Pliocene #1: North Greenland

In most "long" presentations of climate change in the IPCC framework, we see Vostok ice core going back to about 800 Kyr, covering most of the Pleistocene. What easily gets lost sight of in this format is just how unusual the Pleistocene itself is. It is one of only a few glaciations in the entire history of the earth. There have been some interesting recent discoveries in the Pliocene – the geological period just before the Pleistocene. Here is some information on an interesting Pliocene wood sample collected in 1997 from north Greenland (c. 80°31.9″‚ⱎ, 65°25″‚ⱗ, 70 m).

Here is a picture of the Pliocene wood sample:
North Greenland

Ole Bennike reported here:

it is obvious that the trees grew locally, since leaves, needles, seeds and cones are common, and the rich fossil insect fauna also comprises numerous species that are dependent on trees (BàƒÆ’à‚ⵣher 1995)….Of the tree trunks from the Kap KàƒÆ’à‚ⷢenhavn Formation, only a few measured more than 10 cm in diameter, and the largest sample had a diameter of 18 cm. The lack of pines in the Kap KàƒÆ’à‚ⷢenhavn Formation distinguishes that flora from most Late Cenozoic floras from northern Canada.

He compared the site to northern Canadian sites as follows:

From the Worth Point Formation on Banks Island trunks of Larix up to 26 cm in diameter have been reported. Laric laricina is the only conifer reported from the Worth Point Formation; this sequence is considered to be around 1.5 Ma old (Matthews & Ovenden 1990). The floristic composition and the size of the wood fragments from Washington Land bear strongest resemblance to that of the Beaufort Formation on Meighen Island and the high-level alluvium on Ellesmere Island, for which a Mid or Late Pliocene age is suggested, perhaps around 3 Ma.

These larix stumps appear to be comparable in size to those at the Polar Urals site (where the cutoff for modern sampling was about 10 cm). North Greenland in the Pliocene was tectonically almost exactly where it is now, but Arctic climate was not simply warmer than today, but a lot warmer. The Miocene was even warmer. On this scale, Milankowitch factors would not be anything other than a modulating factor. The placement of the start of the cooling into the Pleistocene is about 1.4-1.5 Ma.

I’ve noticed some other interesting Pliocene references, which I’ll post up from time to time.

Ole Bennike Late Cenozoic wood from Washington Land, North Greenland. Downlaoded from


  1. Paul Gosling
    Posted Apr 5, 2005 at 2:56 AM | Permalink

    And your point is?

  2. Steve McIntyre
    Posted Apr 5, 2005 at 6:12 AM | Permalink

    Just before the Pleistocene, the Arctic was much warmer than at present. Milankowitch orbital variations don’t explain this: so what was the cause? I don’t know the answer, but it seems like a pretty relevant question.

    Also because I’ve been looking closely at larix ring width information at the Polar Urals site, it is interesting to see information on Pliocene larix ring widths in far north Greenland.

  3. Michael Ballantine
    Posted Apr 5, 2005 at 6:40 AM | Permalink

    And the point is, that our climate has been a LOT warmer and a LOT colder and man had nothing to do with it. It just is. There is plenty of evidence for this without resorting to highly questionable mathematical flummery to interpret “signs” in growth patterns that have little more insite than the reading of chicken bones.
    Our efforts should be to better understand our climate and to improve our adaptability to the changes. Arguing about spending billions of $ on limiting a minor green house gas makes as much sense and 2 fleas arguing about how to guide the path of a dog by tugging on a couple hairs on it’s back.

  4. Timme Donders
    Posted Apr 5, 2005 at 9:50 AM | Permalink

    … however, we need to go back roughly 34 million years ago before exeeding those “minor greenhouse gas” changes we’re seeing now. Surely earth’s climate has changed, extremely so as a matter of fact, but this does not mean that de-stabilizing it at this speed without uderstanding the consequences is a very good idea. Of course life on earth will not suddenly stop in it tracks because of man changing climate, as you point out the earth has seen bigger changes. But not before has there been a human society in existence that largely depends on natural reserves/agriculture/fishery etc, think of the impact a climate shift has on food production and general economic conditions. The problem is we don’t know for sure .. but just imagine the costs if it is … that far outweighs investing now while there is still a window of opportunity to change things.

  5. Spence_UK
    Posted Apr 5, 2005 at 12:50 PM | Permalink

    … however, we need to go back roughly 34 million years ago before exeeding those “minor greenhouse gas” changes we’re seeing now.

    As I’ve pointed out before on this site, there are other proxy data for the CO2 concentrations other than the IPCCs favoured ice core records, such as the leaf stomata records of Wagner et al that show the CO2 concentration was at just a shade under 350ppmv just 8,600 years ago (i.e. well within the era of modern man), suggesting that recent CO2 levels may not be as unprecedented as many think.

