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The debate is just beginning — on the Cretaceous!

Filed under: — raypierre @ 23 January 2008

Most of us who are involved in research related to climate change have been asked at one time or another to participate in public debates against skeptics of one sort or another. Some of us have even been cajoled into accepting. In the pre-YouTube days, I did one against the then-head of the American Petroleum institute at the U. of Chicago law school. Gavin did an infamous one against Crichton and company. People are always demanding that Al Gore debate somebody or other. Both Dave Archer and I have been asked to debate Dennis Avery (of “Unstoppable Global Warming” fame) on TV or radio more than once — and declined. It’s a no win situation. If you accept you give the appearance that these skeptics have something to say that’s actually worth debating about — and give their bogus ideas more publicity. If you decline there are all sorts of squawks that “X won’t debate!” or implications that scientists have declared “the debate” (whatever that is supposed to mean) prematurely closed when in fact it is “just beginning.”

Scientists tend to react badly to demands like this in part because the word “debate” is a rather poor description of the way disagreements get hashed out in science. John Ziman has a good discussion of the extent to which scientific questions are ‘debatable’ here (pdf). In a lawyerly debate, it is fair game for each side to pick and choose whatever argument has the most persuasive force with the audience, jury or judge, without any obligation to consider the force of counter-arguments except insofar as they affect one’s defense against the opponent. Science, in contrast, is a deliberative, cooperative, yet still competitive enterprise, where each side is duty bound to fairly consider all arguments and data that bear on the matter at hand. This is not to say that scientific disputes are necessarily dispassionate or orderly. Indeed, I’ve seen near-fistfights break out over things like the Snowball Earth and the interpretation of Neoproterozoic carbon isotope excursions.

The repeated challenges to debate are probably meant to imply that scientists — and their supporters, including Al Gore — are fixed in their ideas, unreceptive to the new and challenging, and unwilling to defend their ideas in public. This picture is hard to square with how scientists actually behave among themselves. It is not that scientists don’t debate, dispute, disagree about matters related to climate. All those things happen, but not on the subjects that skeptics like Inhofe or Fred Singer or Dennis Avery would like to debate (like whether global warming is mainly caused by CO2 or solar variability, or whether the IPCC warming forecasts represent a credible threat.). Those sorts of things are indeed considered settled science by serious climate scientists. Then, too, scientists are justifiably wary of being drawn into staged debates on such diffuse, ill-defined and largely meaningless topics as whether global warming counts as a “crisis.” In the war of the sound bites, the people who feel free to lie and distort can always win. David Mamet made this point eloquently in Bambi vs. Godzilla. A debate like that is not any kind of debate in the sense understood by scientists.

In fact scientists are probing theories and conceptions all the time, trying to break them. The best way to become famous is to overturn established wisdom, so scientists look hard all the time for opportunities to do this. The problem of Hothouse climate states like the Cretaceous and Eocene is a case in point.

The Cretaceous is the time period from 145 million years ago up to the demise of the dinosaurs about 65 million years ago. The Eocene is a more recent period, from 56 million years ago to 34 million years ago. In between is the Paleocene, which is generally somewhat cooler than the late Cretaceous or mid Eocene. It has long been known that the polar climate — particularly the Arctic climate — was very different from today’s. Many lines of evidence indicate temperatures well above freezing, with little or no permanent land ice and infrequent or absent sea ice. Lemurs could live in Spitzbergen, and crocodiles on Hudson Bay, to name a few examples. Most evidence also points to an absence of ice in Antarctica as well. These Hothouse (or Super Greenhouse) climates have much warmer polar regions than is the case for today’s climate, and winters were evidently very mild. These hothouse climates are idealized as having been almost completely free of significant ice sheets on land and sea ice cover in the ocean. Hothouse climates pose a challenge to our understanding of climate in general, but more particularly they serve as a critical clue as to what surprises a high-CO2 world might have in store for us.

This is so because, at present, the only viable theory for Hothouse climates is that they come about as a result of elevated CO2 concentrations, which in turn are due to long term changes in the Earth’s carbon cycle. The CO2 theory has many problems, some of which I’ll discuss below, but no theory without elevated CO2 has been able to even come close to accounting for the Hothouse states. These climates would be just dandy as a natural test of the Earth’s sensitivity to long lived greenhouse gas concentrations were it not for one nasty fact: it is very, very difficult to get an accurate idea of how high the CO2 concentrations were so far back in time (see Crowley and Berner or Broadly Misleading on RC). For example, estimates for the Eocene range from values similar to modern CO2 concentrations all the way up to 15 times pre-industrial CO2. This unpleasantly large range represents uncertainties in the proxies used to estimate CO2 in the distant past. Various general circulation models can achieve largely ice-free polar conditions with CO2 between 4 and 8 times present concentrations, though even at those levels there are difficulties in accounting for the mildness of the winters. And up until recently it was thought that the tropical temperatures in such simulations were far warmer than reality — but more about that anon.

In the past few years there has been a real shake-up in the conception of what hothouse climates are like. First, it was found that the Tropical regions in hothouse climates are not tightly thermostatted as had been previously thought. Prior indications of a cool tropics turned out to be an artifact of alteration of the chemistry of marine sediments after they were deposited — a nightmare known as diagenesis to paleoceanographers. The tropics are actually quite a bit warmer than today’s tropics. For example, the Eocene tropical ocean may have been as warm as 35C, as compared to about 29C today. The upward revision of tropical temperatures is quite a good thing for the CO2 theory, since it removes a good part of the “low gradient” problem, wherein models were thought to systematically exaggerate the pole to equator temperature gradient.

So far, so good. But then, just last year through heroic efforts involving a nuclear icebreaker, a conventional icebreaker and an icebreaking drill-ship. a deep-time sediment core was recovered from the Arctic ocean. The results, which came out in a series of papers in Nature (here,here and here) were startling. At times the Arctic was practically a freshwater lake, indicating some quite dramatic changes in the hydrological cycle. And more germane to the matter at hand, in the early Eocene, the Arctic was much warmer than previously thought. According to Sluijs et al ocean temperatures were as high as 23C — rather like Key West today. These temperatures come to you courtesy of a novel biochemical proxy known as Tex86, derived from certain lipids produced by tiny plankton called Crenarchaeota. Tex86 is the new wunderkind of paleoceanography.

