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Six Degrees

Filed under: — eric @ 25 November 2007

“Alarmism” is a term that gets bandied about a lot. It is often said that one should not call out “fire” in a crowded building. But it really depends, one might say, on whether the “calling out” is done in such a way as to simultaneously prevent a stampede and prevent anyone getting burned.

This riddle was very much on my mind as I sat down to write my thoughts on Mark Lynas’s book, Six Degrees: Our Future on a Hotter Planet (London: Fourth Estate, 2007). I don’t read much popular science literature, and I doubt I would have read this book if I hadn’t made the mistake of referring to it (in a negative manner) in the comments section of a RealClimate post. I don’t think my error was very grave. What I actually said was that if what I had heard about the book from the press materials were true, then the book was probably alarmist and not worth reading. But I don’t blame the author for asking me to read the book and see for myself. He said that the press (in this case Sunday Times (London)) had misconstrued what he says in the book, and he assured me that is was all based on very careful review of the scientific literature. I was thus both curious and obligated to read the book.

Mark Lynas will no doubt be pleased that I very much like the book. To be sure, it is alarming, but the question of whether it is alarmist is a more difficult one, and I don’t think the answer lies in debating the book. Rather, it lies in looking closely at the underlying science the book builds on. I don’t intend to do that here, but I do think that all climate scientists (particularly those that talk to the public) ought to read this book, and ask themselves a question. I’ll get to that question at the end, after saying a bit more about the book.

Six Degrees, as the title suggests, is comprised of six main chapters (plus an introduction and a conclusion). Each of the main chapters examine what the earth might look like as we raise the planet’s temperature by 1o, 2o, etc. degrees Celsius, based on what the scientific literature has to say about it. Laying out the book this way makes for a good logical progression of ideas, and a fair bit of suspense. Very few people, Lynas says, have got “the slightest idea what two, four or six degrees of average warming actually means in reality, and I’m sure he is right.

In Chapter 1, at 1o, we have predictions of, for example, an annually ice free Arctic ocean. Yes, quite plausible and supported by the literature, and perhaps occurring a little sooner than expected. At 2o, we have, “so whilst southern China can expect more flooding as the two-degree line is approached, the oceanic time lag means that it may take much longer for the rain-bearing summer monsoon to reach the drought-stricken north.” Yes, certainly plausible based on the studies Lynas cites. At 4o, we have “with global sea levels half a meter or more above current levels, [the Egyptian city of] Alexandria’s long lifespan will be drawing to a close. Even in today’s climate, a substantial part of the city lies below sea level, and by the latter part of this century a terminal inundation will have begun. … a rise in sea levels of 50 cm would displace 1.5 million people and cause $35 billion of damage.” Alarmist? Hardly. A 50 cm rise in sea level, is well within the conservative IPCC projections, even for temperature rises less than four degrees.

At 5o and 6o, the book really does start to sound alarmist, with the analogy to Dante’s Inferno – used to good literary effect throughout the book – coming very much to the fore. At five degrees, we have “an entirely new planet is coming into being – one largely unrecognizable from the Earth we know today. At six degrees, “… the pump is primed … not for flourishing palm trees in Alaska, but for the worst of all earthly outcomes: mass extinction.”

Aha, say the skeptics! It is alarmist after all. But is it? Lynas’s reference to the “entirely different planet” actually refers to the fact that at five degrees, the “remaining ice sheets are eventually eliminated from both poles.” That’s entirely true. And unlike in Gore’s discussion of sea level in Inconvenient Truth Lynas does emphasize the long timescales (thousands of years) in this case. Furthermore, there is published research that raises the likelihood of the significant loss of ice sheets at lower temperatures, and Lynas could have claimed certainty of a disappearing Greenland ice sheet in an earlier chapter. That he doesn’t do that is characteristic of the book: it doesn’t tend to go beyond the published literature. This is what Lynas claims at the outset — “all of the material in the book comes from the peer-reviewed scientific literature” – and I think he does an admirable job.

And that brings us back to the question I promised to raise at the beginning, which is this:

If a reading of the published scientific literature paints such a frightening picture of the future as Six Degrees suggests – even while it honestly represents that literature – then are we being too provocative in the way we write our scientific papers? Or are we being too cautious in the way we talk about the implications of the results?

173 Responses to “Six Degrees”

  1. 101

    Chris C (#97) wrote:

    Cody Griffin may be an expert, but he doesn’t appear to up-to-date on what is going on. I found one post by him (based on the same logical fallacies presented above). Back to Lynas….


    I think you are right. I just like digging a little, I guess. Maybe I should have become a geologist.

    I do wish I had a copy of “Six Degrees,” though.

  2. 102

    re Eric’s reply -43
    Eric kindly posted his response on Adamant, where the remarkable iconography at issue may be seen ,and it is there that I have replied to his comment :

  3. 103
    Lawrence Coleman says:

    Re: 63 George Robinson. That’s consistant with what I’ve read as well. I’ve even done the experiment with a tumbler of water filled with water and ice..I thought the ice on top poking above the water might raise the level in the glass change at all in water level!. Then I realised that the ice is less dense than the water so the mass of the ice poking above the rim would be cancelled out by the relative rarefaction of the ice below the surface. As you said..good news for Florida.
    I saw a report by 60 mins..and australian current affairs program about the state of Greenland today. The residents say that things have only been realy apparent in the last 10-12 years. He showed the extent of glacial retreat in only 10 years..very scary! The number of hurricanes and weather borne natural disaters has also made a dramatic leap in the last 10-12 years..what significance you think this time frame holds?

