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An Arctic methane worst-case scenario

Filed under: — david @ 7 January 2012

Let’s suppose that the Arctic started to degas methane 100 times faster than it is today. I just made that number up trying to come up with a blow-the-doors-off surprise, something like the ozone hole. We ran the numbers to get an idea of how the climate impact of an Arctic Methane Nasty Surprise would stack up to that from Business-as-Usual rising CO2

Walter et al (2007) says that Arctic lakes are 10% of natural global emissions, or about 5% of total emissions. I believe that was considered to be remarkably high at the time but let’s take it as a given, and representing the Arctic as a whole. If the number of lakes or their bubbling intensity suddenly increased by a factor of 100, and it persisted this way for 100 years, it would come to about 200 Gton of carbon emission, which is on the same scale as our entire fossil fuel emission so far (300 Gton C), or roughly the amount of traditional reserves of natural gas (although I’m not sure where estimates are since fracking) or petroleum. It would be a whopper of a surprise.

Scaling Walter’s Arctic lake emission rates up by a factor of 100 would increase the overall emission rate, natural and anthropogenic, by about a factor of 5 from where it is today. The weak leverage is because the high latitudes are a small source today relative to tropical wetlands and anthropogenic sources, so they have to grow a lot before they make much difference to the sum of all sources.

The steady-state methane concentration in the air scales nearly linearly with the emission rate. Actually, the concentration goes up somewhat faster than a constant times the emission rate, because the lifetime in the atmosphere gets longer (IPCC TAR). Let’s err on the side of flamboyance (great word in this context) and say the concentration of methane in the air goes up by a factor of 10 for the duration of the extra methane emission (meaning that the lifetime doubles).

Using the modtran model on line I get a radiative forcing from 10 * atmospheric methane of 3.4 Watts/m2 (the difference in the instantaneous IR flux out, labeled Iout, between cases with and without 10x methane). Using the TAR estimates of radiative forcing gives 2.7 Watts/m2.

But methane is a reactive gas and its presence leads to other greenhouse forcings, like the water vapor it decomposes into. Hansen estimates the “efficacy” of methane radiative forcing to be 1.4 (Hansen et al, 2005, Shindell et al, 2009), so that puts us to 4 or even 5 Watts/m2.

This is about twice the radiative forcing today from all anthropogenic greenhouse gases today, or (again according to Modtran) it would translate to an equivalent CO2 at today’s methane concentration of about 750 ppm. That seems significant, for sure.

Or, trying to “correct” for the different lifetimes of the gases using Global Warming Potentials, over a 100-year time horizon (which still way under-represents the lifetime of the CO2), you get that the methane would be equivalent to increasing CO2 to about 500 ppm, lower than 750 because the CO2 forcing lasts longer than the methane, which the GWP calculation tries in its own myopic way to account for.

But the methane worst case does not suddenly spell the extinction of human life on Earth. It does not lead to a runaway greenhouse. The worst-case methane scenario stands comparable to what CO2 can do. What CO2 will do, under business-as-usual, not in a wild blow-the-doors-off unpleasant surprise, but just in the absence of any pleasant surprises (like emission controls). At worst comparable to CO2 except that CO2 lasts essentially forever.


  1. K.M. Walter, L.C. Smith, and F. Stuart Chapin, "Methane bubbling from northern lakes: present and future contributions to the global methane budget", Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, vol. 365, pp. 1657-1676, 2007.
  2. J. Hansen, "Efficacy of climate forcings", Journal of Geophysical Research, vol. 110, 2005.
  3. D.T. Shindell, G. Faluvegi, D.M. Koch, G.A. Schmidt, N. Unger, and S.E. Bauer, "Improved Attribution of Climate Forcing to Emissions", Science, vol. 326, pp. 716-718, 2009.

159 Responses to “An Arctic methane worst-case scenario”

  1. 1
    R. Gates says:

    Very interesting. Really puts a perspective on it. I am curious as to what additional slower “earth-system” feedbacks might be indicated by the release of the methane…i.e. what kind of biological changes might occur to arctic regions by the melting of permafrost and release of methane that will add a longer-term feedback response that needs to accounted for before any sort of new equalibrium would be reached.

  2. 2
    Mike Roddy says:

    Thanks for addressing this, David. The point that tends to get overlooked here is that substantive but incremental forcing increases can lead to nasty but as yet unknown surprises. We have seen some already, in the rapid disappearance of Arctic summer ice, the accelerating glacier melts in Greenland, and heat waves and forest fires in North America and Asia. These events were not predicted to occur in the context of our current 1C warming. IPCC and mainstream climate science have been shown by events to be far too cautious.

    Everyone here should read Nassim Taleb’s Fooled By Randomness, a brilliant book showing that humans do not prepare well for unusual future hazards. There are many trite descriptions of ways to correct this- “err on the side of caution”, etc- but these strategies are nowhere near manifested in current energy policy. According to Taleb, small probability disasters (his example was trading “blowups”) are near inevitable in the long term.
    In the case of global warming, it is clear that GHG’s could have terrifying consequences.