Will wonders never cease? Evidently not. Just when the hothouse starts looking really, really hot, along comes a new Science article by Bornemann et al, dealing with climatic conditions in the Turonian (93.5 to 89.3 million years ago). The principal result of this paper is that there appears to have been a 200,000 year period right smack in the middle of one of the warmest periods of the past half billion years, when there were ice sheets (presumably in Antarctica) that were up to 60% the volume of today’s Antarctic ice sheets. How in the world do you get such large ice sheets in a high CO2 climate warm enough for crocodiles to survive in the Arctic at the other side of the planet? And this apparent glaciation is not the result of a global cold snap. As in the Eocene results quoted earlier, the tropical ocean surface temperatures are again on the order of 35C — courtesy once more of the wondrous Tex86 proxy.

How was the ice volume inferred? Primarily by an especially meticulous application of an old technique. When a glacier forms on land, the water it is made of is enriched in the lighter form of oxygen, 16O, which leaves the ocean enriched in the heavy form, 18O. Single-celled shelly creatures called foraminifera (“forams” for short) record this composition, but they are very subject to diagenesis. The key to the new estimate was to take samples from pristine glassy portions of exceptionally well-preserved foram shells. The sample was taken from a core in the Tropical Western Atlantic, so the investigators are able to determine tropical surface temperatures, making use of Tex86 proxies from organisms living near the surface. The ocean water isotopic composition is estimated using both surface-dwelling and deep-dwelling forams.

Since the oxygen isotope composition of forams depends on temperature as well as ocean water composition, the Tex86 proxy was used to correct for the temperature effect in forams living near the surface. There is no independent temperature proxy for the deep ocean, but the investigators assumed (a bit questionably) that deep ocean temperature did not change much over the time period. Be that as it may, the deep ocean oxygen isotope shift (uncorrected for any temperature effect) was similar in magnitude to the estimate from surface forams. Once you have the oxygen isotopic composition of sea water, you can translate that into ice volume by making an estimate of the isotopic composition of glacier ice. All this is easier said than done, but they did it. The glacial interval corresponds to the excursion of delta-18O toward positive values in the figure below, taken from the paper:

There is a useful commentary by Richard Kerr One must exercise the usual caution we urge in connection with radical results, and await confirmation before taking it to the bank. As Kerr points out, there is other data from this time period that doesn’t show the isotope shift.

There are two additional things I myself noticed, which seem inconsistent. The first is that in order to get reasonable numbers for ice volume, the investigators needed to assume that Antarctic ice in the Cretaceous period had the same isotopic lightness as Antarctic ice today. Most theories of fractionation would have Antarctic ice being less fractionated in a warm climate, however. Perhaps the high Equator to Antarctic gradient helps keep the Antarctic ice light, but this is something that needs to be checked. What’s even more troubling to me is that the bottom-dwelling forams (uncorrected for temperature) indicate the same ocean water isotopic shift as the temperature-corrected surface dwelling forams. However, if Antarctica glaciates, the deep ocean should be filled with cold Antarctic bottom water, which should produce an additional positive isotopic shift in the uncorrected bottom dwelling forams. That this shift isn’t seen suggests that something is amiss to me.

Still, this paper already has a lot of modelers scratching their heads. To give an example of the magnitude of the problem, I reproduce below a figure from one of Rob DeConto’s old simulations (Nature 421, (2003) ), showing the glacier distribution in Antarctica as a function of CO2, as CO2 is steadily decreased. These are done for orbital parameters favorable to Antarctic glaciation; the simulations don’t use Late Cretaceous geography, but they do give a good idea of how hard it is to get a big glacier in Antarctica with anything much above twice the preindustrial CO2.

It is salutary to keep in mind that in many past cases where data conflicted with robust modeling results, it turned out to be the models that were right and the data that was wrong. This was the case for the early satellite reconstructions of twentieth century lower tropospheric temperature, which showed a spurious cooling. It was also the case for early reconstructions of tropical climate during the Last Glacial Maximum, which failed to show the cooling we now know to prevail in that region during glacial times.

So, what does all this mean for CO2 and anthropogenic global warming? Does it mean we don’t know beans about climate, so let’s have a party and why worry? No, actually. All this hothouse strangeness gives us a great deal more to worry about. The tropics is not strongly thermostatted, and there appear to be feedbacks in the system that can amplify polar warming more than previously thought possible. Perhaps due to clouds? Matt Huber, one of the foremost Eocene modellers, stated in a recent seminar at the University of Chicago that he could get closest to reproducing the Eocene hothouse by assuming that the Earth’s real climate sensitivity is at the high end of the IPCC range — around 4C per doubling of CO2. Or, perhaps there are mode switches in the climate system we know nothing about, which we are risking triggering by increasing CO2. Without understanding the Hothouse climates, it’s impossible to say how close we are to the danger zone.

But what of this new riddle of Cretaceous ice? An optimist might say that the result shows that you can keep a lot of ice in Antarctica even in a very warm climate. On the other hand, the conditions allowing the ice to exist in a warm climate are evidently very fragile, since it was there (assuming the result holds up) for only 200,000 years — the wink of an eye, in geological terms. That could mean that the factors governing whether Antarctic ice stays or goes in a warm climate are more subtle than we thought, offering more possibilities for surprise transitions. Or it may turn out that Cretaceous CO2 is really only twice the pre-industrial level, but that there’s some whopping positive feedback which bumps up tropical temperatures to 35C. In a scenario like that, the strange and unexplained resistance of Antarctica to warming might save some Antarctic ice, but that would be cold comfort, since the rest of the world would be toast.

Or, it may turn out that the processes determining the glaciation and deglaciation of a partly ice covered Antarctica have nothing to tell us about the present situation starting with a large Antarctic ice sheet. I’d be surprised if this turned out to be the case, but it could happen. One thing is for sure — if the result survives, it will provide an important and challenging test for the next generation of ice sheet models.

Could it be that the glaciation is telling us that we are completely barking up the wrong tree with the CO2 theory of hothouse climates? Perhaps, but somebody will have to pony up a quantifiable alternative before that avenue can be pursued. And whatever the alternative is, the challenge of simultaneously explaining the coexistence of a super-hot tropics with Antarctic glaciation — and also explaining why this happened for only 200,000 years — is apt to be as big as any challenge posed to the CO2 theory. One could probably get a climate something like the suggested one by combining moderately elevated CO2 with making a lot of low clouds over Antarctica while making the rest of the world essentially cloud free (or somehow making the high cloud greenhouse effect dominant in the rest of the world), but that’s quite a stretch. If somebody comes up with a way of doing that which can be expressed in a sound mathematical formulation, I’ll be the first to want to have a look at it. Cosmic ray enthusiasts could have a field day with this, but I doubt they’d have much success.

However you slice it, it starts to look like the Eocene and Cretaceous are tugging at our sleeve, whispering to us “There are things going on with climate you don’t begin to understand. Proceed with caution.”

