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Arctic and American Methane in Context

Filed under: — david @ 24 November 2013

Lots of interesting methane papers this week. In Nature Geoscience, Shakhova et al (2013) have published a substantial new study of the methane cycle on the Siberian continental margin of the Arctic Ocean. This paper will get a lot of attention, because it follows by a few months a paper from last summer, Whiteman et al (2013), which claimed a strong (and expensive) potential impact from Arctic methane on near-term climate evolution. That economic modeling study was based on an Arctic methane release scenario proposed in an earlier paper by Shakhova (2010). In PNAS, Miller et al (2013) find that the United States may be emitting 50-70% more methane than we thought. So where does this leave us?

The Context

Because methane is mostly well-mixed in the atmosphere, emissions from the Arctic or from the US must be seen within the context of the global sources of methane to the atmosphere. Estimates of methane emissions from the Arctic have risen, from land (Walter et al 2006) as well now as from the continental shelf off Siberia. Call it 20-30 Tg CH4 per year from both sources. The US is apparently emitting more than we thought we were, maybe 30 Tg CH4 per year. But these fluxes are relatively small compared to the global emission rate of about 600 Tg CH4 per year. The Arctic and US anthropogenic are each about 5% of the total. Changes in the atmospheric concentration scale more-or-less with changes in the chronic emission flux, so unless these sources suddenly increase by an order of magnitude or more, they won’t dominate the atmospheric concentration of methane, or its climate impact.

American Methane Emissions Higher Than Previously Thought

Miller et al (2013) combine measurements of methane concentrations in various locations through time with model reconstructions of wind fields, and “invert” the information to estimate how much methane was released to the air as it blew over the land. This is a well-established methodology, pushed to constrain US anthropogenic emissions by including measurements from aircraft and communications towers in addition to the ever-invaluable NOAA flask sample network, and incorporating socioeconomic and industrial data. The US appears to be emitting 50-70% more methane than the EPA thought we were, based on “bottom up” accounting (adding up all the known sources).

Is this bad news for global warming?

Not really, because the one real hard fact that we know about atmospheric methane is that it’s concentration isn’t rising very quickly. Methane is a short-lived gas in the atmosphere, so to make it rise, the emission flux has to continually increase. This is in contrast to CO2, which accumulates in the atmosphere / ocean system, meaning that steady (non-rising) emissions still lead to a rising atmospheric concentration. There is enough uncertainty in the methane budget that tweaks of a few percent here and there don’t upset the apple cart. Since the methane concentration wasn’t rising all that much, its sources, uncertain as they are, have been mostly balanced by sinks, also uncertain. If anything, the paper is good news for people concerned about global warming, because it gives us something to fix.

Methane from the Siberian continental shelf

The Siberian continental shelf is huge, comprising about 20% of the global area of continental shelf. Sea level dropped during the last glacial maximum, but there was no ice sheet in Siberia, so the surface was exposed to the really cold atmosphere, and the ground froze to a depth of ~1.5 km. When sea level rose, the permafrost layer came under attack by the relatively warm ocean water. The submerged permafrost has been melting for millennia, but warming of the waters on the continental shelf could accelerate the melting. In equilibrium there should be no permafrost underneath the ocean, because the ocean is unfrozen, and the sediment gets warmer with depth below that (the geothermal temperature gradient).

Ingredients of Shakhova et al (2013)

  1. There are lots of bubbles containing mostly methane coming up from the shallow sea floor in the East Siberian Arctic shelf. Bubbles like this have been seen elsewhere, off Spitzbergen for example (Shakhova et al (2013)). Most of the seep sites in the Siberian margin are relatively low flow but a few of them are much larger.


  2. The bubbles mostly dissolve in the water column, but when the methane flux gets really high the bubbles rise faster and reach the atmosphere better. When methane dissolves in the water column, some of it escapes to the atmosphere by evaporation before it gets oxidized to CO2. Storms seem to pull methane out of the water column, enhancing what oceanographers call “gas exchange” by making waves with whitecaps. Melting sea ice will also increase methane escape to the atmosphere by gas exchange. However, the concentration of methane in the water column is low enough that even with storms the gas exchange flux seems like it must be negligible compared with the bubble flux. In their calculation of the methane flux to the atmosphere, Shakhova et al focused on bubbles.
  3. Sediments that got flooded by rising sea level thousands of years ago are warmer than sediments still exposed to the colder atmosphere, down to a depth of ~50 meters. This information is not directly applied to the question of incremental melting by warming waters in the short-term future.
  4. The study derives an estimate of a total methane emission rate from the East Siberian Arctic shelf area based on the statistics of a very large number of observed bubble seeps.

Is the methane flux from the Arctic accelerating?

Shakhova et al (2013) argue that bottom water temperatures are increasing more than had been recognized, in particular in near-coastal (shallow) waters. Sea ice cover has certainly been decreasing. These factors will no doubt lead to an increase in methane flux to the atmosphere, but the question is how strong this increase will be and how fast. I’m not aware of any direct observation of methane emission increase itself. The intensity of this response is pretty much the issue of the dispute about the Arctic methane bomb (below).

What about the extremely high methane concentrations measured in Arctic airmasses?

Shakhova et al (2013) show shipboard measurements of methane concentrations in the air above the ESAS that are almost twice as high as the global average (which is already twice as high as preindustrial). Aircraft measurements published last year also showed plumes of high methane concentration over the Arctic ocean (Kort et al 2012), especially in the surface boundary layer. It’s not easy to interpret boundary-layer methane concentrations quantitatively, however, because the concentration in that layer depends on the thickness of the boundary layer and how isolated it is from the air above it. Certainly high methane concentrations indicate emission fluxes, but it’s not straightforward to know how significant that flux is in the global budget.

The more easily interpretable measurement is the time-averaged difference between Northern and Southern hemisphere methane concentrations. If Arctic methane were driving a substantial increase in the global atmospheric methane concentration, it would be detectable in this time-mean interhemispheric gradient. Northern hemisphere concentrations are a bit higher than they are in the Southern hemisphere (here), but the magnitude of the difference is small enough to support the conclusion from the methane budget that tropical wetlands, which don’t generate much interhemispheric gradient, are a dominant natural source (Kirschke et al 2013).

What about methane hydrates?