  4. 104
    henning says:

    @Don Condliffe 94
    Is this claim based on anything but a gut feeling that in reality everything is much, much worse?

  5. 105
    Steve Bloom says:

    Re #84: John N-G, I don’t think your statement about the GIS ice being stable since it can’t flow uphill is correct at all. Ice flows under pressure, and enough of a push from above will force it toward the path of least resistance, i.e. toward the coast and thus uphill. I don’t think it’s quite the latest work, but this paper detailing the ice flow is public access and based on the Google Scholar listings seems to be by the leading researchers.

  6. 106
    Shlomi Harpaz says:

    I guess we need to acknowledge that the general public (and most policy maker) will find it hard to fundamentaly change their habits and outlook in view of the threats of GW because of a very clear cognitive dissonance involved.
    Most people don’t want to think the effects of GW through because our society is based on consumption. If we have to use less fossil fuel energy, and make a gradual shift to other energy sources, we will have to lower the general standard of living in the western world.
    So most people hear something about global warming, scare a bit, and then hear something about Britney Spears.
    And if the alarm bells do start ringing inside their heads, it would probably cause a major upheaval in our consumption-based economic system. And what would happen to the Chine’s government if China’s economic boom slows and their people feel they didn’t get the rise in their standard of living they expected?

    So it’s probably going to be harder to realy convince people to act than would be expected from a rationalistic-scientific outlook, and either way- we are probably in for a very nasty ride.

  7. 107
    Steve Bloom says:

    Re #78: Ah, Timo, I see you’re still with us. You know, it’s impolite to not provide a link so that others can easily check up on citations.

    But anyway, Google is my friend. I faintly recalled having seen discussions of that sea level paper floating around the denialosphere some months back, and sure enough there were loads of such hits. Conveniently, though, the very first one was from a non-denialist (Larry Gilman, a science writer with an engineering PhD) who had read the paper and was able to put it in context:

    ‘[The] remarks about the Woppelmann et al. paper seem, if I understand them, to have a twisty spin. I’ve read the paper in question, as well as Munk’s 2002 paper in the Proceedings of the National Academy of Sciences, which enunciated the “20th century sea level enigma” to begin with. Woppelmann et al.’s paper does NOT call into question the reality of anthropogenic (human-caused) global warming. In fact, it takes as given the reality of anthropogenic thermosteric (warming-expansion) and ice-melting sea-level rise. Its resolution of the enigma of excess sea-level rise noted by Munk in 2002 is that the shortfall gets pinched from two directions: (1) since 2002, estimates of the anthropogenic greenhouse contribution to sea-level rise has been upped to 1.4 mm/yr from Munk’s figure of .7 mm/year, and (2) Woppelmann et al.’s GPS recalibration reduces the rise to be explained from 1.8 mm/yr to 1.3 mm/yr. The uncertainty ranges now overlap nicely. Enigma resolved (if Woppelmann et al.’s work is confirmed by others).

    ‘The problem was that anthropogenic sea-level rise didn’t seem to account for observed sea-level rise: Woppelman et al. say that it does, now that we know that anthropogenic rise is _greater_ than we thought before and the total rise is _less_ than we thought before.

    ‘So, no duh, this paper isn’t a disconfirmation of anthropogenic sea-level rise, some kind of “bad news” for people who acknowledge the mainstream scientific view of climate change, sea-level rise, and the like: it’s the opposite. If it holds up, it brings theory into agreement with observation — and does so by correcting the observations, not by trashing the theory.

    ‘Peddling this paper as evidence that anthropogenic climate change is unreal is simply backwards-ass crazy.

    ‘Here it is in Woppelmann et al.’s own words:

    ‘”Munk (2002) stressed that the sum of climate-related contributions to sea-level change was low (0.7 mm/yr) compared to the observations over the last 50–100 years (1.8 mm/yr) by referring to this factor 2 difference as the ‘enigma’ of sea-level change. Since then, the more recent results now indicate a 1 mm/yr contribution from the melting of global land ice reservoirs (Mitrovica et al., 2006), as well as a 0.4 mm/yr contribution from the thermal expansion of the world ocean (Antonov et al., 2005). We show here an exercise of combining GPS and tide gauge results that reduces the global average-level rise to 1.3 mm/yr. This appears to resolve the sea-level enigma.”‘

    Timo, I suppose somewhere out there is a universe with physical laws that would fulfill your fondest wishes by causing all of the climate change uncertainties to break in a helpful direction despite the recent decades of contrary trends. It just seems unlikely that it’s this universe.

  8. 108
    Will says:

    I appreciated this book, as a layman it is difficult to understand what effects are. There are clearly many unknowns I hope the book isnt too optimistic. There should also be a documentry on this subject also.

  9. 109
    Nick Barnes says:

    JCH@93: The GIS is more like a crepe than it is like the WTC. It’s a thousand kilometres from east to west, two thousand kilometres from north to south, a few kilometres thick in the centre, and thinner around the edges.

  10. 110

    Edward Greisch posts:

    [[The Chernobyl accident put out as much radiation as a coal fired plant of the same capacity does in 7 years and 5 months]]

    Thousands of people aren’t dying of thyroid cancer around the average coal-fired power plant, to my knowledge.

  11. 111
    Edward Greisch says:

    “Are we being too provocative or too cautious?” No.