We already knew hothouse climates were interesting, but darned if they don’t just keep getting more and more interesting. It puts me somewhat in mind of the old Yiddish curse– “May you live in interesting times.” But, to paraphrase Maurice Sendak — Let the Wild Rumpus Continue!


308 Responses to “The debate is just beginning — on the Cretaceous!”

  1. 101

    Your very first comment points to tracking CO2 levels. Now pegged at either 382ppm or 394ppm depending on the source. But most disturbing is that NOAA data says rate of CO2 rise as about 2 ppm per year for the last few years.
    Increases per year NOAA data from ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_gr_mlo.txt

    2000 1.73
    2001 1.63
    2002 2.55
    2003 2.31
    2004 1.57
    2005 2.54
    2006 1.72
    2007 2.12

    This tracks out that we will reach 450ppm (a tipping point) by the year 2030. That is with typical yearly increases. Is this simple arithmetic correct?

  2. 102
    pat n says:

    re: 83

    Scientists have already put a public face and debated the “handful of credentialed sceptics like Lindzen …”. For example, in 2002 Ben Santer (LLNL) and Dennis Hartmann (U.W. Seatte) had a debate with Richard Lindzen on global warming at the University of Minnesota. I attended the debate with a co-worker and my NWS NCRFC Hydrologist in Charge (HIC) supervisor. It was overwhelmingly obvious that Lindzen’s points were not substantiated. However, my co-worker and the HIC said they were unconvinced that the topic of global warming warranted any hydrologic study or concern. Their story was already determined by their higher-ups at NWS and NOAA.

    http://picasaweb.google.com/npatnew/RoadBlockOnClimateChangeUnderstandingByNWSNationalWeatherService

  3. 103
    Chuck Booth says:

    Re # 13 Johnno: “…I think researchers should concentrate on stark problems like what if there are no viable fossil fuels left after 2040.”

    Do you mean all researchers in all fields of inquiry throughout the world? Or are you suggesting that climatologists whose expertise lies in, say, atmospheric physics, or ice core gas analysis, or physical oceanography and who may know little or nothing about developing alternatives to fossil fuels should switch fields? That would be asking a lot, don’t you think? Or, did you mean those researchers whose expertise in applied science and engineering would enable them to develop alternative fuels, and maybe also those political scientists, urban planners, psychologists, sociologists, etc, whose understanding of the issues could lead to solutions for dealing with the political and social consequences of switching to a non-fossil fuel-based economy?

    Re # 68 Dodo: “Crichton for one, has never made any claims to be an expert on the cretaceous. His specialty is the jurassic”

    The smiley face meant you were just being facetious, right?

  4. 104
    George says:

    I don’t understand the comments here (and elsewhere – it seems a recurrent theme) about the reluctance of scientists, especially climate scientists, to engage in public debate and discourse, not to mention how inept they are when they do try. Uhhh, isn’t that exactly what they’re doing here at RealClimate? Seems like public debate and discourse to me. The web is thick with scientific reports and papers, and the blogosphere appears to have no lack of scientists willing and eager to talk about them. And talk about them to anybody. Usually in an encouraging, respectful way. Even willing to patiently and politely respond, often in great detail and not infrequently more than once, to people whose questions suggest they are as thick as two planks. My science consists of forty-year-ago freshman university physics, but I can and have learned a lot from RealClimate and other science sites over the past year or so. I may not be able to understand the physics or follow the math, but I have no trouble with the written word, and the accounts and explanations and criticisms are always lucid and frequently thought-provoking if often rather depressing. Anyone who thinks that the future public debate and public discourse around climate change will happen in any significant way other than online is living in the past. Fortunately, scientists seem to be rather good at communicating via the web.

  5. 105
    Mark A. York says:

    “Deforestation accounts for roughly 20% of global greenhouse-gas emissions, so the U.S. is enhancing its efforts to conserve and expand the world’s forests.” JAMES L. CONNAUGHTON and DANIEL M. PRICE

    Is this true? Sounds high to me. My discussion in Nemo’s Locker has been through several full sceptic bingo cards but it boils down to distrust of models. It’s strange, engineering types have trouble with this and they empty the fallacy files trying to prove it. Pity really.

    “The problem is the people doing these adjustments. I don’t trust a single one of them to honestly and objectively follow where the data leads and to correctly identify root causes.”

    There is no way to correct for this level of personal bias.

  6. 106
    mg says:

    re 101. it is not obvious that it would do that, at least in terms of anthropogenic driving elements. one would need to look at the underlying world gdp and its response in order to ascertain the co2 concentration. the structural transformation of the global economy that is beginning, with its attendant shakeout phases across global supply chains, may temporarily give some degree of respite.

  7. 107
    Michael says:

    Having a healthy dose of skepticism is the only responsible approach to life. While accepting a body of knowledge is a valid approach, not accepting it and saying “we don’t know a thing at this point” is just as valid.

    Why the insecurity? If a percentage of the population thinks the IPCC reports are junk, why is that so threatening?

  8. 108
    Christina West says:

    41 pat n.

    thats awful. i read Hansen’s couple of articles on scientists being intimidated, but it comes home more to me when its first hand like reading the letters on your photo page. what did you observe that they didnt like?

  9. 109
    Philippe Chantreau says:

    George, it would be nice indeed if there could be some public place debate in which climate scientists could explain the basics and more. The problem with such a debate, as Tamino and others have pointed, is that it will have results that depends almost exclusively on subjective factors, such as how likeable (or even just good looking) the participants are, how funny, etc…

    The quality of their insights, information, knowledge, is essentialy irrelevant in a debate like that, although, these factors should be the most important. Science can not be fed to the public through TV and other mass-media, especially when the public is barely able to understand very basic (and that’s not an understatement) maths. If “debates” of that sort start happening on a regular basis, you can bet that the denialists will hire any kind of players (actors, whatever) likely to sway opinion, regardless of qualifications, and it will work. Manipulating minds is not difficult, whether in the US or anywhere else. A mind manipulating contest with the denialist camp not only verses in its (despicable) methods, but also gives legitimacy to an “opposing point of view” without any true scientific underpinnings. It’s a loose/loose proposition.

  10. 110
    Nick Gotts says:

    Re #107 (Michael) “While accepting a body of knowledge is a valid approach, not accepting it and saying “we don’t know a thing at this point” is just as valid.”
    Which of these is valid in a particular context depends on whether it is true in that context that “we don’t know a thing at this point”. Both cannot possibly be valid at once.
    “Why the insecurity? If a percentage of the population thinks the IPCC reports are junk, why is that so threatening?”
    Because there is an urgent need for action to avoid likely climatic disaster, and such ignorant or foolish people will be used by those obstructing such action because of vested interests.