There are three possible sources of the methane in the bubbles rising out of the Siberian margin continental shelf:

  1. Decomposition (fermentation) of thawing organic carbon deposited with loess (windblown glacial flour) when the sediment was exposed to the atmosphere by low sea level during the last glacial time. Organic carbon deposits (called Yedoma) are the best-documented carbon reservoir in play in the Arctic.
  2. Methane gas that has been trapped by ice, now escaping. Shakhova et al (2013) figure that flaws in the permafrost called taliks, resulting from geologic faults or long-running rivers, might allow gas to escape through what would otherwise be impermeable ice. If there were a gas pocket of 50 Gt, it could conceivably escape quickly as a seal breached, but given that global gas reserves come to ~250 Gt, a 50 Gt gas bubble near the surface would be very large and obvious. There could be 50 Gt of small, disseminated bubbles distributed throughout the sediment column of the ESAS, but in that case I’m not sure where the short time scale for getting the gas to move comes from. I would think the gas would dribble out over the millennia as the permafrost melts.
  3. Decomposition (melting) of methane hydrates, a peculiar form of water ice cages that form in the presence of, and trap, methane.

Methane hydrate seems menacing as a source of gas that can spring aggressively from the solid phase like pop rocks (carbonated candies). But hydrate doesn’t just explode as soon as it crosses a temperature boundary. It takes heat to convert hydrate into fluid + gas, what is called latent heat, just like regular water ice. There could be a lot of hydrate in Arctic sediments (it’s not real well known how much there is), but there is also lot of carbon as organic matter frozen in the permafrost. Their time scales for mobilization are not really all that different, so I personally don’t see hydrates as scarier than frozen organic matter. I think it just seems scarier.

The other thing about hydrate is that at any given temperature, a minimum pressure is required for hydrate to be stable. If there is pure gas phase present, the dissolved methane concentration in the pore water, from Henry’s law, scales with pressure. At 0 degrees C, you need a pressure equivalent to ~250 meters of water depth to get enough dissolved methane for hydrate to form.

The scariest parts of the Siberian margin are the shallow parts, because this is where methane bubbles from the sea floor might reach the surface, and this is where the warming trend is observed most strongly. But methane hydrate can only form hundreds of meters below the sea floor in that setting, so thermodynamically, hydrate is not expected to be found at or near the sea floor. (Methane hydrate can be found close to the sediment surface in deeper water depth settings, as for example in the Gulf of Mexico or the Nankai trough). The implication is that it will take centuries or longer before heat diffusion through that sediment column can reach and destabilize methane hydrates.

Is there any way nature might evade this thermodynamic imperative?

If hydrate exists in near-surface sediments of the Siberian margin, it would be called “metastable”. Metastability in nature is common when forming a new phase for which a “seed” or starting crystal is needed, like cloud droplets freezing in the upper atmosphere. But for decomposition to form water and gas one would not generally expect a barrier to just melting when energy is available. Chuvilin et al (2011) monitored melting hydrate in the laboratory and observed some quirkiness.


But these experiments spanned 100 hours, while the sediment column has been warming for thousands of years, so the experiments do not really address the question. I have to think that if there were some impervious-to-melting hydrate, why then would it suddenly melt, all at once, in a few years? Actual samples of hydrate collected from shallow sediments on the Siberian shelf would be much more convincing.

What about that Arctic methane bomb?

Shakhova et al (2013) did not find or claim to have found a 50 Gt C reservoir of methane ready to erupt in a few years. That claim, which is the basis of the Whiteman et al (2013) $60 trillion Arctic methane bomb paper, remains as unsubstantiated as ever. The Siberian Arctic, and the Americans, each emit a few percent of global emissions. Significant, but not bombs, more like large firecrackers.


  1. N. Shakhova, I. Semiletov, I. Leifer, V. Sergienko, A. Salyuk, D. Kosmach, D. Chernykh, C. Stubbs, D. Nicolsky, V. Tumskoy, and . Gustafsson, "Ebullition and storm-induced methane release from the East Siberian Arctic Shelf", Nature Geoscience, vol. 7, pp. 64-70, 2013.
  2. G. Whiteman, C. Hope, and P. Wadhams, "Vast costs of Arctic change", Nature, vol. 499, pp. 401-403, 2013.
  3. N.E. Shakhova, V.A. Alekseev, and I.P. Semiletov, "Predicted methane emission on the East Siberian shelf", Doklady Earth Sciences, vol. 430, pp. 190-193, 2010.
  4. S.M. Miller, S.C. Wofsy, A.M. Michalak, E.A. Kort, A.E. Andrews, S.C. Biraud, E.J. Dlugokencky, J. Eluszkiewicz, M.L. Fischer, G. Janssens-Maenhout, B.R. Miller, J.B. Miller, S.A. Montzka, T. Nehrkorn, and C. Sweeney, "Anthropogenic emissions of methane in the United States", Proceedings of the National Academy of Sciences, vol. 110, pp. 20018-20022, 2013.
  5. E.A. Kort, S.C. Wofsy, B.C. Daube, M. Diao, J.W. Elkins, R.S. Gao, E.J. Hintsa, D.F. Hurst, R. Jimenez, F.L. Moore, J.R. Spackman, and M.A. Zondlo, "Atmospheric observations of Arctic Ocean methane emissions up to 82° north", Nature Geoscience, vol. 5, pp. 318-321, 2012.
  6. S. Kirschke, P. Bousquet, P. Ciais, M. Saunois, J.G. Canadell, E.J. Dlugokencky, P. Bergamaschi, D. Bergmann, D.R. Blake, L. Bruhwiler, P. Cameron-Smith, S. Castaldi, F. Chevallier, L. Feng, A. Fraser, M. Heimann, E.L. Hodson, S. Houweling, B. Josse, P.J. Fraser, P.B. Krummel, J. Lamarque, R.L. Langenfelds, C. Le Quéré, V. Naik, S. O'Doherty, P.I. Palmer, I. Pison, D. Plummer, B. Poulter, R.G. Prinn, M. Rigby, B. Ringeval, M. Santini, M. Schmidt, D.T. Shindell, I.J. Simpson, R. Spahni, L.P. Steele, S.A. Strode, K. Sudo, S. Szopa, G.R. van der Werf, A. Voulgarakis, M. van Weele, R.F. Weiss, J.E. Williams, and G. Zeng, "Three decades of global methane sources and sinks", Nature Geoscience, vol. 6, pp. 813-823, 2013.

129 Responses to “Arctic and American Methane in Context”

  1. 51
    wili says:

    Thanks for that, Kevin. So when you posted “20 years ago believed to be negligible” above, you meant “believed to be, but probably not”??