    The problem is that you need an archaeologist beside you to say: “30 previous civilizations collapsed due to lesser climatic shifts.” You need a paleontologist beside the archaeologist to say: “95% of all species went extinct the last time global warming got That bad.” You need a nuclear engineer beside the paleontologist to say: “Nuclear power is safe, cheap and plentiful.” And so on. Or, you could have a synthesizer like Mark Lynas write a book putting all of those voices together for you. You need to announce Mark Lynas’ book on RealClimate. The URL to announce is:
    unless you can reprint the entire text at that URL, or at least the last chapter.

  12. 112
    Nick Gotts says:

    Re #85 (Jim Dukelow) “In Comment #44, Nick Gotts wrote:

    “You might also have mentioned the domestic robots, artificial superintelligences, bases on the moon and Mars, electricity “too cheap to meter” (from nuclear power), and the cure for cancer.”

    The “too cheap too meter” comment was made by Admiral Lewis Strauss in the mid-1950’s to a group of science writers. Strauss was Chairman of the Atomic Energy Commission and was an Admiral by virtue of his work on war production during the Second World War. He was actually a financier, not an engineer or a technical person of any sort.”

    Touche! I admit I used it without knowing the source and background. Thanks for the link.

  13. 113
    Timo Hämeranta says:

    Re #107 Steve Bloom,

    please do not put to my mouth something I haven’t said, or try to interpret my plain English.

    As always, I mainly forward scientific information.

    My personal consideration was:

    “This and other new studies raise numerous new questions, besides sea level rise and oceans heat content, e.g. about water cycle, Antarctica, Greenland & glacier melting, SW & LW radiation penetrating into the oceans, ocean mixing & circulation, etc, etc, etc which all might be more or less wrong in the IPCC models.”

    [edit – stick to the issues]

    btw, the Wöppelmann et al study is available at

  14. 114
    Lynn Vincentnathan says:

    RE #34 & the idea that technology will change and save us.

    Do I have good news for you. The technology is already here and could save us, if only we’d implement it. Please see and Avory Lovins estimates we could reduce our GHGs by at least 75% (below our 1990 levels) without lowering productivity or living standards (using such methods as “tunneling through”).

    Since I’ve already done that and am saving a nice sum of money each year (while actually increasing my living standards), I’m always amazed why people would want to (in effect) pile up their money out on the front lawn and burn it AND thereby contribute to GW. I’m just waiting for someone to manufacture an affordable electric car or plug-in hybrid, so I can drive on my wind-powered electricity. It’s already been invented. In fact EV were invented 100 years ago (ladies preferred them bec they did have to crank them), it’s just that they are so low maintenance and cheap to drive, they’d not be good for the auto or oil businesses. You can see WHO KILLED THE ELECTRIC CAR? –

  15. 115
    Lynn Vincentnathan says:

    RE #46 and climate sensitivity.

    I think the way they figure sensitivity is simply how much warming will we get from X amount of GHGs in the atmosphere, with 2X CO2 of pre-industrial times being the standard for figuring it, & the mean at that level around 3C with a long skinny tail in the positive direction (e.g., there’s a tiny chance it might be higher than 5C or 6C or even greater for a doubling of CO2).

    This sensitivity figure says absolutely nothing about how much GHGs are actually going into the atmosphere — which could really increase a lot (way beyond 2X CO2) once nature starts seriously emitting from frozen permafrost and ocean hydrates due to the warming.

    I think the IPCC & scientists in individual studies do address these slow feedbacks, but I think since a lot of them are unquantifiable & somewhat unpredictable (beyond our general knowledge that heat melts ice) at present, they can’t really add many of these into their equations or calculations. What they can say is it has happened in the past in a really big way; ergo it could happen again.

    I guess what we need is a qualitative (not simply a quantitative) approach, and that is something Mark Lynas provides us (both quan & qual). As an anthropologist I’m into qualitative research — it is not so strong as experiments or surveys for proving cause and effect, but it does get at important knowledge and understanding that experiments and surveys are not able to get at.

  16. 116
    Jim Galasyn says:

    Re Hank in 95, I think you meant to quote Charles Muller instead of me — I just posted that story to generate some discussion.

  17. 117
    J.C.H. says:

    “The GIS is more like a crepe than it is like the WTC. It’s a thousand kilometres from east to west, two thousand kilometres from north to south, a few kilometres thick in the centre, and thinner around the edges. …”

    I wasn’t suggesting that the whole thing will topple like the WTC. I mentioned it because it gives people a visual reference for how tall the GIS is (the WTC towers where around 414 meters tall). The WTC suffered a nonlinear failure, and no structure is immune to one when the attributes that are holding it up are compromised.

    I think the GIS needs a George Irwin. Ice cannot stay a few kilometers in the air with a compromised base. There are bound to be massive collapses. Sections of it many many times larger than ever seen before are going to come crashing down to lower elevations. That would mean more melting and less snow accumulation offset.

  18. 118
    Hank Roberts says:

    Barton, you really should read the well known information on the content of coal fly ash, this is thoroughly documented. There is a significant amount of natural radioactivity in coal.

    Edward, you really should read the same information again, and then carefully read the information on the contents of an operating fission plant and the half-life of the artifical radioisotopes therein.

    No, you won’t get radio-iodine from coal plants. Yes, much else.

    Guys, this is serious stuff, Gavin’s repeatedly asked it be taken elsewhere, there’s nothing to argue about if you read the good established science and stay with it.

    Confused statements lead to pointless arguments about this issue.
    It’s real. It’s elsewhere.