  11. 111
    Thomas says:

    If I can change gears towards the public debate subject: RC does a good job, under a set of rules which gives the scientists an upper hand (i.e. the moderators can reject comments). In the more public political arena it is a lot easier to win with propaganda and false arguments. A cleverly stated false argument may convince a plurality of the audience even if it is competently refuted. I think we need another class of volunteer between the scientists and the public. I know scientists are working overtime just to maintain currency with their fields, and to add a bit of original research to boot. Few have the time energy inclination oe charisma to succesfully take on the public debate task.
    As this debate task requires a different skill set than scientific research it is only natural that specialization should occur. The debater has to have a very strong laymans understanding of the science, and hopefully can call upon the experts when needed. I suspect that many commenters, and lurkers come to RC because they see themselves as having some part in these debates, and want to better arm themselves with knowledge. This sounds like a good model to me.

  12. 112
    Dodo says:

    Re #101. Richard, thanks for the numbers on CO2 increments. Now, compare that to the global mean temperature increments over the same period. (May I recommend HadCRUT3, although GISTEMP seems to be the temperature of choice aroung here.)

    Any correlation? If not, and if the divergence persists, why should we worry about a 450 ppm CO2 value an sich? I thought it was the temperature we were afraid of.

    [Response: What is it about the phrase '8 years is too noisy to discuss trends' that people find so hard to understand? See the last post ad nauseum for why your question is ill-posed. -gavin]

  13. 113
    Hank Roberts says:

    Reminder to self:

    http://initforthegold.blogspot.com/2007/03/why-truth-is-losing-ground.html

    ——-excerpt——

    It all ties together into a pretty clever strategy:

    1. say things that are exasperatingly ignorant
    2. get real experts with little understanding of polemics to express their exasperation
    3. cast that exasperation as arrogance and bullying

    Nothing you can say will cause that person to change their opinion, because what they are voicing is not actually an opinion about a matter of fact but rather a tactic in a battle for influence over the casually interested…..

    —–end_excerpt——

    Just reminding myself to reread that whole thread more often.

  14. 114
    David B. Benson says:

    Dodo (112) — Go to the sidebar. Go down to the section entitled Science Links. The first entry is a link to the Discovery of Global Warming web site. Over there, read at least the section on Carbon dioxide as a greenhouse gas.

    Once you understand it, you too will worry…

  15. 115
    Andrew says:

    Re: 111
    I agree. Does anyone know if there is an umbrella organization that collates and communicates the latest AGW research for groups of professional societies? A sort of “Global Warming Research Center” thingy. There are many science-based professional organizations that communicate AGW concerns to their members and could use a hand sifting through the latest research. Here is an example from the Wildlife Society. I know the Society of Wetland Scientists is involved in communicating AGW research to their members but could find nothing on their web page. http://joomla.wildlife.org/index.php?option=com_content&task=view&id=175

    Accurate, up to date information in their hands would go a long way towards keeping the public informed on the state of AGW research and would help nip the latest conspiracy theories in the bud.

  16. 116
    Dodo says:

    #112, Gavin. Ad nauseam cuts both ways: You seem to be in denial of the simple fact that according to Hadley and the satellite measurements, no significant warmng has taken place since 2001, and even GISTEMP shows that warming has slowed down.

    I know that six years it is not a climatologically sufficient time period. I am just curious to know what you guys will do if this “global no warming” persist over the next solar cycle, or just two IPCC review periods.

    Over at Tamino’s blog I have committed myself to his challenge: if warming returns by 2015, I will admit that AGW is the most likely cause for most of the warming.

    Tamino has also promised to admit he was wrong, if it cools. Alas, we both think the debate will continue nonetheless. Maybe we should come together and make something bigger out of Tamino’s challenge? It would help to divide both camps into those that are willing to correct their beliefs by data from the real world and those who prefer dogma. I think RealClimate should be in the first group.

    #114. You didn’t get my point. CO2 is not toxic or harmful at these concentrations. Whether it is 450 or even 4500 ppm is a non-problem compared to the predicted consequences from temperature and sea level rises, whatever weights their many causes might have.

  17. 117
    Martin Vermeer says:

    Re #113 Hank:

    yes, it sounds rather hopeless, doesn’t it. However, I do think there is hope. The people the science should convince are not the population at large, those that wouldn’t know their dry adiabatic lapse rate from their hinterworks. They don’t need to be convinced… they’ll do, and believe, what the loudest, most persuasive sound bites in the public ‘discourse’ will tell them to do and believe.

    No, it is the people controlling between themselves the resources that would offset the Exxon et al. contribution.

    Think of the millions of American small — or not so small — entrepreneurs. These people have children — and grandchildren. And they must be reasonably smart, and have a functioning relationship with factual reality, to be successful entrepreneurs in the first place. And many of them are decent people too. We’ve got Soros already :-)

    They could be motivated to contribute. The work then, should be done by professionals at persuasion. We need an army of algores, well informed, persuasive, and — unusual for the job description — unconditionally honest. And they need the resources, including the best propaganda specia-lists money can buy, to work with and reach a broad audience; like the denialists.

    Cynical? Certainly. But that’s how politics with campaign financing and all works: a politician without a moneyed constituency in addition to a voting one, goes nowhere. Until that changes — if ever — you have to play the game by the existing rules.

    [Response: I would like to think that it is still possible to reach people with a scientifically sound message -- though I certainly agree that communication skills and making the nature of the problem vivid to the audience is essential. I think Gore did this pretty well, though one can quibble about certain aspects of the way he presented the argument, and the messenger himself causes about a third or a half of the intended audience to just tune out. One thing that might help would be to look at how the nation was brought round to addressing major problems in the past, particularly in cases which involved science. The Manhattan Project is one model -- a small technically elite core with access to the power structure makes a decision (I'm not arguing whether it's right or wrong) without consulting or being able to consult the public in general. The Clean Air Act and Clean Water act is another, though in that case the act was addressing harms that were already severe, not severe harms forecast for the future. --raypierre]

  18. 118
    Deech56 says:

    RE #113 Hank Roberts: Thanks for the link to Michael Tobis’s thoughts.