    Our emissions policies should be driven by the worst case, since the worst case is truly catastrophic to life on earth. Your elaboration of our future confused me- if worst case methane bursts are roughly equivalent to CO2 emissions, and therefore somewhat manageable, this represents an outlier opinion. Storms of my Grandchildren lays this out in detail.

  3. 3
    Geoff Beacon says:

    But the methane worst case does not suddenly spell the extinction of human life on Earth

    OK, the rich will survive but some of the poor are already dying.

    The worst-case methane scenario stands comparable to what CO2 can do. What CO2 will do, under business-as-usual, not in a wild blow-the-doors-off unpleasant surprise,

    Will it stimulate other surprises?

    except that CO2 lasts essentially forever



    Spike on the Climate Progress open thread has just pointed to :
    New materials remove CO2 from smokestacks, tailpipes and even the air

  4. 4
    SecularAnimist says:

    Apologies if I am obtusely missing this in the article, but it would seem to me that the scenario of interest is:

    1. Warming driven by direct anthropogenic GHG emissions causes “natural” methane and carbon emissions, e.g. from thawing permafrost

    2. Those “natural” emissions reach levels which are sufficient to sustain global warming at something like the current (and already dangerous) rates, even if all direct anthropogenic GHG emissions stop

    I would just add that the bottom line of ALL these speculative looks at the various potential “nasty surprises” that may be in store, is to simply reinforce the urgency of rapidly phasing out ALL anthropogenic GHG emissions as quickly as possible. There is, after all, little else that we can do about the problem anyway.

    If your doctor tells you that you need to quit smoking because if you keep smoking you WILL develop emphysema and cancer, does it really make a difference if he adds that you also MIGHT suddenly drop dead from a heart attack?

  5. 5
    Urgelt says:

    NASA warns that there may be a tipping point beyond which an accelerating positive feedback loop scenario might come into play. Under this scenario, most of the clathrate deposits in the arctic (both tundra and shallow continental shelf deposits) could be released into the atmosphere in a fairly short period of time (less than a century), implying a rate of outgassing that makes 100 times present estimated levels a vast underforecast. *That* is the worst case scenario, not an arbitrary 100 times present estimated outgassing rates.

    Is there a tipping point? What is it? Nobody knows. We’re flying blind. That notion ought to give us pause.

    [Response: ‘NASA’ does not make agency statements on scientific issues. Perhaps some NASA scientists have said such a thing, or perhaps they are researching it, but whether it is credible or not has very little to do with it being ‘NASA’. Please provide cites and references for claims like this, especially on a thread that is precisely about exploring the quantitative consequences of this outgassing. – gavin]

  6. 6
    Jim Galasyn says:

    Perhaps transient local warming from methane in the Arctic is a greater threat than the quasi-steady state global effect, accelerating local ice loss and changing ocean and land albedo.

    [Response:But the mixing time for the atmosphere is short, about a year for exchange between the hemispheres and much shorter for mixing along latitude circles, shorter than the thermal equilibration time from rising greenhouse gases. So in general the Earth warms and cools as a whole from GHG concentrations. David]

  7. 7
    wili says:

    Thanks for another thoughtful article on the important subject of Arctic methane feedback. I would like clarification on a couple points.

    Is this article specifically and exclusively about methane from land source?

    Are there other feedbacks that should be considered? One reason I am concerned about even a brief but large increase in methane emissions is that they could push other feedbacks past tipping points. Is this a reasonable concern in this context?

    Again, thanks for a non-dismissive, thoughtful article on this important issue.

    [Response:Shakhova and colleagues are talking about emission from the continental shelf off Siberia, a marine source. David]

  8. 8

    It is OK, economic depression will do it for us (CO2 emissions reduction)…

  9. 9
    Eli Rabett says:

    Eli thinks you are double counting a bit. The water vapor part is only important for strat methane decomposition for example and not all the methane is going to make it there. More important is if it would saturate OH, which would produce a very smoggy world

  10. 10
    Robert Callaghan says:

    Find Out For Yourself!
    Do a google search using the words “methane arctic ozone”
    Make a new tab to google the words “methane nitrous oxides arctic ozone”
    Make another new tab and google “igor arctic torches”
    After another tab google “howarth fracking methane”
    This should keep you busy for quite a while before you realize that carbon credit trading schemes have nothing to do with what we are facing. But, if you are a glutton for punishment you can also google “earthquakes global warming”
    If you really are a masochist, google “anaerobic bacteria arctic methane”
    By now you should realize we are too stupid to live.

  11. 11
    Andrew Newb says:

    Didn’t Pink Floyd write a song about this?