  19. 119
    J.S. McIntyre says:

    Re 34 (and 36 & 44)

    Joe wrote: “One challenge for those who worry a lot about *eventual* catastrophic conditions is the mistake of thinking technology won’t change over the next decade, let alone the next century. It will change *dramatically* and is likely to significantly reduce risks in many areas.”



    Antibiotics were considered a major breakthrough that was going to improve health tremendously. Now, decades later, we’re faced with the very real concern of antibiotic-resistant bacteria from overuse/misuse of the very “breakthrough” that was going to cure our ills. We left evolution out of the equation.

    Plastics were going to make our lives easier; now our world is overrun with them to the point where we find traces of plastic on literally every level of the food chain. (For details, check out Alan Wiesman’s ‘The World Without Us’, an excellent book that, just as Eric observes with Lynas’ book, relies strictly upon the science/evidence that exists to discuss its subject, which is the effects of humanity’s ‘footprint’ upon the biosphere.)

    Fission-driven nuclear power was a stepping stone on our way to fusion, but decades after this claim was made (by many of the same people who proposed using nuclear devices to create a second Panama Canal in the 50s – weren’t we lucky they didn’t follow through on that bit of brilliance?) fusion seems as far away as ever and in the meantime, as discussed exhaustively elsewhere, the remains of the Fission programs have left numerous, virtually indelible scars upon the topography and in the biology of the planet.

    Oil was going to (and did!) reduce the expenditure of energy to create energy on a huge scale. But now, well over 150 years into the age of oil, its effects can be traced everywhere on the planet and within the biosphere in terms of toxins that pollute our water, food and air. And, of course, we have the discharge of CO2, a disturbing byproduct that may change forever the manner in which humanity will be able to exist on this planet.

    My point, of course, is the fallacy of saying “we’ll develop technologies to deal with the problem” ignores the understanding that the implementation of technology is often about trade-offs: to gain an advantage/comfort/relief, what disadvantage/pain/loss must we be willing to accept? This is a question we must constantly ask ourselves moving forward, because when you really look at the problem we face as a species, it is not solely about Global Warming. AGW is a symptom of a much larger problem, albeit a symptom of something that has all the characteristics of a malady that could cause us great, even mortal harm in the long run.

    Don’t get me wrong. I am not a Luddite by any stretch: I love technology; I derive benefits aplenty from it both at home and at work. Technology has saved the lives of people close to me. But there is a world of difference, IMHO, between understanding the benefits derived from technology, and blithely believing that whatever happens, we’ll ‘tech’ our way out of it. There are no guarantees this will happen. If you believe otherwise, I would recommend you revisit the claims made at the 1938 World’s Fair in New York regarding what the world would be like in 50 years.

    Finally, while I haven’t read Lynas’ book yet, given Eric’s review I would recommend Wiesman’s book as a companion read, given its emphasis on the true scope of mankind’s footprint upon the biosphere. IMHO, it helps give a better perspective of the true magnitude of the problems we’re facing as a species. This isn’t just about getting GHGs under control, though that is a huge part of it. It’s about reversing a series of trend that is slowly but inexorably instituting changes on a global scale that will likely cause huge, if not insurmountable problems for our descendants.

  20. 120
    J.S. McIntyre says:

    re 87

    “The idea that a nuclear winter will follow nuclear war is pretty firmly ingrained in the public mind, despite the fact that nobody really knows what would happen.”

    You know, I always sort of looked at the idea of a Nuclear Winter as insult following injury.

    I think one could study the data regarding the aftereffects of Hiroshima and Nagisaki and extrapolate accordingly for higher yields and multiple detonations on an international scale.

    Whether the nuclear winter would follow would likely be inconsequential in relation to the damage to the biospehere.

  21. 121

    Re 87;
    “there also needs to be an idea of very blatant and graphic results of global warming to help people get a handle on the possible consequences… as [with] the “darkness and winter throughout the whole world for decades” nuclear winter message.”

    If disarmament is too important to be predicated on mythology, how is cogent climate policy to arise from the deliberate confusion of computer modelin and pop artin this case.

    “Nuclear winter”‘s deserved notoriety- notorious is what Kerry Emmanuel called the studies in _Nature_ arose from lack of transparency in peer review- a failure that the IPCC has taken considerable pains to avoid.

    In the nuclear winter case, the most extreme and unrealistic parametrization- a sustained optical depth of 20 became the basis for the popularized version of the hypothesis- an image of the Pale Blue Dot airbrushed flat black. Lynas quaint cut of submerged London belongs to the same genre.

  22. 122
    Nick Gotts says:

    RE #87, 121 (ME, Russell Seitz on nuclear winter)

    ME, Russell, take a look at the papers linked from

    “Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences”
    Alan Robock, Luke Oman, and Georgiy L. Stenchikov (2007) J. Geophys. Res,112, D13107, doi:2006JD008235

    This indicates that global nuclear war would have utterly devastating atmospheric and climatic effects – global dimming and cooling (to mean temperatures below that at the LGM 18000 years ago)and a sharp drop in precipitation, largely wiping out agricultural production for perhaps a decade, plus extensive destruction of the ozone layer. Still, at least we wouldn’t need to worry about AGW any more.

  23. 123
    Richard Ordway says:

    Hmmm, Oh boy…did we just reach an historic paradynm shift on GW in the scientific peer-review, publishing community?