  19. 119
    Gautam Kalghatgi says:

    Re Gavin’s response to 112, the “problem” surely is that the the kind of changes that are being advocated to mitigate GCM, based on model predictions, are so drastic. It is not surprising that more confidence in the accuracy of GCM model predictions is sought before life-style changes of the scale that are required will be undertaken. This debate is happening with a background where world energy demand is going up inexorably, driven by increasing population, urbanisation, increasing wealth in the third world….. Moreover, future world energy consumption is going to be more carbon intensive as alternatives to oil (coal,oil sands,heavy oil) will come into greater play. Some projections suggest that the use of renewable energy, as a fraction of total world energy consumption, is actually going to decrease in the coming years e.g. as more and more poor people in the third world turn to gas and electricity for their energy needs. It is very difficult to see how any concerted, world-wide action can be taken sufficiently quickly to slow CO2 increases in the coming decades. This might, of course, mean the end of the world as we know it! On the other hand the GCM model predictions which are trying to model such a complex, highly multi-variate, higly non-linear system might not be quite right in their long-term predictions. As Gavin has pointed out before, the “uncertainty” in both the models and the measurements makes it difficult to “test” (or “falsify”) the models at the moment. It is not surprising that when some data start showing that the model predictions (e.g. as used in the IPCC reports) about future temperature rises might be too high, this attracts attention. Inevitably, in this debate “science policy” issues will be as, if not more, important than the science itself.

    [Response: You don't need GCMs to be concerned (see this previous post) - all they do is try and quantify it a little better. I have never said that you can't test the models - these tests are ongoing continuously. The issue I've had with some recent statements is that the tests are not very good, not that they shouldn't be done. - gavin]

  20. 120
    pat n says:

    Re #108 (Christina West),

    On what I you observed that they (NOAA NWS NCRFC) didnt like:

    As a National Weather Service North Central River Forecast Center snow and ice hydrologist from 1980-2000, I had responsibility for preparing the annual Spring Snowmelt Flood Outlooks for the Upper Midwest for the 1980s and 1990s.

    In January of 2000 I prepared a table on Red River streamflow above Fargo, ND which showed earlier in the year snowmelt runoff was already occurring in the basin, a trend which I thought indicated climate change due to global warming.

    I prepared to display my table the first annual Government Expo at the Mall of America in 2000. NWS supervisors ordered me not to do that and told me I was not to go to the Mall of America that weekend not even as a private citizen or I would risk disciplinary action.

  21. 121

    We finally got cable TV and I watched “Forecast Earth” last night. It’s great it’s there!

    Only one thing sounded slightly off to me. Heidi Cullen, when talking about reducing our CO2, said “which scientists believe is causing global warming.”

    I felt it should have been, “which scientist say is causing global warming.”

    It sort of sounded like we live in the scientific relativistic world where we have to respect each other’s scientific BELIEFS.

    Or, I do think scientists go thru a skeptical process in which the over- or underwhelming evidence leads them to believe or continue disbelieving some causal relationship. But once they believe that, then when they tell the public or write the text book they state it as a fact, at least as a fact with caveats, at least as a fact until some other scientist comes and disproves it.

    We the public just want the condenced version. We want what scientists say in simple, brief language. Just the facts. Many of us have lived long enough to understand the scientific progression of “facts,” that some facts today may be debunked or modified tomorrow. I don’t hold it against scientists who do the best honest job in finding then telling us the facts, which then may be assailed with better, more thorough science later.

    So perhaps it is correct for scientists at this point of sufficient evidence for GW to decline “debates,” by saying the issue has been settled, there are no debates at the general level of whether or not it is happening…..though I’d be interested to see any new peer-reviewed studies you have that point in a different direction, and I’d be happy to give you my expert assessment of it.

    Let’s face it most scholars only have time to read the abstracts and perhaps the conclusions (where the caveats might be) of peer-reviewed studies (unless it’s in their specific area), certainly not the reams of (dis)information coming from non-scientifc sources. And attending pointless “debates” is even more time-consuming.

    I think it’s enough that RC exists to constantly address the disinformation, untruths, and unfounded claims. Whenever I get in an argument about GW, I just tell them go to RC (of course, the ideologues are not going to do so). There is absolutely no way you can talk to these people or debate them. They sort of remind me of a relative I have… Or it’s like the advice I give some young married women I know …. there’s no use arguing with him when he’s drunk. Wait til morning.

    [Response: In describing the science as "settled" one must be careful not to give the impression that every conceivable thing having to do with human influence on climate is settled. Though I've used the word myself, there's a good case to be made that it should be avoided, precisely because it is so prone to confusion. There are some things that are indeed so certain that further argument has no bearing on policy options. That would include the basic operation of the greenhouse effect, the fact that the CO2 rise is almost entirely due to fossil fuel burning and deforestation, and I'd argue for pushing the line all the way to the water vapor feedback. Other things are still very much in a state of flux -- notably the impacts of global warming, for example on extinction and tropical diseases. These things are unlikely to be satisfactorily nailed down in time to affect the policy actions that need to be sorted out in the near future, so here the question is more a matter of what you consider a credible risk, and how to weigh in uncertain risks that could indeed be catastrophic. That's what politics is for. That and value judgements, as in how to weigh, for example, polar bear survival vs. the money to be made by easier Arctic oil exploration. -raypierre]

  22. 122
    Jim Galasyn says:

    And now a word from our corporate masters:

    Big business says addressing climate change ‘rates very low on agenda’
    Poll of 500 major firms reveals that only one in 10 regard global warming as a priority
    By Tricia Holly Davis, Geoffrey Lean and Susie Mesure
    Sunday, 27 January 2008

    Global warming ranks far down the concerns of the world’s biggest companies, despite world leaders’ hopes that they will pioneer solutions to the impending climate crisis, a startling survey will reveal this week.

    Nearly nine in 10 of them do not rate it as a priority, says the study, which canvassed more than 500 big businesses in Britain, the US, Germany, Japan, India and China. Nearly twice as many see climate change as imposing costs on their business as those who believe it presents an opportunity to make money. And the report’s publishers believe that big business will concentrate even less on climate change as the world economy deteriorates.

    The survey demolishes George Bush’s insistence that global warming is best addressed through voluntary measures undertaken by business – and does so at the most embarrassing juncture for the embattled President. For this week he is convening a meeting of the world’s largest economies to try to persuade them to agree with him.

    The meeting – in Hawaii on Wednesday and Thursday – follows the US’s refusal to accept binding targets for reducing carbon dioxide emissions, the main cause of global warming, in international negotiations in Bali last month, and is seen as an attempt to develop a less rigorous approach to the crisis.

    But the new report shows that even business does not support this, with four out of the five companies surveyed wanting governments to take a central role in tackling climate change.

    The survey, carried out by the consulting firm Accenture, found that only 5 per cent of the companies questioned – and not one in China – regarded global warming as their top priority. And only 11 per cent put it in second or third place. …

  23. 123
    Ray Ladbury says:

    Hank, While I think Michael Tobis’s thought have much to recommend them, it is a mistake to view the business establishment as monolithic in their aversion to climate science. To paraphrase George Washington–people act in accord with their interest. The key is to make sure they perceive those interests clearly. It is mainly the extractive industries (coal, oil, power, etc.) who feel threatened by the need to take action on climate change. Insurance is starting to realize that climate change means uncertain risk, and that is very bad for their business. GE sees significant potential advantages from supplying “green” technologies.
    Likewise different nations have different perceptions. The US, with the largest proportion of energy/capital intensive industry feels the most threatened, and oil-rich states like Russia, etc. feel the most threatened by mitigation, while for island states, threats due to rising sea level are already a reality.
    We will never get people, corporations and nations to act against their interests, but perhaps we can get them to see their interests more clearly.