    I think they did…

  12. 12
    John Atkeison says:

    Thanks for this post. This discussion is vitally important for those of us who are trying to greatly expand the number of people who have a sound understanding of the processes that make up what we lay people refer to as “global warming.” My assumption is that if we have more citizens with a better understanding, then we will be able to build more support for really effective measures to address the situation.

    In that spirit, I hope you will take the issues raised so far in these comments very seriously and address them in detail.

  13. 13
    Russell says:

    I expect Monckton & Plimer will invoke Titan’s arctic methane lakes in comparison, and declare its still cold outside, with no kind of atmosphere.

  14. 14
    Jerry McManus says:

    I believe that we are already seeing higher temperature anomalies, compared to the rest of the globe, in the northern latitudes just from increased in CO2.

    I think some of the fear arises from the perception that the positive feedbacks, once started, would take on a life of their own – so to speak – and would not lend themselves to being easily controlled by human countermeasures. The much feared “tipping point”.

    It’s my understanding that is what is meant by “runaway”, not runaway global warming – per se – but runaway feedbacks that result in methane released from the arctic on a scale a full order of magnitude greater than what is proposed by this post.

    Either way, the apparent conclusion that a methane worst case would “only” be twice as bad as business-as-usual CO2 forcing is, to my mind, bad enough.

  15. 15
    Chris R says:

    #9 Eli Rabett,

    “More important is if it would saturate OH, which would produce a very smoggy world.”

    Preindustrial CH4 was around 0.7ppm, current around 1.75ppm, Dr Archer’s suggested increase by a factor of 10 would be 17.5ppm. That’s a 25 fold increase of CH4 from pre-industrial. From table 1 of Schmidt & Shindell 2003 and assoc text: Current CH4 levels imply a 20% decline in OH radicals from pre-industrial, Archer’s metaphorical 10 fold increase of atmospheric CH4 (25 X pre-industrial) would imply* a decline in OH radicals of around 70%.

    Schmidt & Shindell, 2003, Atmospheric composition, radiative forcing, and climate change as a consequence of a massive methane release from gas hydrates.

    *Using scatter plot with trend line in Excel.

  16. 16

    According to this 2007 “science” article we are possibly dead now.

    [Response: There is never a shortage of people saying stupid things, but this is not a ‘science’ article, nor is it a statement related to anything a scientist actually said. – gavin]

  17. 17
    DrTskoul says:

    Why 100 and not 1000? Will not the release become worse with increasing temperature? For the peak concentration isn’t the rate more important than the final amount? How are these bounded to give “worst case scenario”

  18. 18
    Richard Pauli says:

    Thank you for this methane summary. This is such a dramatically emerging issue and we look to RealClimate for the scientifically level-headed blogging analysis.

    Some agreement with #2 Mike Roddy commenting on the unforeseen aspects of climate change. Just yesterday I was honored to attend a Univ Washington seminar given by respected researcher Prof Robert Charlson in which he outlined the historical basis for forced climate change. It was more of a history of science lecture — fascinating to note how swiftly climate research has grown. In a relaxed moment he tossed out the statement ”Who knew the Arctic was going to melt so fast?” My notes are weak here, but he seemed to talk about radical rises in radiative forcing without addressing methane alone. Isn’t 4 or 5 Watts/m2 just from methane quite disturbing?

  19. 19
    Andrew Newb says:

    [Response: There is never a shortage of people saying stupid things, but this is not a ‘science’ article, nor is it a statement related to anything a scientist actually said. – gavin]

    Gavin, to keep silly irrelevent references and ad hominum attacks, may I suggest this link:

    The blog is a non scientific blog, but the flow chart shows the best way to handle ‘scientific’ discussions…I think…but what do I know, I have never been ‘peer reviewed’…


  20. 20
    Icarus says:

    It’s good that we’re trying to use realistic numbers and avoid ‘alarmism’, but I’m mindful of the fact that Arctic methane is just one part of just one positive feedback mechanism. David has higlighted the fact that there are other, larger sources of methane, and of course we know that there are other albedo and carbon cycle feedbacks etc. How far do we have to go before the combined effect of all feedbacks is greater than any mitigation measures we could realistically achieve?

  21. 21
    Doug H says:

    As a non-scientist, it is reassuring that releases of Arctic methane should not force an apocalyptic runaway warming event, although the effects will still have very nasty consequences for our presently comfortable climate. 500ppm – 750ppm still seems like a recipe for societal collapse, even if it pushes back the threat of species extinction. What would be a ‘best case’ scenario for our way of life at 500ppm for a few centuries?

    [reCaptcha: ‘unqualified initabl’ – how appropriate]

  22. 22
    Phil says:

    why pick 100x as the worst case, why not 1,000x? Genuine question, I have no feel for what might be possible.