    “*IF* it were the case that arctic methane had doubled and then doubled again in such a short period of time and continued to do so, we’d all be up the proverbial creek without a paddle.”

    This is precisely why those of us who (in the words of the recently departed educator, Dr. Bartlett) ‘understand the exponential function’ are so concerned. Again, the operative quote is here:

    “Since 1994, Igor Semiletov of the Far-Eastern branch of the Russian Academy of Sciences “has led about 10 expeditions in the Laptev Sea but during the 1990s he did not detect any elevated levels of methane.”

    Is there good reason to believe that Semiletov is being misquoted or misunderstood here, or is the area of the Laptev he observed to small to be significant?

    Just trying to understand how we might come to the conclusion that these are long term emissions (which I hope we can determine) rather than rapidly increasing ones (which I hope we don’t conclude, but I do want to know one way or the other).

  2. 52
    Kevin O'Neill says:

    Gavin #50, I love how internet conversations evolve. Do you even remember the genesis of this thread? HR made a comment in #22 “But if they’ve (Shakhova & Semiletov) agreed nobody has been able to show hydrates above the stability zone, no shallow, metastable hypothetical hydrates found — that should revise the expected methane bomb down to 1/50th — 2 percent — of the claimed size.”

    I replied in #33 that the literature supports the existence of hydrates outside the P-T calculated HSZ. That most of this has been written by Russian researchers.

    You then chimed in refusing to admit their existence. And we go round in circles.

    Now you attribute to me: “Your absolute confidence that this is the source is not apparently shared by the researchers you’re championing”

    Where have I made this statement or anything close? I’ve merely pointed out that numerous researchers, most of them Russian, have demonstrated the existence of meta-stable hydrates outside the conventional HSZ. That they’ve been found in other similar geologic areas and thus it’s likely they will be found in the ESAS.

    When you asked for the methane sources I said permafrost and deep sediment venting. Never have I tried to quantify the occurrence of meta-stable hydrates or inferred that they are the predominant source of arctic ocean methane.

    The allusion to peer-review means you’re probably aware most of the papers that have been published included far more examples than actually ended up in the final product. E.g., one early manuscript I found refers to meta-stable hydrates at 20m depth; the final paper was raised to 60m. Another paper had all references to marine meta-stable hydrates removed – even though the original work relied mostly on marine hydrates. Reading between the lines I just assumed they ran into reviewers with attitudes like yours – reviewers that just refused to believe these meta-stable hydrates exist or could exist at such shallow depths.

    [Response: I think it far more likely that peer reviewers actually asked that the conclusions of papers actually follow from what was presented and observed rather than imagined. A claim that “X exists somewhere, Y might be associated with X in some circumstances (though Y could arise from many different factors), we have observed Y, therefore X” is just not that convincing. And going from that to stating that it is likely that Y is going to increase by two orders of magnitude any day now is simply unsupportable. I am happy to read more about this, and I have never claimed that there aren’t important methane and carbon feedbacks in the Arctic, but the scenarios that people are discussing (and calculating economic damages from!) are entirely fanciful. People have taken cores in the ESAS (even Shakhova and colleagues) and yet there are no direct observations of these hydrates, let alone 50 GtC of them. – gavin]

  3. 53
    Sean says:

    @44 Dear Hank, would you mind qualifying exactly how you arrive at the phrase “you have been misinformed; found that misinformation widely available, from unreliable sources.”

    NASA issued a press release (that should be read in full by clicking the link below) on the CARVE mission which is using a very low flying, specially instrumented, airplane to study the details of Arctic CO2 and methane release. Cutting to the chase – the preliminary results – NASA’s PR report is disturbing.

    and more .. did you note WUWT as the #1 search result then mentally shut down or something? About 5,290,000 results … clearly you didn’t dig very deep nor view to the bottom of the page here. Nor did you do more targeted exact key word searches. Please explain your position, as it is most unclear what the basis for your claim actually is bar a personal “belief”. Thx Sean

  4. 54
    AbruptSLR says:

    The following quote comes from the article (by David):
    “Sea level dropped during the last glacial maximum, but there was no ice sheet in Siberia, so the surface was exposed to the really cold atmosphere, and the ground froze to a depth of ~1.5 km. When sea level rose, the permafrost layer came under attack by the relatively warm ocean water. The submerged permafrost has been melting for millennia, but warming of the waters on the continental shelf could accelerate the melting.”
    However, as the ESAS was only inundated by the sea about 8,000 years ago it would be highly unlikely to find that about 1.5 km thick subsea permafrost layer would have decomposed sufficiently by the Holocene Optimum to have allow significant amount of methane to leak through it. Nevertheless, by modern times according to Shakhova et al 2010, the area of this ESAS submerged permafrost affected by active fault zones and by open taliks – zones of permafrost that have melted – were 1-2% and 5-10% of the total area respectively. As gases methane would clearly accumulated under an impermeable permafrost cap for the past several thousand years, and as prior to 2010 the ESAS had 5-10% taliks, it is not surprising to say that these observed taliks would have released gases methane from beneath the subsea permafrost in modern times, and that more taliks are likely to continue to be forming. Furthermore, seismic activity has been proven to locally destabilize subsea methane hydrates at many sites around the world. Thus only does not need to postulate a massive destabilization of ESAS methane hydrates, nor to postulate a 50 Gt methane gas reserve, in order to see that continued degradation of the subsea permafrost and continued seismic activity, are sufficient to increase ESAS methane emissions to at least 0.4 Gt/yr (from the current 0.02Gt/yr) within the next few decades; which according to my post #20 may be sufficient to quadruple the current methane burden in the atmosphere by 2060.

  5. 55
    Michiel van Weele says:

    To contribute on the issue of satellite observations of methane such as from IASI. Yes, in Europe there is already about 10 years of experience in exploiting space observations of methane in the troposphere. This was pioneered by SCIAMACHY instrument on board of ENVISAT. Our paper in Science in 2005 showed the potential (Frankenberg et al.). These SCIAMACHY observations were backscattered sunlight observations and have good sensitivity to the planetary boundary layer. IASI is the current operational IR sensor on Metop. The methane retrievals are improving over time, and will likely get assimilated in near-real time at ECMWF in the MACC chemical assimilation system to provide in near-real time 3D global fields (and short-term forecasts) of methane. Current inversions rely on GOSAT observations, with eg involvement of JPL. Inversions combining satellite observations and surface data show we know quite the knowns and (regional) unknowns of methane sources. The inversions leave very little space for significant Arctic emissions or emission variations at present day. Please google on SCIAMACHY, GOSAT, IASI, and check the large literature available in eg JGR Atmospheres, ACP, etc. The Netherlands will contribute from 2015 onwards with likely best-ever spaceborne observations of methane with the TROPOMI instrument, part of the European Sentinel series (Sentinel-5p). This mission will allow mapping methane emissions per region and studying the interannual variability of methane emissions from eg tropical wetlands which is hard to monitor from the ground. No mysteries, no doom scenarios, just global-scale monitoring and explaining what you see, that is what we need to do as scientists.