    Where we fall into the trap of the denialists is in debating the science in a nonscientific forum with nonscientist judges. Rather, we need to stress that the science is not at all controversial. The proper range for debate is what to do about the threats that science has alerted us to.

  24. 124

    The Bornemann paper is fascinating. I reviewed it for Science and agree with most of what you say. But you seem to lack perspective on the development of this idea. The Bornemann paper provides data supporting the Matthews-Stoll-Miller hypothesis. Matthews was scorned. Stoll and Schrag were ignored. And we (Miller et al., 1999, 2003, 2005a, b) finally convinced the community to look.

    The hypothesis is that large (>25 m), rapid sea-level change can only be explained by changes in continental ice sheets. Exxon Production Research company (EPR) first identified large, rapid sea-level changes in the Mesozoic (Vail et al., 1977; Haq et al., 1987; Hardenbol et al., 1998). These changes were controversial, in part because of problems in methodology and proprietary data (Christie-Blick et al., 1990; Mial et al., 1991). We have worked on the New Jersey margin to independently develop a global sea-level (eustatic) estimate for the last 100 myr (Miller et al., 2005a, Science; go to http://geology.rutgers.edu/miller.shtml for reprints). We show that the timing of the EPR sea-level falls is largely correct but their amplitudes were too high by a factor of 2-3. For example, the mid Oligocene fall was not 400 m (Vail et al.,, 1977) or even 160 m (Haq et al., 1987) but 55 m (i.e., about the same ice in Antartica as today). Ours is not the final answer because it is largely derived from one margin, though it is supported by comparisons with other margins. But to paraphrase Winnie, ours is the worst of sea-level curves except for the others that have been tried.

    Our records strongly suggest moderate sized ice sheets (8-12 mkm3) occurred in Antarctica during the Late Cretaceous greenhouse and caused 25-40 m eustatic lowerings. We provided provisional links to oxygen isotopic increases that would be expected for such a relationship. Bornemann slam dunked this with their data.

    How to reconcile ice sheets the greenhouse? We have a paper in Marine Geology (2005b) that suggest that the ice sheets were ephemeral (we suggested 100 kyr in a quasi 3 myr period; Bornenmann’s data suggest 200 kyr glacial). These ice sheets did not reach the coast and ocean temperatures near Antartica were still quite warm (see maps in Miller et al., 2005b).

    Now as to the relationship with CO2, this is still speculative. Proxy data suggest CO2 could have been 2x of 10 x. Which is it? I would speculate, both. Most of the Late Cretaceous WAS an ice-free greenhouse with very high CO2 (greater than 4x). But there were a dozen or so “cold snaps” (as Dana Royer dubbed our glaciation) in the Late Cretaceous when ice sheets developed.

    Remember in discussing Late Cretaceous to Eocene climates, we are talking about over 50 myr of time. The world was not uniform through this greenhouse period.

    I see no contradiction in the relationship between CO2 and climate from looking at the greenhouse world of the Late Cretaceous to Eocene.

    Ken Miller
    Professor II and Chair of Earth and Planetary Sciences
    kgm@rci.rutgers.edu

    [Response: Ken -- thanks so much for posting this additional information, and thanks also for your patience in dealing with the quirks of the way the comment box treats the less-than symbol. I hope your comment will help redirect some of the discussion back onto the nature of the hothouse climates. I did indeed want to debate the nature of debates, but not to the exclusion of the interesting scientific issues raised by this problem. --raypierre]

  25. 125
    Hank Roberts says:

    Ray, I’m sure MT isn’t suggesting what you think. He’s pointing out how the repeated faux-stupid faux-naive questions are used to try to cause real scientists to get short tempered in public. Different.

    The BP Chief Scientist’s video I pointed to elsewhere is an excellent example of a corporation starting to be very serious about climate change. (The tactic attacking _them_ is faux-environmentalists piling into threads saying BP isn’t perfect so must be an enemy.)

    Just noting, many endlessly repeated native questions are tactical.
    A few are real, new, naive or young questioners. Patience furthers.
    Detecting which are tactical requires Google for repetitions.

  26. 126
    Steve Reynolds says:

    raypierre> That and value judgements, as in how to weigh, for example, polar bear survival vs. the money to be made by easier Arctic oil exploration.

    How about tackling value judgments that are not so one-sided? Say: how to weigh, polar bear survival vs. maintaining the rapid emergence from poverty of billions of people in China and India.

  27. 127
    Hank Roberts says:

    > Bornemann slam dunked this with their data.

    Clarify please? Bornemann blocked this idea, or confirmed it?

  28. 128
    Bryan S says:

    Re #122: Ken, thank you so much for providing your important perspective on the issue of eustacy. In my comment #78, these are exactly some of the points I was alluding to (I have in fact recently posted several comments on Real Climate citing many of these same papers which you have listed). It seems that the proprietors of this websight have been only slightly amused and somewhat confused by my comments.

    Many of us in the geology community who work with a great deal of seismic data have long suspected that Matthews may have been at least partially correct, and that ice sheets may have been present (to a greater extent than most have suspected) even in very warm climates during the Cretaceous and early Cenozoic. How else do you drive rapid eustatic sea-level changes even in the Eocene? Tectonic processes are too slow, and many events are certainly global in scope. Many geologists have found the EPR eustatic sea level curves to be largely correct, but may lack scale concerning the absolute magnitude of various highstands and lowstands (just as you have stated). An excellent paper for those wishing to review the correlation between the d18O proxy and the Haq. et al (1987, Mitchum et al., 1994) curves is Abreu and Anderson (1998). Personally, I am coming to suspect that both the proxy record and sequence strat record are telling us something important about deep time climate: Global climate change does not necessarily equal regional change (should be no real surprise), and the regional changes over the Antarctic have controlled ice sheet mass balance and thus eustatic sea level changes. I am worried however, that so many interested people are so biased against any scientific research that Exxon has developed, that they may reject it without even examining its merrits. For all interested in such a study, be aware that an examination of only the d18O proxy record is incomplete without a simultaneous examination of sea level curves.

  29. 129
    Joanne Ballard says:

    Dear Raypierre,

    As scientists, we know that science is never settled.

