrates (around 60 metres depth) reported in Yamal, some 2000 km away, but those are (according to the author) relict hydrates thought to have been formed when that area was overlaid by an icesheet (or a marine transgression) and have been preserved in a metastable form after disappearence of the icesheet (or regression of the sea). As far as I know, nobody has proposed those kinds of events in this part of eastern Siberia. On the contrary, the local sea level on the ESAS has risen since the last glacial maximum, submerging the permafrost that formed when the shelf was exposed land.
“All of the references cited show that hydrates form below 200 metres depth in areas of permafrost. The Shakhova et al 2010 paper does not present any geophysical or sampling evidence for hydrates above 200m on the ESAS. Permafrost, yes, gas leaks yes, but not shallow hydrates.”
* in short, Gavin Schmidt again:
“There is still no evidence of actual (thermodynamically unstable) shallow hydrates on ESAS. Sorry, but I’m not buying it.”
* A comment by Nisbet et al is being submitted to Nature
Clearly large individual events can and probably will occur in the near future, such as major pockmark bursts and perhaps massive submarine landslides on hydrate, while local bubbling may be widespread on shelf seas. But even with such events the geological record shows that the total decadal hydrate-sourced methane reaching the atmosphere is very unlikely to exceed 1 Gt, and may be far less than that. After millennia of cold, Late Glacial hydrates were probably more abundant and more rapidly destabilized by marine transgression and warming than will be the case in the current rapid Arctic warming. A 50 Gt decadal release, at a rate ~100x greater that during glacial/postglacial transitions, is thus improbably large.
WHY DOES THIS MATTER
For those of us trying to cope with public denial, this offers us a case that we can study without having our usual frustrations color our judgment. There is no better way to understand the creation of zombie pseudo-facts among the opponents of climate policy than to see an instance among its supporters.
The key question is why Ahmed is clinging to his illusion about what science says quite so steadfastly. A follow-up essay will relate this to the question of “postnormal”, i.e., politically salient science. Science as normally practiced quietly ignores unsupportable arguments. Political commentary picks them up with a vengeance. In practice we end up with one reasonably harmonious scientific community which makes ordinary progress in the ordinary way, and a public which perceives fringe players as key, and two competing communities at war over a contested hypothesis.
We need journalists who have the ability to make actual judgments. Difference splitting is not the only way to get this wrong. Aligning with a political position and judging evidence on its congruence with that politics is another. There is false symmetry about science, but it results from a real symmetry about political reporting which is indifferent to balancing evidence.
I have no opinions about Nafeez Ahmed outside this incident. In this case he has bet on the wrong horse. This is not without precedent, and people make mistakes. But the tenacity and relative incoherence of his defense is harder to forgive.
UPDATE 2: UPDATE: Nafeez has withdrawn his support for the Shakhova scenario. I have verified that it is him via his Twitter account.