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| A satellite picture reveals permafrost melting around Liverpool Bay in Canada’s northwest territories. NASA Goddard Space Flight Center |
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| Figure 1: Global distribution of methane hydrate deposits on the ocean floor. Naval Research Laboratory |
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| Figure 2a: Vulnerable carbon sinks. CSIRO Global Carbon Project |
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| Figure 2b: Global average abundances of carbon dioxide and methane 1978-2011 |
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| Figure 3: Change in average annual land surface temperature since 1750. Berkeley Temperatures |
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| Figure 4. Estimates of fossil fuel resources and equivalent atmospheric CO2 levels, including (1) emissions to date; (2) estimated reserves, and (3) recoverable resources (1 ppm CO2 ~ 2.12 GtC). Hansen, 2012, figure 1; http://www.columbia.edu/~jeh1/mailings/2012/20120127_CowardsPart1.pdf |
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| Figure 5: Growth in CO2 and CO2 equivalent (CO2+CH4) during the Pleistocene and the Holocene. IPCC AR4 |
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| [ click on image to enlarge ] |
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| Peter Wadhams Sc.D., Prof. of Ocean Physics and head of the Polar Ocean Physics group, Cambridge University. |
Peter Wadhams: The 25 July post by Jason Samenow on the global economic impacts of methane emissions in the East Siberian Sea portrays the findings of our research as misleading, a statement with which I strongly disagree. Our work is based on a prediction of the magnitude and timing of methane emissions from the thawing of Arctic offshore permafrost by a scientist who has done extensive field work on this part of the ocean bed and is a globally recognized expert. We calculated the financial implications of these emissions for the world economy over a century and also considered the effect of the emissions on increasing overall global warming, obtaining a 0.6C figure by 2040. We rightly consider these to be substantial figures, which deserve wide circulation among climate scientists, and Nature and its referees agreed with us.This is what Nathan Currier said in a comment at the Washington Post:
In our analysis we showed that the overall cost of a given volume of methane release is relatively insensitive to the rate of release or, within limits, its timing, BUT that the cost is roughly proportional to the overall volume of release. Thus, even if you worked with a different projection by a lesser qualified scientist than Shakhova, and revised down the figure and scale of the 60 trillion dollars accordingly, I suspect the cost will still be substantial – and that is one clear finding: The planetary cost of Arctic warming far outstrips any possible benefits to shipping or natural resource exploration.
In support of its skepticism about methane emissions the article quoted authors who wrote before the enormous retreat of summer Arctic sea ice and its oceanographic effects became so evident. The mechanism which is causing the observed mass of rising methane plumes in the East Siberian Sea is itself unprecedented and the scientists who dismissed the idea of extensive methane release in earlier research were simply not aware of the new mechanism that is causing it.
What is happening is that the summer sea ice now retreats so far, and for so long each summer, that there is a substantial ice-free season over the Siberian shelf, sufficient for solar irradiance to warm the surface water by a significant amount – up to 7C according to satellite data. That warming extends the 50 m or so to the seabed because we are dealing with only a polar surface water layer here (over the shelves the Arctic Ocean structure is one-layer rather than three layers) and the surface warming is mixed down by wave-induced mixing because the extensive open water permits large fetches. So long as some ice persisted on the shelf, the water mass was held to about 0C in summer because any further heat content in the water column was used for melting the ice underside. But once the ice disappears, as it has done, the temperature of the water can rise significantly, and the heat content reaching the seabed can melt the frozen sediments at a rate that was never before possible.
The 2008 US Climate Change Science Program report needs to be seen in this context. Equally, David Archer’s 2010 comment that “so far no one has seen or proposed a mechanism to make that (a catastrophic methane release) happen” was not informed by the Semiletov/Shakhova field experiments and the mechanism described above. Carolyn Rupple’s review of 2011 equally does not reflect awareness of this new mechanism.
Therefore I robustly defend our research and commentary, and hope that rather than dismiss the substantial risk such a methane release poses, the response might be to support more intensive research on this problem.
Nathan Currier: Earlier this year, a small piece of rock exploded over Russia, breaking some windows and causing minor injuries, yet shortly thereafter, a congressional panel was convened here in Washington, DC on the risks of significant asteroid impacts, and the panel, after being told they were about 1/20,000 for the year, was also told by the experts that billions will need to be spent to prevent a “possible catastrophe”. John Holdren, President Obama’s chief science advisor, commented, "The odds of a near-Earth object strike causing massive casualties and destruction of infrastructure are very small, but the potential consequences of such an event are so large it makes sense to takes the risk seriously." Holdren was right: in assessing a risk, it is a product of the probability and the magnitude that counts in the end.