    Why would you not debate i.e. Fred Singer, Tim Ball, John Christy, Roy Spencer, Bob Foster and other skeptics? Scientists are skeptical by nature. Aren’t you?

    I am sure that many people would learn from such a publicized interchange of ideas. Why not? It could be a great fundraiser for further climate research.

    Joanne :-)

  30. 130
    per says:

    Re 113, Why discussing with climate change skeptics may be harmful.

    If one wish to debate with hard core CO2 greenhouse skeptics, it is important to remember that predicting their next move involve considering if they could possible doubt something you might have used consider as obviously true. That combined with the endless task of separating false beliefs from cleverly presented facts designed to cause allergic reactions among enviromentalists, and to make things even worse, knowledgable profesionals for some reason acting like they where ideological gullible CO2 skeptics, MAY cause a lethargic dumbed down state of mind.

    Guessing the latitude and mechanism of cretaceous deepwater formation does not do that, rather the opposite :-)

  31. 131
    pat n says:

    It has been said that the Chicxulub asteroid hit (65 mya) drastically reduced solar radiation and affected global climate. How long?

    Could other asteroids have led to Cretaceous ice sheets and drops in sea level during the Paleocene?

    http://www.palmod.uni-bremen.de/FB5/geochron/Robert/RPSabstr.html

  32. 132

    #124: ” Most of the Late Cretaceous WAS an ice-free greenhouse with very high CO2 (greater than 4x)”
    Everywhere on earth? No whitecaps on high mountains?

    From what I gather the late Cretaceous Antarctica was not centered at the South Pole. Which makes it highly likely a naturally much warmer place.

  33. 133
    Hank Roberts says:

    > any scientific research that Exxon has developed, that they may
    > reject it without even examining its merrits.

    Ken, just as a reader, when I see scientists funded by Exxon publish their work, I’m delighted. People at Exxon show up in the citations, perhaps more than those from other companies. It’s good to see.

    It’s no secret many very good scientists are doing models — e.g. where the continents and sedimentary basins were in geological time.

    I know there are commercial reasons to keep some work secret. But that’s not like what’s surfaced in pharma, where only “successful” trials got published and doctors got misleading effectiveness data.

    If models didn’t work to find oil, y’all wouldn’t be paid to make them — right?

  34. 134
    Rich Creager says:

    I, and perhaps others, wouldn’t mind a bit more information about Tex86, on which the science part of this post is largely based. Thanks.

  35. 135
    David B. Benson says:

    Dodo (116) — Then either you did not read it or you did not understand. The consequences of increased carbon dioxide in the atmosphere take some time to work out. The approximately 500 billion tonnes of carbon added to the active carbon cycle has already increased the temperature enough to affect precipitation patterms: droughts in the Sahel, East Africa, the Mediterranean shores, Australia, the southern portion of the Amazon basin and in the southeast United States; severe flooding in South Asia and south China; other disruptions to agricultural production in eastern Europe. Already the world grows short of food. For example, the price of white wheat obtained by local farmers is more than triple the price one year ago.

    Does not appear to be ‘normal variablity’ to me, based on the known increases in CO2 concentrations, which are certainly of human origin.

  36. 136
    Chris Colose says:

    # 130

    Given that there is so much uncertainty in this discussion, it is not plausible for you to expect anyone to know if there was ice on particular mountains or not.

    This is a good site for looking at paleogeography
    http://jan.ucc.nau.edu/~rcb7/globaltext2.html

    Antarctica would have been the only likely place to have significant ice at the time. The troposphere probably would have been much too hot at lower latitudes, but we don’t have a clue as to Antarctic paleoelevation

  37. 137
    Hank Roberts says:

    >Tex86

    Google is productive of much information by using that as the sole search term. Scholar would likely do even better. Picking one from the first page of regular Google results (follow the cites for more)

    http://www.geo.arizona.edu/web/HumanEvolutionWorkshop/pdf/Johnson.T.pdf.

    —excerpt_follows—–

    … TEX86 (TetraEther indeX of tetraethers with 86 carbon atoms), is an index developed by (Schouten et al., 2002) for determining sea surface temperature from marine sediments. The index is based on the composition of tetraether membrane lipids produced by the aquatic microbe, Crenarchaeota. We have found this group of compounds to be preserved in the sediments of many large lakes, and we have determined that the TEX86 index established by Schouten et al. (2002) for SST’s in the marine realm holds up remarkably well when compared to mean annual temperature of the lake surface waters (Powers et al., 2004)and subsequent analytical results).
    Application of the TEX86 index to a piston core from Lake Malawi, East Africa, provides a fascinating and credible history of lake surface temperature spanning the past 24,000 years (Powers et al., 2005)…..

  38. 138
    Rod B says:

    Hank (113), I understand your point, but the object of climate scientists entering into such public discourse is not (should not be…) to dissuade the opposing “discoursee” but, like him, sway the audience.

  39. 139

    #136 Chris, From the paleo reconstruction maps I’ve seen, the South Pole had ocean at or very near by during the Cretaceous. Making all kinds of climate scenarios possible, especially with Australia
    joined with Antarctica, there must have been some strange polar dinosaurs during that era.

  40. 140
    Rod B says:

    Jim (122), I’m not sure what you were expecting, but to cite ole Cal (I think), “the business of business is business.” At least that’s the way business sees it (mostly — they’re not completely monolithic). The most astounding stat to me in your post is that 5% of giant 500 companies have global warming as their #1 priority! Unless they’re in only a business that is exploiting GW (making biofuel, hydrogen-based engines, wind turbines, etc.), they are clearly not watching the store and will shortly be in the bottom 500. Of course they are aware of the potential problem, but it isn’t their yob; that’s why they want the goberment to work on it; then they can go on producing widgets which is what they get paid to do.

  41. 141
    Chris Dudley says:

    Raypierre,

    Your response to #14 intrigued me. Currently the Antarctic is quite dry and there is little hope for much heat transfer to it from condensation because the water vapor supply is depleted before it reaches the interior. On the other hand, the Arctic gets more precipitation because ocean currents carry heat north and there is evaporation from the warm water. If the heat transfer to the poles can be carried out via condensation of vapor carried in the atmosphere then there would be less energy available to ocean currents and one would not want to think of the poles (or North Pole) as a fresh water lake, but rather as a fresh water lens that occurs owing to a preferred mode of heat transfer made possible by the greater vapor carrying capacity of a warmer atmosphere. Fresh water might also form a lens around the land at the South Pole as well. The induced salinity gradiant, pole to equator could be weakened by ocean currents arising from other factors which would remix the waters, but the possibility of a preference for heat transfer through the atmosphere rather than the oceans when more vapor is available in the atmosphere with higher temeratures seems interesting to me. Is this something models can investigate or are the ocean currents to difficult to manage yet?