  6. 56
    Dennis Denuto says:

    re relict hydrates; Gavin’s comments on this make sense… the issue is not whether such things exist – they likely do — the issue is the 50 GT number. If there was even 0.5 GT I’m thinking we would have much more evidence of such things than we now have. I will also note that even in Yakushevs most advanced studies these hydrates seem very rare…0.5 to 3% saturations? ESAS is possibly telling us something about methane in natural systems, but whether that something is even an uniquely Arctic story or more generic not is unclear. But I think it is pretty clear that is not a hydrate story.

    [Response: I would personally bet that metastable hydrates likely do not exist. It would be like an unmelting ice cube thousands of years old. David]

  7. 57
    wili says:

    There has been much discussion about previous warm periods, and about why those earlier relatively warm periods did not thaw this sub-sea material. Various arguments against this approach, largely ignored, have been posed.

    But, setting aside hydrates for now, I would like to pose a question from a different side of climate pre-history.

    It is my understanding that the previous ice ages have ended in the past by a forcing from changes in tilt of the earth (i.e. Milankovitch cycles). But that forcing would not have been sufficient in itself. There had to have been feedbacks that moved the global climate much further in the direction of warming than it would have gone just from the Milankovitch cycles. Am I right in this basic understanding?

    Further, the feedback must have included carbon, since the famous graphs show so clearly how closely the initial warming is followed by rises in CO2 (some of which, at least, could have come from CH4). Am I roughly right here, too?

    My question is: Since these earlier relatively slight forcings prompted such considerable carbon feedbacks that drove warming much further than it would have gone otherwise, should we not expect some sort of carbon feedback to kick in from our considerable ‘artificial’ forcing/warming?

    If so, and if it does not come from the ocean, where are we most likely to see this carbon mostly coming from? Permafrost? Other soils? permanently burned forests? All of the above?

    (I still find it a bit bewildering that, if we know well that carbon feedbacks were so crucial to every post glacial warming, this essential element has been left out of most models till recently.)

    [Response: Two reasons, no three. 1, The carbon cycle changes in the past were slow, order 1,000 years. 2, We don’t understand how they worked, so it’s impossible to do more than conject about whether and how they will operate in the future. 3. The carbon cycle today is actually acting as a negative feedback, absorbing our fossil fuel CO2. The differences are that we’re forcing it with CO2 rather than temperature (orbital forcing) and the timescale. Models aren’t there yet that can follow this curvey story. David]

  8. 58
    Steve Fish says:

    Re- Comment by wili — 3 Dec 2013 @ 9:08 PM

    “If so, and if it does not come from the ocean….”
    As the ocean cools, much more CO2 will dissolve in it and when the ocean warms again the CO2 is released. The carbon comes from the ocean and warming is further enhanced by increasing water vapor.


  9. 59
    wili says:

    Thanks, Steve. I had assumed that the CO2 that amplified the M cycles came from a variety of sources: terrestrial, aqueous and seabed… What you say makes sense. Do you happen to have a source where I can look further into it?

  10. 60
    Kevin O'Neill says:

    #52 Gavin, “People have taken cores in the ESAS (even Shakhova and colleagues) and yet there are no direct observations of these hydrates, let alone 50 GtC of them.”

    Gavin, why do you continue to play word games? As I pointed out above, they have been observed in marine sediments in the Laptev Sea bordering the ESAS. They’re part of the same continental shelf. Your position on this is silly.

    Furthermore, I believe Yakushev has estimated their coverage to be 0.5% to 3% of the ESAS (sorry, no reference at hand – I could be making this up :)). How many sites would you have to drill before the results would be significant enough to reject the hypothesis? Do you know how many ‘failed’ cores have actually been retrieved? It’s my understanding that it takes specialized equipment to ensure that the hydrate doesn’t immediately destruct when the sediment core is raised; i.e., no one has much data. This should give *more* weight to the fact metastable hydrates were found without even specifically looking for them.

    [Response: The ‘no one has much data’ should make you far more sceptical about extraordinary claims than you appear to be. But despite the difficulty, other people have looked, and they have not found. – gavin]

    Note, at the observed emission rate of 17 Tg/yr, and using the IPCC GWP of 34 for methane, we’re already at 50 GtC over 90 years. Though the source is, admittedly, up in the air (sic).

    [Response: This is a nonsense calculation. A new source of 17 Tg/yr continuously adds approximately 60 ppbv to CH4 concentrations. A radiative forcing of approximately 0.02 W/m2 (directly), or 0.04 W/m2 including various indirect effects. And since this hasn’t been shown to be a new source, impacts are even less. – gavin]

  11. 61
    Kevin O'Neill says:

    #51 wili – “Is there good reason to believe that Semiletov is being misquoted or misunderstood here, or is the area of the Laptev he observed to small to be significant?”

    I don’t believe he’s misquoted, but neither can any extrapolations be made from it. I don’t think anyone knows the answer to: How fast, if at all, are arctic methane emissions growing?. The levels are, at present, too small to have much impact on global levels. But if they’re growing (as a GW feedback) at a substantially high rate, say 7%/yr, then we’d be looking at triple David Archer’s worst case emission scenario to year 2100.

    Not only don’t I have a clue as to what the actual rate is, I don’t even have anything to put forward as a reasonable guess. But if the yearly emissions estimate doubles again in the next 5 years we’ll be fast approaching 12 noon in Bartlett’s terminology.

    [Response: If you don’t know the rate of growth (which is fine since there is no evidence for anything substantial), I wouldn’t discuss the possibility of emissions doubling ‘again’. – gavin]

  12. 62
    Tony Weddle says:


    At what point will CO2 be released from the oceans? The oceans are warming now but they are still a CO2 sink (hence acidification), even if the rate is slowing.