Nothing we do alters the risk of asteroid impacts, but our activities are profoundly altering the risks of unleashing powerful arctic carbon feedbacks. Like night and day with warming, where we don’t tend to notice that nighttime temperatures are increasing more rapidly than daytime ones, the scientific community’s assessments of risks tend to focus on those things which, by being more continuous, can have the daylight of quantitative analysis shone upon them more easily. But there is no question that the risks in the arctic that are rising most rapidly are the “nighttime” ones of abrupt changes. That is because there is already a 100% chance of increases in chronic emissions. Somewhat like larger and larger rocks hitting the earth, the risks of larger and larger methane pulses are certainly progressively smaller, but the important point here is that if we were to say conjecturally that in 1970 the risks of a 50Gt release might have been like the “city-killer” asteroid at 1/20,000, these risks now might have decreased by an order of magnitude. It is still not likely to happen now, with, let us speculate, a 1/2,000 risk, but because of the magnitude, as Holdren says, you should take this very seriously. Far more seriously, I might add, than a meteor striking the earth. Meanwhile, the leaked draft of the IPCC AR5 suggests that all arctic carbon feedbacks will be largely ignored in the report, even those that are more or less certain.Also noteworthy is what Nathan Currier said in response to comments by Gavin Schmidt, quoted in the New York Times:
I would add that articles like this, characterizing the Nature commentary as “mischief” and “hype,” contribute to climate illiteracy in their own way, full of mischief without coming from a denialist perspective. There are too many errors here to elaborate them all. First, it makes a complete red herring of methane hydrate, quoting Ruppel on hydrate stability, etc. Let it be noted: 50Gt of methane is only about 2% of estimated Eastern Siberian Shelf (ESS) total carbon, and would only be 7% of the free gas reservoir that lies under the hydrate layer. There are many possible gas migration pathways for methane excursions, from pingo-like structures, fissures, the taliks appearing more and more throughout the permafrost layer, slope failure, sediment or mudslides around the Lena delta, an endogenous seismic event along the Gakkel ridge, etc. Thus, hydrate is really not even needed for a methane catastrophe scenario at the ESS. None of the quotes, moreover, about hydrate distinguish between the exceptional situation at the ESS of very shallow waters and the hydrates elsewhere around the world, which are indeed mostly quite secure.
Despite this, Hansen considers methane hydrate one of the three main coming tipping points in the climate system. The article quotes David Archer, a clear outlier on this issue, in that he doesn’t even believe the PETM warming (55 million years ago) was caused by methane hydrate release, which is the dominant paleoclimate theory, based on isotopic evidence. Meanwhile, it also quotes a paper claiming that there is no evidence for any major hydrate release at all over the last 100,000 years, clearly not something that Archer would agree with, as he himself has written an authoritative paper on the methane hydrate release of the Storrega landslide event (~8000 years ago).
At the group 1250 (1250now.org), we are focusing now on precisely the opposite, the subtler changes in surface-produced methane that are likely with further loss of sea ice, but it is shocking to see a response like this one to an issue of obvious importance.
To close, no one doubts that a 50Gt release of methane is “unlikely” right now if you consider 1/2,000, let’s say, unlikely. But as the thermal signal of anthropogenic warming propagates into the sediment below such shallow waters as at the ESS, and given that the ocean currents are not the same now as they have been during the paleoclimatic past, such that paleoclimate cannot ultimately be used to constrain and quantify the actual risk, it is clear that the risks, unlike those of asteroids, are growing.
But that was clearly NOT the point of the Nature commentary. The point of the commentary was to note that the impact would be very, very big. So, to go back to Holdren, it should be taken very seriously.
Gavin Schmidt: Threshold releases even 1/10 as large as postulated would be clear in ice cores. There is nothing there. In more recent past, there have been a number of times when Arctic (not necessarily globe) has been significantly warmer than today. Most recently, Early Holocene, which had significantly less summer sea ice than even 2012. Earlier, Eemian 125kyrs ago was significantly warmer.
Nathan Currier: I find Gavin Schmidt’s points here very thin. Let’s review them:Let's also add a quote from an earlier post:
First, clearly no one is suggesting that during the 800,000 year period covered by ice cores there has been any such release. Further, David Archer, quoted in Revkin’s piece and a leading authority on such issues, has specifically discussed the possibility in a peer-reviewed paper (Archer, 2007) of fern diffusion allowing a Gt-scale release to escape detection in ice cores.