    [Response:The number was my own pick, as I wrote, of a blow-the-doors-off worst case. Perhaps I lack imagination, maybe it could be worse. But 200 Gton is a lot of carbon. Shakhova et al are claiming 50 Gton C. They argue that a release of that size could come out instantaneously, and if it did, I agree with them, the climate impacts would be immense. I’d written in the previous post that Arctic methane fluxes would have to increase 10 or 100 times before they would start to become significant. The calculation in the second post bore it out, that a factor of 100 would be needed to reach the climate impact of the CO2. But I don’t have a strong reason to draw the limit precisely there. In that sense, in retrospect, describing it as a “worst case” was probably sloppy. Worst I can imagine, and if anyone has a reason to think it could be higher I’d be interested, astonished actually, to hear. David]

  23. 23
    Vergent says:

    Why do you use numbers from a 2007 paper that has been invalidated by more recent studies.

    “Northern soils sequester an estimated 1,672 Pg
    (1 Pg = 1e+15 g) of organic C, 88% of which is stored in
    perennially frozen ground.”

    “This yields an estimated ∼1,600 Pg C
    within gas hydrates associated with subsea permafrost on the
    Arctic Ocean continental shelves.”

    Strong atmospheric chemistry feedback to climate warming
    from Arctic methane emissions
    Ivar S. A. Isaksen et all

    Is not 200Gt a rather conservative worst case, when there are 3,200 Gt of vulnerable carbon in the arctic that we already know about?

    [Response: The Isaksen et al paper is interesting, but their definitions of direct and indirect forcings are a little non-standard and make for a confusing comparison. For instance, they estimate the forcing for 7xCH4 as 0.9 (direct) + 1.7 (indirect) and 1.5 W/m2 (indirect via stratH2O, O3, CO2). The standard IPCC TAR calculation (as done above), gives 2.1 W/m2, and the estimated efficacy of 1.4, implies a total forcing of 2.9 W/m2 (compared to the total 4.1 W/m2). So their estimates are larger (which needs to be understood), but the differences are not going to make a big difference in David’s conclusions. – gavin]

  24. 24
    William P says:

    All the discussion on climate reminds me of a person who has a bullet speeding toward him. He engages in arcane discussion about the type of bullet (hollow point or normal?), its speed measured in nano seconds, the metal composition of the bullet, air density’s ability to slow or speed the bullet, etc.

    What is the point of all the wonderful, scientific point-making? Within certain parameters we know the important facts – the bullet is coming to hit us. Maybe some would say details such as those we discuss might suggest how to mitigate the threat, or accommodate to it. But we also know that is unlikely based on the nature of the threat. Emission control could logically said to be dead. And what kind of adaptation does one do for loss of most agriculture?

    Man and his governments are just waiting to see what happens. That’s the reality. So, the only logical alternative for discussion is survival – is it possible? If yes, how and what should we be doing to accomplish survival for at least some humans?

  25. 25
    michael sweet says:

    Does the response at 7 mean that this article is only about land based release of methane? It seems to me that for a title of “An Arctic methane worst-case scenario” the marine based methane must also be considered. The marine methane is also in the Arctic. As pointed out at 23, this doubles the carbon sequestered. It is possible for the sea to warm faster than the land since heat comes into the Arctic from the Atlantic.

    What is An Arctic methane worst-case scenario that includes the marine methane?

    [Response:Guess I was thinking that 100* Walter would be enough to cover both domains. I think land warms up faster than sea, though, because of the lower heat capacity. David]

  26. 26
    Mark J. Fiore says:

    I really thought all 24 comments were excellent.I am not reassurred.I’ve posted a few times here on the RealClimate comment areas about the threat of methane melting from the ocean floor in the Arctic.I still believe that the potential feedback mechanisms will be worse than described here in the article by Gavin.I am a layman only,Harvard,1982,Boston College Law School, 1987.I read online within the past two weeks that Russian scientists were up in the northern oceans somewhere and they saw tons of hot spots of methane bubbling out from the ocean surface.I think it was in ScienceDaily.The question posed by these scientists was “is this outgassing a normal melting of methane that has been going on for many thousands of years,or,is it an upward tick of significance?”You know what?I still firmly believe that the Earth will stabilise at 1000ppm by the year 2150, and I firmly believe that methane outgassing from both the Arctic seabed and frozen terrestial permafrost will have a huge impact on this number, helping it to rise to 1000 ppm by the year 2150.
    Mark J. Fiore
    Harvard, 1982
    Boston College Law School 1987.
    PS, even if Gavin is correct in his conclusion it is still pretty bad news given the numbers he has come up with.And, I believe that his numbers are very conservative…Gavin, please d’ont ask me to support this as you know I’m just a guy who reads a lot on the internet and posts his gut feelings only.

  27. 27
    Ray Ladbury says:

    CH4 is a sideshow. CO2 is still the big tent.