    [Response: Not any time soon. The rate at which CO2 is taken up can of course vary, but I don’t think any projections (at least until 2100) show net outgassing. (Trying to find a relevant reference…). – gavin]

  13. 63
    Steve Fish says:

    Response to Comment by wili — 4 Dec 2013 @ 12:30 AM

    This article by Joe Barton at Skeptical science is a good explanation and provides references:


  14. 64
    Steve Fish says:

    Response to Comment by Tony Weddle — 4 Dec 2013 @ 4:30 AM

    As usual, it’s complicated. Here is a good referenced article on The Ocean’s Carbon Balance from the NASA Earth Observatory:


  15. 65
    wili says:

    Thanks again, Steve.

    Since one crucial question here seems to involve the rate of increase (if any) of these methane emissions–here’s a piece that may throw some light on the question:

    ” Release of Methane in Deep Ocean Ice

    Trapped deep in the ocean floor are huge quantities of methane hydrates frozen in ice structures called clathrates. The total amount of marine methane hydrates could be as much as 100 to 2000 times the amount of methane currently found in the atmosphere. If the ocean floor were to warm sufficiently, causing melting or increased underwater landslides, some of this gas could be released and bubble up to the atmosphere, leading to more global warming. A recent survey of the ocean waters above the East Siberian Arctic Shelf may have located the first signs of such methane release.

    Igor Semiletov and his colleagues measured methane bubbling up at a rate 10 times faster than just a decade ago, contributing to spikes of methane in the atmosphere up to 4 times greater than the global average concentration.”

    This came out in 2009. So Semiletov was, apparently, doing research in ESAS in 1999 (if not earlier) and the rate seems to be increasing by a factor of ten per decade. So if this rate continued we would have 200 Tg in a decade being emitted from the area per year, and 2000 Tg in two decades?

    But perhaps the person writing this story got something wrong?
    And is the implication of some of the mods that S&S are basically not to be trusted to present accurate findings?

  16. 66
    wili says:

    Further info on what was being collected when: From a 2003 abstract:

    “Hydro-chemical anomalies obtained over the shallow Siberian shelves demonstrate significant role of coastal erosion in the formation of the biogeochemical regime in the Arctic seas (Semiletov, 1999; Dudarev et al., 2001)”

    (Thanks to “Cid_Yama” at Maltusia blog for these links.)

  17. 67
    Hank Roberts says:

    > the hydrate doesn’t immediately destruct

    That depends on rate of change of both temperature and pressure.
    Observations were surprising and unexpected when tested some years ago:

    I’m sure you can find more recent work pubished, that’s quite a while ago.

  18. 68
    Hank Roberts says:

    Thanks to Michiel van Weele 3 Dec 2013 at 5:14 PM above for the pointer to the Report he coauthored; that’s
    Science 13 May 2005:
    Vol. 308 no. 5724 pp. 1010-1014
    DOI: 10.1126/science.1106644
    Assessing Methane Emissions from Global Space-Borne Observations

    C. Frankenberg, J. F. Meirink, M. van Weele, U. Platt, T. Wagner

    and for the thoughtful post. Hearing from working scientists here is enormously helpful — both what you’ve done in the past and what you’re working on now, and what you think.

    I hope you’ll keep giving us pointers to real information as you did above.

    Please google on SCIAMACHY, GOSAT, IASI, and check the large literature available in eg JGR Atmospheres, ACP, etc. The Netherlands will contribute from 2015 onwards with likely best-ever spaceborne observations of methane with the TROPOMI instrument, part of the European Sentinel series (Sentinel-5p). This mission will allow mapping methane emissions per region and studying the interannual variability of methane emissions from eg tropical wetlands which is hard to monitor from the ground. No mysteries, no doom scenarios, just global-scale monitoring and explaining what you see, that is what we need to do as scientists.

  19. 69
    Hank Roberts says:

    Wili, the NWF link you posted above repeats the same claim that appears many other places, it’s not news, and it’s not new. That says, without a cite:

    A recent survey of the ocean waters above the East Siberian Arctic Shelf may have located the first signs of such methane release. Igor Semiletov and his colleagues measured methane bubbling up at a rate 10 times faster than just a decade ago …

    It’s the same story posted, reposted, and reposted over and over and over.

    Seriously, no matter how many times a claim is copypasted to a new Google link, no matter how big the Google hit count goes up — it’s the same item.

    It’s been claimed once, unsupported — and reposted thousands of times, as whatsisname illustrated a while back with the same notion.

    Multiple copies generate more links and search hits that benefit the SEO “optimizers” — hit rates pay them money. People load their pages with multiple copies to get more clicks — but that’s nothing new.

  20. 70
    wili says:

    Thanks for your response to my inquiries at #57, David. There you write: ” 2, We don’t understand how [earlier carbon feedbacks] worked, so it’s impossible to do more than conject about whether and how they will operate in the future.”

    I find little here to take comfort in (not that it’s your job to comfort us).

    Given that every other time there was a temperature forcing, the system eventually responded with a re-enforcing carbon feedback, it would seem pretty likely that the same will happen eventually this time.

    [Response: I feel it’s as if we sit under a sword of Damocles, within a very viscous fluid in which it will take a long time for the sword to reach us if (when) the string breaks. David]

    I guess the whole debate here boils down to the definition of ‘eventually’: How soon and how abruptly might we switch from net negative carbon feedback to net positive?

    I join hank in thanking not only Michiel van Weele but all those struggling, often heroically, to research these important developments and to make that information broadly available.

  21. 71
    Hank Roberts says:

    ps for Wili, WWF has been

    … working to institute a system to ensure that the scientific community and the public can more easily distinguish between WWF’s peer-reviewed scientific reports and our general communications products….

  22. 72
    Hank Roberts says:

    disambiguation, to be clear: both the NWF and the WWF produce both peer-reviewed science and more general blogs and columns. I mention the WWF as an example of the problem any such group may have when their general blogs and columns make claims without cites — don’t assume everthing you read is good science. Their hearts are in the right place, but their cites may or may not be.

  23. 73
    wili says:

    Ha! Thanks for the WWF link, hank. My bro used to be their main man in China so I used to stay on top of what they were doing more (before he went on to run IATP; the over-achiever in the family–my job is to hold down the other end of that spectrum ‘-)).

    Good stuff, especially at the global level.

  24. 74
    Joseph O'Sullivan says:

    #65 Wili,

    If you go to the National Wildlife Federation page you cite and go to the pdf they link to, the NWF is citing a 2008 National Geographic news story about Semiletov’s AGU presentation. National Geographic interviews Semiletov for the article and the “spikes of methane in the atmosphere up to 4 times greater than the global average concentration” comes directly from a quote from Semiletov.