  42. 142
    Chris Colose says:

    129 Joanne Ballard

    skepticism and deliberate misrepresentation of data are two different things. We’ll say that ‘they’ have given ‘skepticism’ a bad name.

  43. 143

    5 Stages of Climate Grief

    Public debates could charitably be public display of grief. The first stage is denial.

    Recommend a recent lecture on global warming – by Nobel scientist professor Steven Running at the University of Montana. This is a video lecture with graphics. He does a pretty good job of covering the fundamental science (it seems to me) – it does last an hour, but is not at all complex. Very compelling – I have been forwarding it widely.
    http://www.forestry.umt.edu/personnel/faculty/swr/Presentation/SupportingFiles/ViewerWM64Lite.html Although he uses maps of the Northwest region, there maybe similar data sets for other regions.

    Professor Running closes with just a brief discussion of the emotions that will meet anyone following this topic. It is like grieving any loss. He calls it the 5 Stages of Climate Grief. (After Kubler-Ross ) http://www.ntsg.umt.edu/files/5StagesClimateGrief.htm
    Denial, Anger, Bargaining, Depression and Acceptance.

    Perhaps if we see these as natural states of human processing we can move out of the denial and anger states that seem to trap us. Bargaining seems everything from government to personal. Right now it is all I can do not to get depressed. And acceptance does not mean inaction.

    One goal is to observe without anxiety, and then act without fear.

  44. 144

    raypierre:

    … Gore … and the messenger himself causes about a third or a half of the intended audience to just tune out

    I don’t think that’s entirely fair. If you analyze this, you realize that it is just anti-intellectualism, plain and simple. People hate Gore because he speaks like an intellectual — and adding insult to injury, is right most of the time. Many folks of little formal training have a big problem with that.

    Putting scientists on this job would be just as bad an idea. They are just not equipped for it, while tobacco lawyers, e.g., are. I would guess that it would be easier to house-train a tobacco lawyer for truthfulness then to turn a scientist into a successful persuader.

    Note that truthfulness is not a prerequisite for successful persuasion. It’s just that the truth has practical advantages. Like, there is only one of it, whereas untruths come in a broad variety; so you don’t have to keep track of which untruths you told yesterday, or which ones your organization is committed to :-) And, you can use the same base material for “defense in depth”, refuting popular denialist talking points popularly, scientifically, or somewhere in between, depending on what your audience will bear.

    We’ll have to see how Gore’s The Climate Project works out. The idea is right.

  45. 145

    Re #136 Chris Colose:

    but we don’t have a clue as to Antarctic paleoelevation

    An important point. Would this be relevant?

    http://www.sciencedaily.com/releases/2007/07/070720095954.htm

    I don’t find the article itself.

  46. 146

    Dodo posts:

    [[You seem to be in denial of the simple fact that according to Hadley and the satellite measurements, no significant warmng has taken place since 2001, and even GISTEMP shows that warming has slowed down.]]

    And you seem to be in denial of the fact that from February 2007 to August 2007 the temperature rose significantly.

    Same sort of argument. Fallacy of composition. The part doesn’t necessarily reflect the whole. You have to use all the data, not just a little bit of it that seems to support your argument.

  47. 147

    Steve Reynolds posts:

    [[How about tackling value judgments that are not so one-sided? Say: how to weigh, polar bear survival vs. maintaining the rapid emergence from poverty of billions of people in China and India.]]

    Despite the constant refrain to the contrary from denialists, it is possible to deal with global warming and still have billions emerge from poverty in China and India. The dilemna, reduce poverty or mitigate global warming, is a false one — a fallacy of bifurcation.

  48. 148
    Stuart says:

    Re: the Exxon/Haq et al relative sea level cycles

    At this point, the proxy isotope evidence for these putative Cretaceous glaciers is quite equivocal. As has been noted, Moriya et al (Geol. 35(7), 2007), provide equally strong data that such glaciation did not exist.

    But even if the Bornemann ‘event’ is confirmed over time, it is hard for me to see how it will provide a plausible explanation for the Exxon/Haq et al Cretaceous (and other warm period) **relative** sea level cycles. Relative sea level is the **horizontal** component of sea level change: the basinward or landward movement of sea level associated with “transgressions” and “regressions.” This is the raw data observed from seismic sequence stratigraphy.

    On average, these cycles clearly have a much longer cycle time usually quoted in the 1-3 Myr range (for the Cretaceous I estimate 1.75 Myrs). They are characterized by a relatively slow million-year ‘onlap’/transgression followed by a relatively abrupt ‘offlap’/regression. If interpreted as a glacier then this implies a slowly melting glacier over a Myr time period followed by a rapidly growing one (i.e. just the opposite of the behavior of the Late Pleistocene ice sheets.)

    By comparison the Bornemann event looks well confined to 200 Kyr with short-lived growth and melting. Surely this 200 Kyr event can’t be the model for Myr coastal onlap stratigraphy.

    I’ve argued (Gaffin, JGR v96(B4), 1991 p6701; Gaffin, J. Geol., v100, 1992, p. 717), that what we may be dealing with with the Haq et al cycles is something quite different, but just as important as the question of Cretaceous glaciers: internally generated sedimentary cycles that may require little or no eustatic (i.e. vertical) sea level forcing.

    It’s interesting to me that people seem to have a hard time with this idea whereas its long been the approach Pleistocene ice sheet modelers have taken (starting with Weertman, 1976 and followed by others too numerous to list) to reconcile the weak vertical forcing of the snowline by Milankovitch cycles, with the large 100 Kyr ice sheet response. Indeed many similarities exist between these two outstanding paleoclimate cycle problems (Gaffin, 2008, submitted to Clim. Change.)

  49. 149
    Ray Ladbury says:

    Steve Reynolds, have you been to China or India? Yes, a small elite are emerging from poverty, but at an environmental cost that is utterly unsustainable. And in India, the veneer of wealth is even thinner. Moreover, to state that the only way poverty can be fought is by destroying the environment is an absolute fallacy.

  50. 150
    Appy Sluijs says:

    Hi Ray,

    [Response to 73.: Thanks for stopping by, Appy. Hope to meet you sometime. Indeed the PETM deserves a post of it’s own. Are you guys going back to drill the Arctic again anytime soon or do the Russians have their icebreakers tied up with their territorial claims on the Lomonosov ridge? –raypierre]

    Territorial claims may actually be a more of a problem than the sea ice for drilling the Lomonosov Ridge again. We can probably use the JOIDES Resolution in a couple years! Proposals to drill some more Arctic core are already in the IODP system.

    Hope to meet soon!

    Appy


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