  28. 28
    Vergent says:

    Thank you for your detailed response to 23 above. But it did not address the issue. The issue is the amount of vulnerable carbon. The known stores of carbon in the permafrost have gone up from “950 Gt of C (Zimov et al. 2006)” Walter et al (2007) to “Northern soils sequester an estimated 1,672 Pg
    (1 Pg = 1e+15 g) of organic C, 88% of which is stored in
    perennially frozen ground [Tarnocai et al., 2009]”. The known stores of hydrate on the Arctic Continental shelves has gone up from:

    “Total amounts of hydrate methane in permafrost soils
    are very poorly known, with estimates ranging from 7.5
    to 400 Gton C (estimates compiled by Gornitz and Fung

    D. Archer, “Methane hydrate stability and anthropogenic climate change”

    cited by you in “Much ado about methane”

    “The ESAS contains an estimated 1400 GT ”

    “” Stubbs, C et all 2010

    Why do you base your arguments on outdated data? Does it improve with age?

    [Response: Updating data is of course fine – but don’t dismiss the substantial uncertainties in any of those numbers. However, and more to the point, what conclusion given above would vary as a function of this adjustment? – gavin]

  29. 29
    Hank Roberts says:

    For Mark Fiore — if you do this Google search: methane laptev

    you’ll find the methane bubbling story asked about here since 2008, and perhaps earlier.

    There have been yearly expeditions.

    The same press release seems to be repeated year after year, so it’s hard to tell what’s news. The AGU heard something about it. A few more searches will find the frequent repeats, no need to repeat it again here.

    We’re all waiting to see the journal article.

  30. 30
    Alan D. Roth says:

    I find it encouraging to see so many comments mentioning possible very nasty surprises ahead. I’ll throw some numbers into the mix here to show that we do indeed have a black swan in the making.

    Ted Shuur ( is one of the leading researchers on carbon in permafrost. He estimates that there are about 1,000 Pg (1 trillion tons) of carbon in the top 3 meters of the continuous Arctic permafrost. Back in 2005, using the NCAR CCSM3 model, Lawrence & Slater (GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L24401, 5 PP., 2005) estimated that about 90% of the continuous permafrost down to the model’s depth of 3.43 meters would thaw this century.

    This was before we saw the disappearance of so much Arctic sea ice that has dramatically increased the thermal energy in the Arctic Ocean. Simulations executed by the NCAR suggest that the warming can penetrate as far as 900 miles inland (over the permafrost). By the way, much of the continuous permafrost is ice-laden (Shuur). It is difficult to say how long the soil would remain wet.

    So we have about 900 billion tons of carbon going into the atmosphere this century. I haven’t seen any mention of this anywhere but perhaps others have. Early on much of it will be in the form of methane. The IPCC dictum to use 25 as the Global Warming Potential for CH4 is ridiculous. Its perturbation lifetime is 12 years so let’s look at what it does early on. A few years ago when I first realized the potential scenario in the Arctic, I asked Dan Lashof, an environmentalist at NRDC who is also a mathematician and was involved with establishing the first round of GWPs in the early ’90s, how strong is CH4 compared to CO2 during CH4’s lifetime? He came up with a number of 100 times stronger when a batch is first emitted. We know that it diminishes to 72 after 20 years. We didn’t graph it but it’s clear that CH4 will be seriously radiating back onto the permafrost at that level before it spreads to lower latitudes. Add to this the thermal energy from the Arctic waters and you have a dangerous concoction.

    Richard Alley found in ice core samples 23 abrupt climate changes over the past 100,000 years (Two Mile Time Machine). The temperature increased 14 to 18 degrees F each time and while many took 10 to 20 years, even more took only 3 years. Even though conditions were different then, we know that abrupt climate change in the Arctic can happen. How long will it be before methane emissions reach a critical mass and, with help from the thermal energy of the Arctic Ocean, create a cascade of rapidly thawing permafrost and rising temperature? Ten years from now? Twenty years?

    David’s worst case scenario is paltry compared to what I believe is a very rational scenario that I’ve presented. I can take it further looking at how the abrupt change in the Arctic would affect global climate. With so much more methane in the atmosphere, OH would be diminished, adding to methane’s lifetime. And when the methane is broken down eventually by OH, we have CO2 with its long life and the more immediate effects of the added water vapor.

    CO2e could be far above 1,000 ppm by the end of the century but by 2050 or even 2030 it could already be untenable. People want to think that somehow we can turn this around but it may already be out of our control. Perhaps that’s why we don’t see anyone putting two and two together. We hear “Ah! There’s always the tundra!” as if that is enough said about this threat. I’m glad to see this discussion started.

    I have a lot more written material on the permafrost and I’ve thought about publishing an article on it. Maybe the time has come.

  31. 31

    ‘Polar Cities’ dubbed ‘Noah’s Arks’ for Humankind in Face of Global Warming and Methane Worst Scenario

  32. 32
    jyyh says:

    Thanks fo this, in addition some sort of description of the atmospheric fate of methane would be nice, i.e. how is the lifetime of the methane calculated, the chemical decomposition of it, and how well-mixed it really is?