    The NWF in the following paragraph states that the chances of mass marine methane hydrates releases are remote, but if this does happen the result’s can be very serious (and cite a paper published in Nature) so it cannot be ignored.

    It is important to remember that the environmental groups are political advocacy groups. How accurate are their claims depends on how they use the science. This varies from group to group, but the major U.S. groups are sophisticated and have working scientists on their staffs. Although they tend to play up the worst case scenarios, they usually don’t make baseless claims.

    Over at the environmentalist news site Grist, I have been arguing that environmentalists should be careful about making claims that cannot be based on scientific facts. Recently the stories about the papers that are the subject of David’s post have come up, and I think the Grist author’s are making claims that the studies really can’t support.

  25. 75
    wili says:

    Thanks for those perspective, jo and hank.

    It was mostly Russians researching these areas before this century and they mostly published in Russian and in Russian journals. Here are some relevant papers:

    Papers dealing specifically with the ESAS prior to 2003.

    Semiletov I.P., N.Ya. Pivovarov, I.I. Pipko, A.Yu. Gukov, T.I. Volkova, J.P. Sharp, Yu.S.
    Shcherbakov, and K.P. Fedorov, 1996, Dynamics of dissolved CH4 and CO2 in the Lena
    River Delta and Laptev Sea. Transactions (Doklady) of the Russian Academy of Sciences, 350(3), 401-404 (translated into English).

    Semiletov, I.P., 1999, On aquatic sources and sinks of CO2 and CH4 in the Polar Regions, J.
    Atmos. Sci., 56, 286-306.

    Semiletov, I.P., 1999, Destruction of the coastal permafrost ground as an important factor in
    biogeochemistry of the Arctic Shelf waters, Trans. (Doklady) Russian Acad. Sci., 368, 679-682 (translated into English).

    Naidu, A.S., L.W. Cooper, B.P. Finney, R.W. Macdonald, C. Alexander, and I.P. Semiletov,
    2000, Organic carbon isotope ratios(δ13C ) of Arctic Amerasian continental shelf sediments,
    Int. J. Earth Sci. (Special issue: Arctic Paleo-River Discharge), 89, 522-532.

    And a further quote from the NaGeo article:

    “‘Our early observations in 1994 to 1999 didn’t reveal a widespread enhanced dissolved methane concentration’ along the Siberian coast, Semiletov said.”

    On a lighter note, here is a beautiful and somewhat creepy video of a ‘brine-icle’ transporting very cold brine down from below the sea ice to the ocean floor and freezing everything in its path. Just shows that there are all sorts of weird, unexpected ways that temperature, salinity … can be communicated from one level to the other in the ever-surprising Arctic.

  26. 76
    wili says:

    Here’s the link to that video:

  27. 77
    Tony Weddle says:

    So, we have quotes from a scientist doing field work along the Siberian coast, showing that methane emissions from the ESAS were negligible, more than 10 years ago but are now far, far greater. We have other scientists who appear to show disbelief in such statements.

    Who should a layperson give more weight to? Why do we have such apparent disparate views? Whether it is shallow hydrates or free methane (perhaps from hyudrates) previously under an impermeable permafrost cap, something does appear to be happening up there. Some scientists think there is nothing much to worry about yet and others think there is. And there seems to be some animosity between those who consider themselves experts on this (not just S&S) and others who consider themselves experts on this. But who are the experts and, to repeat, who should a layperson give more weight to?

    I’m trying to understand what is going on the in Arctic but it seems to be an impossible task, though some people (on both sides) seem perfectly convinced of their alternate views.

    Does anyone have a way to get to the (likely) truth of the matter?

  28. 78
    Anonymous Coward says:

    Tony (#77),
    The way out of your conundrum may simply be not to get carried away with qualitative rhetoric (“far, far greater” or “worry”) and leaps of logic and to focus on the specific claims beign made.
    As far as I can see, there’s only one “side” who has spoken competently in quantitative terms about the global impact of this stuff.
    If there are bubbles of methane here and there boosting the local CH4 concentration spectacularly but which on the global level amount to less than 3% of the effect of CO2 emissions from fossil fuels, what does it matter really?

    A layman may also watch the CH4 readings from the monitoring stations whose data is released to the public in a timely manner.
    If there are new sources of methanes which aren’t “negligible”, where is the stuff hiding?

  29. 79
    Hank Roberts says:

    > Does anyone have a way to get
    > to the (likely) truth of the matter?

    Tony, did you read what Michiel van Weele wrote just above. at 3 Dec 2013 at 5:14 PM?

    He’s been actively involved in actually doing the work to answer the questions.

    Getting finer resolution data on sources of pollution will identify point-source problems, where throttling is feasible.

  30. 80

    Tony, I don’t see anyone “disbelieving” statements about increased methane release in the ESAS.

    I do see folks saying that there’s no evidence of a short-term ‘bomb’, so far, since the known hydrate inventory–the massive reservoir–is not ‘metastable’ and thus will thaw only gradually.

  31. 81
    AbruptSLR says:

    Regarding the various mechanisms that Semiletov and Shakhova view as influencing carbon emissions from the ESAS, I recommend reviewing the following open access article:

    Igor P Semiletov, Natalia E Shakhova, Valentin I Sergienko, Irina I Pipko and Oleg V Dudarev; “On carbon transport and fate in the East Siberian Arctic land–shelf–atmosphere system”, IOP PUBLISHING ENVIRONMENTAL RESEARCH LETTERS; Environ. Res. Lett. 7 (2012) 015201 (13pp) doi:10.1088/1748-9326/7/1/015201

  32. 82
    Hank Roberts says:

    Tony, I’ve tried to imagine the conditions in which the Russian warnings could be serious; near as I can tell they’d need something different now, some new mechanism for carrying heat down into the stability zone. Something that did not happen in the paleo record.

    For example, is the seabed there riddled with unplugged boreholes from oil and gas exploration? Enough to allow warm water to circulate down deep through gravel beds into the “stability zone” where hydrates are found.

    Or are there now somehow far more faults in the permafrost than existed in paleo times?

    That mechanism would be analogous to how an aquarium undergravel filter works — bubbles rising up one opening draw water down through other openings.

    That would warm material faster than it can warm by heat diffusing through intact sediment.

    I did my tinfoil-hat-best in to describe that hypothetical. There’s a link there to a picture of how that works in aquaria, search for “undergravel filter”

    But that’s pure speculation. That’s an attempt to guess what could possibly be behind the claims being made that it’s a problem now that didn’t happen the last time the area was as warm or warmer than now.