The problem with this argument, made repeatedly when this same issue erupted over a year ago, is that it is looking weaker than it did just a year ago: for example, we are learning that certain key ocean currents were significantly different during the Eemian than they are today – see http://phys.org/news/2012-06-climate-cold-arctic-eemian.html. And what counts in this argument is what the sea bottom conditions are, of course, not just the surface conditions. Schmidt is right that at times it was much warmer than today in the arctic, possibly 8C warmer, as we have seen from the Lake E work, but he forgets himself, and points to the early Holocene, although the area in question was a frozen piece of land at that time, not an underwater shelf, so that is purely irrelevant, as it took almost 4,000 years before the area in question became inundated.
But risks are growing significantly in the arctic by the year, and a 5Gt release, which would double the atmospheric burden, would result from less than 1% - about .7% - of estimated ESAS free gas below the hydrate layer being released, without any hydrate needing to be involved, which some kind of endogenous seismic event could conceivably set off, perhaps a sediment pile mud slide around the Lena mouth, for example. The point of the paper, lost in all of this, was just to say, this would cost us about $6 trillion.
The worst moment of Schmidt’s points, one which really merits censure, is to refer to all the research being done in the area (he clearly means Shakhova and Semiletov here) as “one off surveys.” Note that he isn’t even asking for better research to be done there, either. I personally find that quite unfortunate, even a bit embarrassing for someone who has built up a sterling reputation.
He (Schmidt) is certainly right that there is no recent example of CH4 being higher than the pre-industrial baseline, and that includes the “super-interglacials” from Lake E bores, but it is incredibly unwise to jump to the claim from that that we are not near dramatic releases without offering any evidence at all.
It is far better to go by the best peer-reviewed research about contemporary conditions on the ground than to speculate about the few generalities we can draw from the sketch of climates past we have put together for the last few million years, as valuable as that sketch is. There was at no time during that period anything like the 400ppm of CO2 in the atmosphere now, nor the many other GHGs levels we have boosted, nor the things that have no natural analogue like the CFCs, nor is there any analogue for the rate of change we have experienced, and so the sea level’s relationship to the atmospheric conditions has no analogue either, and we are also learning at the same time just how sensitive and variable key arctic ocean currents might be in this region.
All that said, Schmidt acknowledges that “potential for Arctic CH4 to have threshold behavior is real,” and I should also acknowledge that I agree that the 50Gt scenario is not likely at this time.
Sam Carana: Analysis of sediment cores collected in 2009 from under ice-covered Lake El'gygytgyn in the northeast Russian Arctic suggest that, last time the level of carbon dioxide in the atmosphere was about as high as it is today (roughly 3.5 to 2 million years ago), regional precipitation was three times higher and summer temperatures were about 15 to 16°C (59 to 61°F), or about 8°C (14.4°F) warmer than today.Also note the comments by Veli Albert Kallio, in an earlier post:
As temperatures rose back in history, it is likely that a lot of methane will have vented from hydrates in the Arctic, yet without causing runaway warming. Why not? The rise in temperature then is likely to have taken place slowly over many years. While on occasion this may have caused large abrupt releases of methane, the additional methane from such releases could each time be broken down within decades, also because global methane levels in the atmosphere were much lower than today.
In conclusion, the situation today is much more threatening, particularly in the East Siberian Arctic Shelf (ESAS), as further described in other posts at the methane hydrates blog.
Albert Kallio: The problem with ice cores is that if there is too sudden methane surge, then the climate warms very rapidly. This then results the glacier surfaces melting away and the ice core begins to loose regressively surface data if there is too much methane in the air.Let's conclude the debate on the following note:
Because of this, there has been previous occurrences of high methane, and these were instrumental to bring the ice ages ice sheets to end (Euan Nisbet's Royal Society paper). The key to this is to look at some key anomalies and devise the right experiments to test the hypothesis for methane eruptions as the period to ice ages.
Thus, the current methane melting and 1800 ppm rise is nothing new except that there are no huge Pleistocene glaciers to cool the Arctic Ocean if methane goes to overdrive this time. In fact methane may have been many times higher than that but all surface ice kept melting away and staying regressive until cold water and ice from destabilised ice sheets stopped the supply of methane (it decays fast if supply is cut and temperatures fall back rapidly when seas rose).
The Laurentide Ice Sheet alone was equivalent of 25 Greenland Ice Sheets and the Weischelian and other sheets on top of that. So, the glaciers do not act the same way as fireman to extinguish methane. Runaway global warming is now possibility if the Arctic loses its methane holding capability due to warming.
Sam Carana: Uncertainty does NOT constitute a valid argument to dismiss warnings about large abrupt methane releases in the Arctic. Instead, uncertainty calls for further research and for comprehensive and effective action, especially since so much is at stake and the dangers are getting larger each time the necessary action is delayed.