  33. 33
    Lewis says:

    Ray – in accepting the proposal that “CO2 is still the big tent” you appear to overlook some differences between anthro- and feedback GHGs.

    One such is the fact that we can, and at some point will, cease emitting anthro-GHGs, but, short of some undefined negative feedback gaining momentum or some other unpublicised auto-limiter, once the feedback CO2e outputs exceed the natural carbon sinks’ capacity of ~43% of anthro CO2, then regardless of our emissions cuts, their interactive mutual acceleration could only be halted by geo-engineering via albedo restoration and sufficient carbon recovery to restore the pre-industrial atmospheric forcing, or by the eventual depletion of all vulnerable carbon banks and ice-masses.

    Feedback permafrost methane is thus far from a sideshow; it is an additional major threat alongside anthro-CO2 that undermines the possibility of mitigating AGW by even a radically swift end to anthro emissions.

    It might be that serious authorities such as Hansen and the head of the UNFCCC secretariat are wrong to declare that goal of a 2.0C ceiling of warming poses unacceptably dangerous climate destabilization, but it seems widely accepted that a peak of 450ppmv CO2 would allow a near-even chance of staying below 2.0C and thereby avoiding the feedbacks taking off with catastrophic effects. Given that this 2.0C goal calculation apparently excludes the ~doubling of warming due to the predictable loss of the ‘sulphate parasol’, and excludes all carbon feedback outputs, it is hard to see how an additional forcing from feedback permafrost methane “comparable to what CO2 can do” can be viewed as anything but calamitous.

    Sideshow it ain’t.



  34. 34
    Hank Roberts says:

    Many answers will be found here:

    “The GOSIC Portal provides convenient, central, one-stop access to data and information identified by the Global Climate Observing System (GCOS), the Global Ocean Observing System (GOOS) and the Global Terrestrial Observing System (GTOS) and their partner programs ….”

  35. 35
    ccpo says:

    Alan, thank you for this. David’s work in these two articles are dangerously conservative. I had e-mail conversations with an ice scientist at NASA back in ’07 or ’08 who said all of this wouldn’t even begin for centuries. He was wrong, and I told him so. I pointed out the systemic pressures and it got me nowhere. The clathrates simply could not melt that fast. But they are. And so David is also incorrect. Can’t prove it, but I do guarantee it, as I have since I began posting here on RC.

    A key component I’ve not seen mentioned enough is the runoff from rivers directly into the Arctic basin. Those waters are heavier than the salty water of the ocean. They should be assumed to flow along the sea floor to some extent… and we don’t need much extent for that for it to begin to warm clathrates, do we?

    And did anyone notice in the defense posted today or yesterday of the findings fom this summer that the cores they drew were **not frozen?**

    We can keep wishing that the science were neat and tidy, that we are not in a new paradigm of humanity, that the planet cannot possibly do what it is, in fact, doing… or we can realize none of this matters. Risk assessment and the precuationary principle say act, act decades ago, act quickly, act organically, act globally, and change *everything.*

    If you love your children.

    And it doesn’t matter if I am wrong: it is still the correct thing to do according to the risk assessment.

    How long we have to see the science so consistently badly underestimate the change before we get error bars to the bad side that reflect the true worst case scenarios, i do not know…. but I pray, figuratively, that it is not long.

    Worst case scenario? How about some real numbers:

    1. Thermokarst laeks increased 300% from the early 2000’s to 2007. What are the odds that has slowed? A not-even-quite-worst-case-scenario would say they will continue to triple decade by decade.

    2. Clathrates? Let us assume the differences between two years ago and this year are consistent and confirmed: That means we went from an amount equal to total oceanic emissions to magnitudes more (tens of meters across to a kilometer across) in just two years. Let’s call it, oh, a doubling only, and call it a decadal doubling, not just two years. One number I found was 7 million tons just from the Siberian shelf/yr a few years ago.

    7×2 =14 x 2 = 21 x 2 = 42 x 2 = 84 x 2 = 168 x 2 = 336 x 2 = 672 x 2 = 1344 x 2 = 2688 x 2 = 5376

    And that’s a fairly good scenario. As Alan points out, the very fast feedback from the full effect of new methane emissions will create larger effects than the averaged numbers indicate, partly because that effect is primarily in the Arctic before mixing has diluted it.

    Not happy.

  36. 36

    Gavin, thanks for taking the time to do this. Thought experiments are always better when properly quantified. Your disclaimer in the first paragraph is very clear, so the context of calling this 100x increase “worst case” should be clear, though perhaps it would be better if you changed the wording given that it’s causing some confusion.