    What could be worse? Dump old nuclear reactors onto the seabed near open boreholes, say, or on top of open faults that would lead warm water down to the stability zone? Could have happened.

    Are there sensors in the area we aren’t told about? You’d expect so, since several nuclear navies have been active in the Arctic for decades. But we don’t know.

  33. 83
    wili says:

    AC at 78 wrote: “If there are bubbles of methane here and there boosting the local CH4 concentration spectacularly but which on the global level amount to less than 3% of the effect of CO2 emissions from fossil fuels, what does it matter really?” It matters if the levels are increasing at an exponential rate. That seems to be the main question before us.

    Hank: As usual, many good points. On the last bit, would point out that one scientist that I know has been working closely with the Royal Navy in the Arctic since the ’70s is Peter Wadhams, and he is far from sanguine about the rapidly changing conditions there and their likely consequences. (It is rather a pity that he threw his authority behind the AMEG folks, many of whom do…sloppy work sometimes and most of who have become rather rigidly ideological, in my view. But the very fact that he was drawn in that direction speak–to me–to the likely extremes situation he sees the situation being in from his advantaged, long-term perspective on the area.)

    “He has pioneered the use of AUVs (autonomous underwater vehicles) to measure under-ice topography and has worked with the Royal Navy since the 1970s in carrying out ice thickness measurement work from Navy submarines on Arctic deployments.”

    I have not taken the time yet to find out what other major researchers have worked with various navies in the area. Do you know of any?

  34. 84
    Hank Roberts says:

    Wili, I don’t know but I wouldn’t expect to know. We need politicians to order their Navy information released, as Al Gore ordered some of it released in 1998.

    But with a long history of dumping, and now with commercial competition and territorial claims heating up in the Arctic I suspect secrecy will not relax.

  35. 85
    Sean says:

    @81 re Received 5 August 2011 – Accepted for publication 6 December 2011 Published 4 January 2012
    Page 11 Summary Statements
    “To answer these questions we call for extended
    international cooperation in studying the ESAS. Such study
    will require multiple year-round exploration campaigns,
    including drilling of sub-sea permafrost to evaluate the
    sediment CH4 potential and comprehensive atmospheric
    measurements to assess the ESAS strength as a greenhouse gas source.
    “International effort should also be joined in order to quantitatively assess future changes in greenhouse gas emissions in response to ongoing climate change by establishing and developing regional numerical models with the aim of incorporating them into global climate models.”

    I have no idea as the the scientific validity nor qualitative rigour of the work done by the Russians. What I do know is that the pattern of human psychology is constant across the boundaries of individuals whose beliefs are either pro or con a particular hypothesis based on existing hard evidence. The beliefs and opinions vary, whilst the psychology of forming them and defending them are not. The modus operandi is in fact exactly the same.

    Denial is not a river in Egypt. Dismissiveness is dismissiveness always backed up by rhetoric and sophistry and usually not by hard evidence. An absence of evidence is NOT evidence of absence. Until such times as the appropriate basic research has been done and analysed properly. Rhetoric is not science, it is only ever about talking and listening.

    The Russians have repeatedly asked for help from the rest of the global scientific community on the subject of the ESAS. This doc is but one example of that.

    28 months later, since they wrote this quoted Paper/article, some elite and well resourced scientists cannot even bring themselves to send the authors an email or make a phone call to inquire what the authors evidence and opinions as of Dec 2013, or if there is some new papers coming out soon on this subject.

    Yet they do have all the time in the world to waste arguing about the absence of evidence on a discussion board with the general public and defending their beliefs not based on evidence. This reminds me of WUWT and Curry’s & Jo Nova’s blogs and the US Congress debates over Climate Science. Incredible maybe, but it seems to be true. Aaah but would I know about such matters? Carry on.

  36. 86
    Sean says:

    @83 RE: ” It matters if the levels are increasing at an exponential rate. ”

    Are Humans Smarter Than Yeast? (about exponential growth)

    The answer to the question is typically: NO.

  37. 87
    wili says:

    Unfortunately, I think you are likely right, hank. Thanks (yet again) for that link. I had not known that Gore tried to do (or if I did once, I have long since forgotten it—happening more and more these days :-/ ).

  38. 88
    Tony Weddle says:


    Yes, I read the comment you linked to but am no clearer about the likely situation up there. Wili points to Wadhams, Shakhova and Semiletov who would all regard the situation as somewhat worse than Archer and Schmidt do here, with the definite potential for abrupt releases. Wili has also pointed to information suggesting that we did have data (collected by Semiletov) in the 90s which showed no elevated methane emissions in the ESAS but now we have 17 TgC per year, estimated. Is that not a worry to Archer and others? If not, why not?

    Anonymous Coward,

    The worry is not so much that there is already an abprupt release (though methane concentrations are on the rise) but that there are pathways for such abrupt release. The problem may not be metastable hydrates but free methane beneath subsea permafrost.

  39. 89
    wili says:

    I would just like to point out one perhaps telling juxtaposition in the last line from the generally excellent and helpful post made by van Weedle at #55: “…no doom scenarios, just global-scale monitoring…”

    Contrasting these two this way makes it sound as if scientific collection of facts from “global-scale monitoring” can somehow never lead to “doom scenarios” and that, if they do, the monitoring or its interpretation must be suspect; not really a valid assumption afaics. But perhaps I’m misinterpreting the assumption behind this contrast somehow?

    (In any case of course, plenty of facts and interpretations from climate-related global monitoring of various sorts are indeed already pointing in very doomy directions, more and more so every week, it seems. At this point, a certain amount of “doom” is pretty much baked in. The operative question is how fast and how much. And, of course, at least some of what will determine those “how’s” will always remain partly in our individual and collective hands, depending on how soon we choose to stop making the problems worse, i.e., how soon we choose to stop burning ffs, and stop breeding and eating methane-producing animals…)

    (reCaptcha oracle implores: “act rkholid” …now if I only knew what ‘rkholid’ meant, I would know how to start to act ‘-))

  40. 90
    wili says:

    Has anyone else read the recent report from the National Research Council of the National Academies? It discusses this issue and concludes that sudden release of methane from ESAS is unlikely this century, but that the area needs to be studied more. It’s long, but well worth a perusal, at least, imho.

    (I hope my bringing up this important work helps people to see that I don’t see this as some kind of high school debating club, but as a forum to bring forward as much relevant research as possible to increase general understanding of the issues.)