    Science Journal reports that 50 top expert publishing scientists had a meeting on geoengineering and agreed to do something that was previously “taboo”. Oh, boy do I smell a can of worms.

  24. 124

    Nick re 122

    Alan is still trying to unload the remainders of his 1987 ‘Nuclear Winter’ book- Please note that the revisionisim extends to downshifting the optical depth by eighteen powers of e. And that instead of temperatures falling to twenty three below zero, the delta T in modern 3-d GCM’s is in the low single digits– a few hundred degree days do not a winter make.

    Though the original advocates remain in ,pardon the expression, denial, the deflation of what CarlSagan styled his ” Apocalyptic rediction’ began with Stephen Schneider’s 1986 _Foreign Affairs_ article ,”Nuclear Winter’ reappraised. I suggest you may also find these links edifying :

    If you believe it trivial to achieve and sustain man made stratospheric aerosols of significant optical depth, I suggest you nominate Paul Crutzen for another Nobel- to be shared with the surviving Alvarez, because at another level of polemic gamesmanship, ‘ nuclear winter’ was the freeze movements attempt to run off with the KT extinction hypothesis.

    [Response: I’m not sure what point Russell is trying to make with the repeated harping on the history of attempts to understand nuclear winter, but to me the nuclear winter business seems to be a good example of the proper operation of science. Somebody points out a possible catastrophe, does the quick back of the envelope calculations to show they’re not crazy to be worried about such things, publishes it. Other people get to work, examine it in more detail, and the problem starts to look less alarming. A century of work on global warming, in contrast, has not made the problem go away. The problem looks as alarming as ever and the science just gets firmer. Also, one shouldn’t be too snide about the value of bold and partly wrong hypotheses. A lot of good work on soot and KT extinction mechanisms was stimulated by the nuclear winter paper. And one should be a bit more humble in the face of the big ideas Carl Sagan introduced into the subject of planetary science — the Faint Young Sun, the greenhouse explanation of the temperature of Venus, the discovery of the Early Mars hydrological system, and many more. I wish my right ideas could be half so important as Sagan’s wrong or partially wrong ones. –raypierre]

  25. 125


    By an odd coincidence , “devastating atmospheric and climatic effects – global dimming and cooling (to mean temperatures below that at the LGM 18000 years ago)and a sharp drop in precipitation, largely wiping out agricultural production” were all predicted as the immediate consequences of the Kuwait ZOil Fires by none other that Carl Sagan, when asked on_ Nightline_ if the fires effects would be analgous to those of a nuclear war.

    It didn’t happen.

  26. 126

    [[You need a nuclear engineer beside the paleontologist to say: “Nuclear power is safe, cheap and plentiful.”]]

    Not telling the truth is counterproductive. That’s part of the reason the nuclear industry generated so much opposition the last time — their tendency to completely blow off any potential problems and make airy statements like the above.

  27. 127

    Hank Roberts writes, inexplicably:

    [[Barton, you really should read the well known information on the content of coal fly ash, this is thoroughly documented. There is a significant amount of natural radioactivity in coal.]]

    And where, precisely, did I say that there wasn’t? Were you under the impression I was defending coal? My whole point was that I don’t buy the simplistic “It must be either coal or nuclear” dichotomy that Greisch and others keep throwing at us.

  28. 128

    [[In the nuclear winter case, the most extreme and unrealistic parametrization- a sustained optical depth of 20 became the basis for the popularized version of the hypothesis- an image of the Pale Blue Dot airbrushed flat black. Lynas quaint cut of submerged London belongs to the same genre.]]

    Schneider’s Nuclear Autumn paper also had flaws, like plume heights that were off by a factor of three. Nuclear winter wasn’t ever definitively disproven. The idea that it was is a pop-sci-culture myth.

  29. 129

    (#105 Steve Bloom) I’ve no dispute with the proposition that the outspreading and subsequent marginal melting of the Greenland Ice Sheet would accelerate with a lubricated base, and there’s evidence that this is happening. However, the time scale for this is centuries, according to existing physical and modeling evidence.

    I presume that one role of the Greenland topography is to provide a self-limiting mechanism for rapid ice sheet collapse. As the depth of the ice declines, the outward pressure that produces the flow of ice decreases, at least until rebound takes place. Such a moderating mechanism is not present on an glacier with an underlying outward-sloping surface. I’m in no sense an expert on this, though.

    To my knowledge, nobody has proposed a decade-scale mechanism for catastrophic failure of the Greenland Ice Sheet, let alone a mechanism that would suddenly produce tens of millions of refugees. The West Antarctic Ice Sheet, being considerably less grounded, is presumably more subject to catastrophic failure, but farther down the road.

    That said, the uncertainty regarding unstable ice sheets is one of the big unknowns that make attempting to identify a specific “safe” level for CO2 rise a very dangerous proposition.

  30. 130
    Hank Roberts says:

    Barton, I was reacting to this exchange, you both compared incomparables. I’m a nitpicker, I do it evenhandedly I hope. You both have good points, these mistakes detract from discussion.

    Here’s where y’all departed from the facts, one from each:

    >[[The Chernobyl accident put out as much radiation as a coal fired >plant of the same capacity does in 7 years and 5 months]]

    BUT the isotopes are different. Quoting from the linked article,

    “All studies … of radioactive elements from coal combustion conclude that the perturbation of natural background dose levels is almost negligible…. these isotopes over 150 or 250 years could pose a significant future ecological burden …”

    Radiation from coal smoke isn’t comparable to a nuclear plant leak.