    [Response: This is David’s post, not mine. – gavin]

    “CO2 lasts essentially forever”. I think I know what you mean here but in the context of the previous Much Ado about Methane article with discussion of the difference between atmospheric lifetime of a CO2 molecule vs. lifetime of an increase in concentration, this could also be put more clearly. What I think you mean is that if we get CO2 levels high enough to cause a serious problem, we can’t just stop emitting and hope the concentration will drop in time to make a difference, whereas with methane, it decays fast enough that we need to worry more about the decay products than about methane itself.

    Geoff Beacon #3: the link you point to describes a material that could absorb emissions from a smoke stack, not from the atmosphere. You are still left with the very large elephant of where you store the emissions you’ve captured. Worldwide CO2 emissions amounts to cubic kilometres every year, even if you compress down to a liquid. Even storing 10% is a huge problem, and isn’t helped by capturing the emissions more efficiently. Designing a sufficiently efficient way of storing electricity to make intermittent renewables viable is a much more tractable engineering problem, unless you are in the business of selling coal and don’t know how to do anything else.

    PS: I distinctly recall being able to use sub tags before to spell CO2 correctly in comments. Do I misremember or has this gone away?

  37. 37
    Vergent says:

    [Response: Updating data is of course fine – but don’t dismiss the substantial uncertainties in any of those numbers. However, and more to the point, what conclusion given above would vary as a function of this adjustment? – gavin]

    The scale of the “worst case scenario” is understated by a factor of eight. But why do you insist on arguing from 2007 data???

  38. 38
    Tony O'Brien says:

    Thank you for answering the worries of the doomsayers. For so long we keep hearing how we are just as wrong as the deniers, but you put so much more effort into repeatedly whacking down their bull.

    I still see the Milankovitch cycles as incredibly gentle and the rate of our changes as massive in comparison. I still see us in for a torrid time, not altogether due to climate change, but perhaps even more how nations respond. But that is not an issue for climate science.

    Methane is one of the big issues, and knowing is is unlikely to be as bad as I thought is reassuring.

  39. 39

    #3–Geoff, your link is busted.

  40. 40
    Peter H says:

    So how would this compare with the PETM and what was going on then to cause the effect it did?

    [Response:The PETM was thousands of Gton C from whatever source supplied it, more like our fossil fuel trajectory than like the 100 Gton methane case I explored here. The PETM was also a slower release, taking 10,000 years they say from sediment core chronology. David]

  41. 41
    Anonymous Coward says:

    “small source today relative to tropical wetlands”

    I don’t get this part (which was also mentioned in your previous entry). How is this a meaningful comparison? Isn’t the methane from the tropical wetlands part of a natural cycle (thus net zero), while the thawed permafrost is a net positive source of methane?

    [Response:A small new source is swamped by larger already existing sources, so the relative change in the atmospheric concentration is relatively small. Double the small source, the atmospheric concentration doesn’t double, that was my point. David]

  42. 42
    DrTskoul says:

    Wait a minute..It is exactly the same thing that denialists say about CO2. Anthro- sourses are small compared to the total natural CO2 fluxes.

    [Response:Our rate of mining CO2 from the Earth and putting it in the atmosphere is small compared to the back-and-forth rates of photosynthesis and dissolution/exsolution from the ocean. But our from-the-Earth fluxes are large compared with natural from-the-Earth fluxes from volcanoes, or back into the Earth from chemical weathering forming CaCO3 in sediments. So the CO2 line is fallacious. And for methane, what I wrote was that the Arctic is small compared with low-latitude natural + anthropogenic sources. The anthropogenic sources are now equal to the natural sources, they are not small at all. Just to be clear on that. David]

  43. 43
    Spike says:

    An interesting calculation for which thanks. I note your point that most of the natural methane release comes from the tropics, so a 100 x increase in Arctic emissions would lead to only a x10 increase in natural methane releases overall. But this assumes does it not that a temperature increase that produces this amplification of Arctic methane release has no effect on the rest of the globe, which it surely would do. Would not the increase in temperatures elsewhere on Earth, perhaps coupled with higher rainfall, lead to an increase in temperate and tropical emissions? Add in the increase in anthropogenic emissions from fracking and the dash for gas, where do we get to then?

  44. 44
    DrTskoul says:


    Thank you for the clarification. Agreed.

  45. 45
    Ray Ladbury says:

    CCPO, you forgot to say “Oogabooga”. Ferchrissake. You say the models didn’t predict an observation so they’re wrong about everything? Extrapolating the trend from two cherrypicked years is invalid, and you know it. The fact of the matter is that CH4 releases are still small and have a small effect on warming. It is unlikely that we will see catastrophic release for the simple reason that no such release is evident in the paleoclimate record. What is more, the short lifetime of CH4 + the moderating effect of the oceans and slower feedbacks means that we won’t see a huge spike in warming all at once.

    CO2 remains by far the bigger threat. It contributes and will continue to account for the majority of the warming both now and in the future. Don’t get distracted by sideshows.