    Of course, this report does not represent new research, afaics, just an assessment of older work. And, of course, such collective efforts tend to be conservative. I hope we can all agree with their conclusion that more research is needed in this (and in a number of other) crucial area(s).

  41. 91
    wili says:

    I just go to the section where they get into discussing Arctic seabed methane in more detail, and the conclusion of that section is actually: “In summary, the ocean methane hydrate pool has strong potential to amplify the human CO2 release from fossil fuel combustion over time scales of decades to centuries.”

  42. 92
    wili says:

    Here’s a link to a video of presentations given upon the release of this report two days ago:

  43. 93
    wili says:

    Thanks for your response at #70, David. “I feel it’s as if we sit under a sword of Damocles, within a very viscous fluid in which it will take a long time for the sword to reach us if (when) the string breaks.”

    Striking analogy! I guess what is up for debate is not so much whether there is a sword, but how big it is, how thin and frayed the string is (when/if it will break), and how viscous the fluid is. (I must admit that my old eyes first read ‘vicious’; perhaps equally fitting.)

    Anyway, thanks again for the response, and for all your important work.

  44. 94
    Kevin O'Neill says:

    #61 Gavin

    [kto]”Not only don’t I have a clue as to what the actual rate is, I don’t even have anything to put forward as a reasonable guess. But if the yearly emissions estimate doubles again in the next 5 years we’ll be fast approaching 12 noon in Bartlett’s terminology.”

    [Response: If you don’t know the rate of growth (which is fine since there is no evidence for anything substantial), I wouldn’t discuss the possibility of emissions doubling ‘again’. – gavin]

    Once again you respond to something I didn’t write. I didn’t say emissions doubling again, I said emissions *estimates.* I expect words to be twisted on denier sites. Not here. Or are you now going to claim that the emissions estimates haven’t doubled in just a few short years?

    [Response: Fair point, apologies. However the estimates of natural CH4 sources are all quite uncertain – with the main constraint being on the total emissions, not individual sources. Thus any reexamination of any particular source usually just rejiggles the ordering of terms, but doesn’t really change the overall picture. Even if ESAS estimates doubled again, it is still a small number. – gavin ]

  45. 95
    wili says:

    Good recent articles in the Guardian and at ClimateCentral on Arctic ice modeling and on Arctic ice loss effects on weather.

    (And what am I to make of reCaptcha’s exhortation: “titleMe she”?? Is it channeling the Ridar Haggar novel?)

  46. 96
    Dennis Denuto says:

    Here is what I don’t understand about this Arctic business. This shelf has been hit with a gigantic thermal pulse of 13C as relatively warm water replaced cold air. So why do we think that an extra degree or two of air temperature change above that water is going to be some key tipping point?

  47. 97
    Tony Weddle says:


    You implied that there was nothing in the paleo record showing a rapid release of methane but there was a paper in October suggesting a very rapid release which caused warming of 5C in 13 years (and rendered the ocean surface acidic). There is a report of the paper at Climate Progress.

    I couldn’t find the paper mentioned at RealClimate and wondered why that paper appears to have been overlooked?

    [Response: Wow, that’s a great paper. A game-changer. They have evidence that the carbon was released as you say very quickly, essentially instantaneously. I’m not a field geologist, but this looks to me like the kind of geologic section one would click one’s heels together to make a wish for, like I heard Steve Gould describing the Burgess Shale. Fantastic! Zachos measured individual foram shells from the deep sea, and found that for the planktonic ones, they were either heavy or light, never transitional. For benthic ones, there were transitional ones. Seemed to me that was also evidence for an abrupt carbon release, but Jim pointed out that dissolution might have created the signal he saw. This changes the playing field considerably for proposed sources.

    They also weigh in on the magnitude of the 13-C change and the amount of C released. They extrapolate the 13-C spike in the ocean against depth to estimate an atmospheric 13-C change, just after the carbon has been added to the atmosphere and before it invaded the ocean much at all, to get 20 o/oo. Then the magnitude of the carbon spike depends on its isotopic composition. This is a slightly different constraint than the previous calculation everyone’s done of the 13-C change in the deep ocean, representing the signal after it’s all mixed in (at least a few thousand years later). The results of the two seem to be similar on one end of the spectrum, in that biogenic methane (-60 o/oo) requires about 1000 Gt C. But the amount of carbon required to achieve an atmosphere of -20 o/oo with organic matter is prohibitively large. So they end up picking thermogenic methane of -40 o/oo as a feedstock. I guess I’m dubious on this conclusion; the extrapolation to an atmospheric 13-C seems like a sketchy way to eliminate the possibility of a larger, less isotopically labeled organic carbon source.

    Because there is still the constraint that the carbon has to lead to the warming. They state that addition of 3000 Gt C to an atmosphere of 2000 Gt C would lead to warming of 5 degrees C, but I don’t believe it unless the climate sensitivity is much higher than today. This is the issue raised by Pagani et al (Science 2006 10.1126/science.1136110). The warming has to be due to CO2, as evidenced by its duration. The atmospheric fraction of that instantaneously released CO2 would drop quickly as it invaded the oceans, while the thermal response of the Earth will be slowed by the thermal inertial of the oceans. So on the time scale for temperature equilibration of the Earth, you’d probably have less than a doubling of atmospheric CO2, not enough to get 5 degrees C if the climate sensitivity is as today about 3 degrees C.

    Truly a cautionary tale, and the geologic record is full of them. But I maintain that the best way to assess whether a methane blowout is likely in the near future is the world as it is at present. We are still at the stage of speculating on the causes of the PETM. David]

  48. 98
    Sekerob says:

    Talking the infamous clathrate gun?

    Minutea, it’s thought the Bermuda triangle had it’s cause in acute transition of clathrates… ships can’t float in ‘boiling’ water.

  49. 99

    #96–“So why do we think that an extra degree or two of air temperature change above that water is going to be some key tipping point?”

    Briefly, we don’t. The warming is not limited to the air column; the waters of the Arctic Ocean are warming, too. Dramatically, in some cases.

    Here’s one paper on that:

  50. 100
    wili says:

    Good points, KM.

    Sekerob, iirc, the “Bermuda Triangle” is completely mythical. Careful statistical analysis of the frequency of losses at sea show no increases of such accidents in that area over any others in the Atlantic. Of course, that does not negate the possibility of the specific kind of event you seem to be claiming has happened with sudden methane release.