    > Thousands of people aren’t dying of thyroid cancer around the
    > average coal-fired power plant, to my knowledge.

    BUT the isotopes are different. That can’t happen.

    Coal has no Iodine-131, no more than it has any Carbon-14. Spencer Weart explains how knowing this helped discover actual evidence of the greenhouse effect.

    Radiation from a nuclear plant leak isn’t comparable to coal smoke.

    And you can check the number of thyroid cases, it’s closely watched.

    —-> Yes, y’all both have good points. I’m urging you always to check, stay with the facts, and cite to sources.

  31. 131
    Bill Sneed says:

    Re #11 & the socio-economic impacts of sea level rise. An interesting study by G. McGranahan, D. Balk, and B. Anderson can be found in Environment & Urbanization Vol.19 No.1, April 2007,
    “The rising tide: assessing the risks of climate change and human settlement in low elevation coastal zones.”

  32. 132
    Lynn Vincentnathan says:

    If I recall, Mark Lynas also brings up deadly hydrogen sulfide outgassing at 6C (eventually as it plays out over a long time), and I’ve read about this happening during the end-Permian, some 251 mya — the final death blow, after much life had already been wiped out by extreme global warming and its effects.

    It would be good if the RC scientists could at least explain how this might happen eventually (after, say, 100s or 1000s or 10,000s of years (I have little sense of geological timescales)) IF the BAU+very worst case scenario totally plays out. I’m assuming this is at least a small possibility, if not very likely.

  33. 133
    mark s says:

    Hi all,

    thanks 4 the review Eric, i’ve been waiting for RC’s take on this since i bought the book in the UK, just after its release date (Jan or Feb?).

    I thought it was alarming but not alarmist, and contained many bits of valid info i knew to be correct and in context. I’m glad my instincts were correct :-)

    I think Lynas has shown that well-informed journalists (who tend to get a kicking on RC, normally!) have a crucial role in getting the ‘new’ (more alarming) message across to the public.

    Although AR4 did publish a similiar (deg by deg) table later in the year, the fact that Mark Lynas got there first is concerning.

    I don’t know if i’m making myself clear, but we all know how useful a deg-by-deg guide is, for public understanding… so why have we waited for the admirable Lynas to do it? I’d far prefer to have heard it from someone who i didn’t have to wait 9 months to validate, ie the AAAS or the Royal Society etc, etc.

    Thanks anyway, i can hand the book round to my friends with greater confidence, having read this thread.

    Thank u RC

    Mark S

  34. 134
    Nick Barnes says:

    John Nielsen-Gammon@129: I agree, the lack of really good dynamic ice-sheet models means we have a major predictive shortfall here. I’ve asked on previous RC threads who, where, is modelling the dynamics of ice-sheet melting, and not got much of a response. I’m sure there are a bunch of scientists working very hard on this, but I don’t know who they are or what they are concluding.

    On mechanisms for catastrophic GIS collapse, consider that Greenland without the ice sheet would be a set of islands. Is it possible for sea water to intrude into the basin, following some marked peripheral melt and thinning? If so, that’s exactly the sort of process which I could imagine involving positive feedback. This is, I think, broadly similar to one of the proposed mechanisms for WAIS collapse: an accelerating retreat of the grounding line, into the interior of the ice sheet. I read an old paper last month, can’t find the cite, about evidence of a previous rapid retreat of the WAIS. In the case of the WAIS, the grounding lines from Ross and Filchner-Ronne would meet in the middle. (My Hollywood version of this has the whole remaining ice sheet tearing itself away from the bedrock, possibly with a huge sucking sound, to float on the new Antarctic Sea, and global sea-level rises by several metres in the course of a few *days*. I’m available for writers-strike-busting.)
    WAIS is also in a basin, of sorts: the central base of the ice sheet is much further below sea-level than anywhere on its perimeter. The main relevant difference between GIS and WAIS boundary conditions seems not to be the bedrock topography but the fact that the WAIS meets the sea in big ice shelves, whereas the GIS meets the sea in a number of somewhat smaller glaciers. But I’m just an amateur here.

  35. 135

    If ,as Barton writes “Nuclear winter wasn’t ever definitively disproven,” it is because semantic aggression has given way to denial encompassing even how the debate began– with Sagan declaring in Foreign Affairs that :

    “Apocalyptic predictions require,if they are to be taken seriously , higher standards of evidence than do other matters where the stakes are not so great.”

    History is full of prophets of doom who fail to deliver.

    [Response: Possibly because they were listened to and actions taken to avoid the worst? -gavin]

    [Response: History is also full of Neville Chamberlains offering reassurances that there’s nothing to worry about. No problems are looming. Peace for our time. Kick back and enjoy business as usual. –raypierre]

  36. 136
    Jeffrey Davis says:

    Did the IPCC really say “the “radiative forcing” from CO2 rose by 20 percent between 1995 and 2005”? This doesn’t sound like something “they” would say. I don’t recall reading it in the AR4 (but that doesn’t mean much). I find it hard to believe it is there some place. Perhaps they said the rate of change of the increase of radiative forcing increased by 20%?

    Does anyone recall seeing this supposed statement by the IPCC? Or is Monckton making things up?

    page 3

    “For the 1995 to 2005 decade, the growth rate of CO2 in the atmosphere was 1.9ppm yr-1 and the CO2 RF increased by 20%”

  37. 137
    David B. Benson says:

    Lynn Vincentnathan (132) — Where is the H2S supposed to originate? Volcanoes, so by inference also flood basalt formation, produce H2S. The assmption is that the PT event, temporally associated with the formation of the Siberian Traps, was due to that outpouring of basalts.