    What is more, if there is something vital missing from the models, they will eventually catch up, and we will have more realistic forecasts. If that happens, and the models say we have a problem, then I’ll worry. Until then, you are just jumping at shadows.

  46. 46
    Urgelt says:

    I intended only to cite NASA as a source for worst-case scenarios, not to attribute to NASA any “official” pronouncements, which as we all know would have to pass muster at the political appointee level and rarely do.

    Here is an example – only an example – of the scientific discussion about the potential for massive release of clathrate-stored methane:

    The study was peer-reviewed and was published in Nature in 2008.

    No-one at NASA or any other reputable climatological source that I know about is saying that a massive release of clathrate-stored methane into the atmosphere is a serious risk we’ll face any time soon. But as your article purports to establish the “worst-case scenario” and evaluate its effects, I think it’s a bit strange not to consider “worse” worse-case scenarios being openly discussed in the scientific community than the one you advanced.

  47. 47
    ccpo says:

    Ray, when the facts themselves are so scary, why bother with ooga-booga? What you forgot to say is, “Uh-oh.”

    I note you did not bother trying to debunk those very, very modest numbers. I’ll remind you James Hansen, et al., have posited a potential decadal doubling in melt rates for the Greenland ice sheet. But, in your estimation, that can’t possibly happen in the more biologically and physically complex clathrates and permafost?

    As for the models, they speak for themselves, as you well know. If they were leading the measurments I’m sure we’d all be shocked, happily so, but still shocked – that would be true prediction, wouldn’t it?

    If the models underestimating change by decades and even centuries is not badly underestimating, what is? Is there a better definition of the phrase? This is not a criticism, though you seem to have taken it so. It’s a recognition of their limits as a tool, nothing more. but the dike doesn’t really hold back the waters, the people who built it do. The science isn’t what will save us from our self-inflicted future, it will be the scientists. This is ultimately a human process and at some point we have to act as humans regardless of the various labels each of us carries.

    We will solve our problems by pretending they do not exist or pretending our tools do things they do not. The scientists are getting better at this so the science and the models are, too. But all three are still playing catch up to Mother Nature.

    And do bear in mind, any prescience I have or have not displayed, will or will not display, would not exist without the science produced by the gentlemen here and many others. I offer no disrespect, only one perspective.

    Now, about those numbers.

  48. 48
    Paul says:

    Very interesting article and got me thinking.

    I remember in science class we wanted to see how much sugar we could dissolve into a glass of water and at some point the water becomes saturated and sugar no longer dissolves in the water.

    One tipping point might be if the shallow regions of the oceans become saturated with CO2 and stop dissolving CO2 into it. I’m not sure if this has ever been suggested as a possibility or not, just applying an old science class lesson to an earth system.

    [Response:It happens, but not all of a sudden like the sugar does. As you dissolve more CO2 into seawater, the carbonate ion concentration decreases. Carbonate ion is what buffers the CO2 by reaction CO3(2-) + CO2 + H2O -> 2 HCO3(-). As you lose carbonate ion (as the ocean is acidified), the water’s capacity to absorb more CO2 decreases. David]

  49. 49
    Aaron Lewis says:

    Re inline response in #6
    Then there is a problem with our global methane monitoring system because it shows higher concentrations of methane in north. e.g.

  50. 50
    Aaron Lewis says:

    David is looking at Arctic methane pushing atmospheric GHG concentrations to an equivalent of 750 ppmv of CO2. To which we must add the additional anthropogenic emissions of CO2 over the next few years, which will bring us to a total CO2 equivalent of 850 ppmv (David’s estimate plus Hanson’s estimate of near term anthropogenic CO2 emissions.)

    Even a brief interlude of such warming would give ice sheet collapse a big push, and provide enough heat to liberate carbon feedback from other sources. (Which might occur after peak anthropogenic CO2 emissions.) It would make a mess of agriculture and coastal infrastructure. I do not see that this post provides any comfort what so ever.

    More over, given the changes in Arctic sea ice over the last 50 years, it is likely that less rejected cold brine from sea ice formation is finding its way to the sea floor, and thus permafrost under the various Arctic seas is being exposed to much warmer temperatures. Even a very brief interlude of higher GHG concentrations will give this a big push.

    We have seen lakes on top of Greenland form moulins and fall through kilometers of ice in a matter of hours. The drainage of lakes through permafrost shows the same physics applies to permafrost. The same physics should also apply under the sea. At some temperature, we must expect sea water to penetrate the permafrost under it and displace all of the free methane currently trapped under the permafrost. The formation of undersea thermokarst results in more rapid release of free methane from formations capped by permafrost than the progressive and uniform melting model.

    We can expect significant and rapid Arctic carbon feed back. and thus we should pare back our CO2 emissions, and prepare a planning case for significant releases of Arctic carbon.