    The other source of H2S that I know about is sour gas, that is, natural gas with up to 28% hydrogen sulfide. AFAIK, there is little sulfur in peat bogs or under permafrost, but I could be wrong about this…

  38. 138
    Hank Roberts says:

    “People ask me to predict the future, when all I want to do is prevent it.” — Ray Bradbury

  39. 139
    Jim Galasyn says:

    World must fix climate in less than 10 years -UNDP

    BRASILIA, Nov 27 (Reuters) – Unless the international community agrees to cut carbon emissions by half over the next generation, climate change is likely to cause large-scale human and economic setbacks and irreversible ecological catastrophes, a U.N. report said on Tuesday.

    The U.N. Human Development Report issued one of the strongest warnings yet of the lasting impact of climate change on living standards and a strong call for urgent collective action.

    “We could be on the verge of seeing human development reverse for the first time in 30 years,” Kevin Watkins, lead author of the report, told Reuters.

    The report, presented in Brasilia on Tuesday, sets targets and a road map to reduce carbon emissions before a U.N. climate summit next month in Bali, Indonesia.

    Emissions of carbon dioxide and other greenhouse gases into the atmosphere help trap heat and lead to global warming.

    “The message for Bali is the world cannot afford to wait. It has less than a decade to change course,” said Watkins, a senior research fellow at Britain’s Oxford University. …

  40. 140
    David B. Benson says:

    Corecting and finishing comment #136 —

    Sulfur is present in peat bogs from 0.29 to 4.21 per cent.

    The overall reaction was fast, with H2S half-lives on the order of several hours. The results suggest that DOM may chemically reoxidize H2S in organic rich soils and sediments at significant rates.

    DOM = Dissolved Organic Matter

    Methoxylated aromatic compounds are likely a major source of methyl groups for this methylation of hydrogen sulfide, since they are important degradation products of the abundant biopolymer lignin.

    Apologies for the lack of references, but web trawiling on the search phrase ‘hydrogen sulfide peat bogs’ bings up the sources as items 1, 2 and 6.

  41. 141
    Lynn Vincentnathan says:

    RE #137 & 140, from what I read (& I sure I’m getting it wrong), the H2S kill off came in the very advanced stage of warming during the end-Permian. It came from the oceans, I believe, and it was created by anoxic conditions, and I think the CH4 as it gets released from hydrates, if conditions are anoxic, it turns into H2S. There’re some microbes that change it (I think). And apparently the hypothesis is that great outgassing occured and went over portions of the land, as well, which almost instantly killed most plants and animals in its path (both in the oceans and over portions of land).

    I’m sure I’ve gotten this wrong, so that’s why I was hoping someone would explain it to me.

    Here, I just did a google search from 2003, but I also read something from 2006?):

  42. 142

    Had RC existed in 1983, I hope the Freeze Movement would have had a harder time turning Crutzen & Birks aptly titled ‘Twilight At Noon’ into the apocalypse of biblical proportions that Sagan merchandised on late night TV

    RC needs to recall that the polemic abuse of global systems models is as old as the Club Of Rome Report, and will likely go on for as long as advertising agencies endure –in post-Cold War perspective , ‘nuclear winter’ may rank as a bad joke played at the expense of the credibility of climate modeling on the eve of the global warming debate. Sure, they were trying to save the world, but since the joke equated even tactical weapons with ” the extinction of homo sapiens” at a time when NATO ‘s conventional forces were severely overmatched, not all SALT era diplomats found it funny.

  43. 143

    Lynn Vincentnathan (#132) wrote:

    If I recall, Mark Lynas also brings up deadly hydrogen sulfide outgassing at 6C (eventually as it plays out over a long time), and I’ve read about this happening during the end-Permian, some 251 mya — the final death blow, after much life had already been wiped out by extreme global warming and its effects.

    If I remember correctly, Peter Ward seems to believe that four out of the five major extinctions involved this mechanism. It is certainly something I am interested in — and have done some reading on. I also know of an online book which is specifically devoted to that topic. Overhyped title, but the contents seemed professional. I will look it up and get back to you on it — and include it in this thread as I know it is of interest to a number of the people here.

    Personally, I don’t know to what extent we might be threatened by that sort of thing (will we get above 1000 ppm?) but I find it fascinating from a paleoclimatological perspective. Of course I wouldn’t want anyone to learn about it up close though.


    Incidentally, my apologies.

    Your interpretation of an almost ensured slide from 3 C to 6 C does actually appear to be a part of this book. Personally I am not sure how realistic this is. But it is part of the video the authors did for the book — where they lean heavily (too heavily?) on the carbon feedback. Regardless, judging from the video and what Eric has to say, I think the book will be fascinating.

  44. 144
    Fernando Magyar says:

    Re # 42,
    Gavin, While I agree with the probable intent of your statement,

    You have to admit that a person walking away from a fire with an empty can smelling of kerosene and a book of matches with a burnt match, still does not allow you to come to the logical conclusion that said person started a fire. Though the circumstantial evidence in this example is very strong you would need the security video camera tape of the person pouring the kerosene and actually lighting the match to it to support the logic of your initial statement. To be clear I am sure that you have the tape already in your possession so the culpability of the arsonist is not in any serious doubt, just not by the logic of your original statement. Please forgive my quibble, cheers!

    [Response: Actually, that is just more circumstantial evidence. Is the picture truly clear enough to unequivocally identify the arsonist? Maybe it was tampered with, maybe it’s from a previous fire he set etc…. The same is true in the climate business – we only ever have (more and more convincing) circumstantial evidence – there is never going to be absolute proof – only in pure mathematics does this exist. – gavin]

  45. 145
    David B. Benson says:

    Lynn Vincentnathan (141) — Thank you for the link. Here is one from 2006

    regarding the role of manganese(III). The link below may help explain what you have in mind regarding H2S from the ocean.

  46. 146
    Jim Galasyn says:

    Re the source of H2S in 141, as I understand it, Lynn is correct. There’s a layer of microbes that consume the H2S produced by the deeper anaerobic organisms — this layer is the redox boundary. As the oceans warm, they become increasingly anoxic, and in the PT extinction theory, the redox boundary rises to the surface. All aerobic organisms in the oceans die, and excess H2S kills life on land as well. Then it attacks the ozone layer.

    Here’s a good story from last year’s SciAm:

    Impact from the Deep

  47. 147


    Sorry about the formatting on 143 — obviously only the first paragraph was yours.

    The book I mentioned is specifically on the methane catastrophe. The problem with hydrogen sulfide, however, receives considerable attention in several chapters. In the current form of this theory is not so much a problem in the open ocean but along the continental plates. I find this much more realistic — and would expect it to have much of the same effect insofar as life, whether in the ocean or on land, tends to prefer to live near the coasts.

    Likewise, rapid warming where the land warms at a considerably higher rate will tend to produce the sort of circulation which encourages such algae blooms along the continental plate, creating anoxic conditions as well as, I believe, warming the methane hydrates we have found or have infered to exist along these areas. And as someone here has pointed out could be exacerbated by the modern use of fertilizer insofar as its river runoff encourages the production of algae blooms that result in dead zones.

    Anyway, here is the book with the over-the-top title, but in my view, quite respectable content — by Dan Dorritie. Likew Peter Ward, Dan Dorrite is a paleoclimatologist.

    Killer in Our Midst
    Methane Catastrophes in Earth’s Past . . . and Near Future?
    Dan Dorritie

  48. 148
    Lynn Vincentnathan says:

    Here’s a better article re the H2S kill off, “Global Warming Led To Atmospheric Hydrogen Sulfide And Permian Extinction,” ScienceDaily (Mar. 1, 2005). See:

    I guess my concern is not that this would happen anytime soon, even within thousands of years, but that our triggering of a hysteresis warming event for over 100,000 years, if we do push it to 6C (via slow feedback), could result in such a die off.

    From a moral perspective it doesn’t matter when our actions of today finally result in harm to people and other life forms, but whether they might do so (eventually). Knowing that our actions today (over our lifetimes) might result in such harms puts a serious moral duty on us to cease and desist (i.e. reduce our GHG as much as possible). Re denialists saying they don’t believe AGW is happening or is/will be harmful or this H2S thing might happen doesn’t cut the moral mustard, once we’ve been informed of this possibility from scientists.

    I suppose everytime we drive we pump some local pollutants into the air that might harm people, but contributing to an extremely huge die off of life around the world (and some biologists tell us the 6th great extinction event is already underway), when we could fairly easily reduce our GHG and do so mostly cost-effectively seems disproportionately morally offensive.

  49. 149

    David B. Benson (#145) wrote:

    The link below may help explain what you have in mind regarding H2S from the ocean.


    They don’t give you the exact location. Neither does Peter Ward.

    But that is right around Walvis Bay. There is a UN outpost in the northern part of the picture though you can’t see it at that resolution. Try 23 degrees 19 minutes South by 14 degrees 29 minutes East. I scowered the coastline looking for the location in Google Earth some time ago. Didn’t keep the coordinates or even the name of the Bay, but I remembered a geologic formation, the shape of the coastline and the UN post — and so I was able to find it again. At one point I was able to pick out what looked like the hydrogen sulfide cloud in the picture you linked to.


    I wouldn’t care if it happened four thousand years from now. Might as well be the next ten years — from my perspective.

  50. 150
    Nick Gotts says:

    RE #71 (Joe Duck) “Nick I don’t accept the premise that disaster is looming”

    Joe, a disaster is unlikely to *happen* in the next 10 years, but when we take into account the multiple lags in the system: taking decisions at an international level, devising and passing laws, building energy-saving and low-carbon power stations, buildings, transport etc., and the lags in the climate system itself – then even at the mild end of the IPCCs AR4 projections, we could well have only 10 years to avoid a disaster further in the future.

    “10 years will bring a lot of technology improvements, as well as much better climate modelling computer power. Conscious computing, which is 10-20 years away, may bring a climate model that actually has a high level of real-time predictive power. This would settle a lot of the key questions regarding ice changes and the pesky lag issues surrounding CO2 and temperature, which make good projectioons of even a few year time horizon impossible for the current models.”

    As for what technology improvements 10 years will bring, the only specific one you mention is more climate modelling computing power. Yes, the models will get better, but if you look at the models of 10 years ago, I’d say the improvements are real but certainly not revolutionary. No reason I am aware of to expect anything different in the next 10. As for “conscious computing” being “10 to 20 years away”, on what do you base that opinion? I worked on AI in the 1980s and 1990s, and have continued to follow it; I see no prospect of anything you could reasonably call conscious computing in the next few decades – going on the pace of progress over the last 50.