    In addition, this is CO2 only, which is a second order greenhouse gas behind water vapour, a tiny change in water vapour in the atmosphere would have a much larger effect than a CO2 variation.

    but just imagine the costs if it is … that far outweighs investing now

    This is a challenging cost/benefit analysis that is far more qualitative than quantitative, and so is probably more a matter of opinion – my opinion happens to fall on the other side of yours. I believe the money would be better spent ensuring we are able to cope with (or minimise the effects of) natural disasters rather than trying to prevent them, because the likelihood of successful prevention is minute (e.g. even if the AGW scare were true, efforts like the Kyoto protocol would have minimal impact).

  6. Michael Ballantine
    Posted Apr 5, 2005 at 1:01 PM | Permalink

    Timme, why go back 34 million years? The last ice age was only 10,000 years ago. The “hockey stick” team contends that the last hundred years have seen dramatic warming compared to the last 2000 years. There is a lot of data that says the last hundred years is NOT unusual or the warmest in the last 2000 years.
    I do agree that our cultures have become very dependent on a very narrow climate window. Most of the humans who have ever lived are alive today and have lived in reasonably stable climate all their lives. The earth is a dangerous place and most people have either forgotten it or never lived it first hand. We, as a race, have become complacent in our survival skills. Witness the Christmas tsunami. A wake up call to all the people living complacently on the edge of an ocean and treating it like a benign pond.
    Whether or not man’s contribution in GHGs is having a significant affect on the climate or not is almost irrelevant. If we do not get better at adapting to the natural changes, which can be HUGE, it won’t matter. We will go the way of all the other creatures of the past who could not adapt to their changing environment. The only thing that really sets us apart from all the extinct creatures is that we have been pretty good at adapting, so far.

  7. Larry Huldén
    Posted Apr 5, 2005 at 11:47 PM | Permalink

    According to James Hansen (founder of modern anthropogenic warming) the main difference between “believers” (Hansen) and “sceptics” (Lindzen) is basically opinions of what happens if CO2 would be completely removed from the atmosphere:
    1. Hansen: Green house effect will completely crash = 33 centigrade decrease of mean temps of the world. Water vapor would not have any effect without existence of CO2.
    2. Lindzen: Only marginal effect. Water vapor would still have a profound influence on the green house effect.

    So, we have now the following problem: We know that CO2 levels have been increasing 400-1000 years after an increase of temperatures in the past. During the recent 100-150 years or so the increase in CO2 level is produced by man. We also know that the incoming warming radiation is now stronger than the outgoing radiation. Is that difference specifically caused by CO2 (including Methan etc.) or is there room for unknown factors in the whole balance?

    If we follow some recent alarmists’ claims of 10+ centigrades increase in the near future, the green house effect would be nearly linearly dependent on the level of CO2. I highly doubt that the majority of climate scientists really thinks so.

    Lindzen’s theory of an iris effect of water vapor is obviously not correct. However, Hansen and Lindzen may still be both close to the truth. It is unlikely that CO2 level ever would drop to zero. As a consequence CO2 will all the time maintain the influence of the water vapor on green house effect.
    The basic unknown parameters are still the RELATIVE INFLUENCE of the VARIATION in CO2 levels and the VARIATIONS in the WATER VAPOR. The variations in the past CO2 levels are still controversial and the latter can still not be modelled.

    I think that tree ring studies, lake sediments and ice cores are in a key position in our understanding of equilibriums in the climate system.
    The models are definitely not independent of the knowledge of the past.

    It is quite clear that models are getting unreliable by basic errors in the statistics of climate reconstructions of the past.

  8. Paul Gosling
    Posted Apr 6, 2005 at 1:34 AM | Permalink


    Pointing out that the climate of the earth was much warmer millions of years in the past without human influence, as if this is some sort of revelation, and thereby implying that this throws doubt on the potential influence of human activity on the climate system is the worst sort simplistic argument. I would have expected better from you.

  9. Timme Donders
    Posted Apr 6, 2005 at 1:39 AM | Permalink

    I happen to actually work with Wagner who published about relatively high CO2 levels around the “8.2 event”, the recent view on the issue is that ice cores underestimate the “high-variability signal” in the CO2 record, simply because closing-in gas bubbles takes 50-100 years and thus naturally smoothes the record. But the absolute values have an offset (so the stomata vs. the ice cores) that has as yet not been explained, it means that either the stomata or the ice cores are off (and most likely a bit of both). However, it is funny to see how much the ice-core community ignores the stomata work as it doens’t agree totally with their results. but it’s by no means an argument to wave away the present CO2 rise

    I mentioned 34 million years ago as that is the most likely date at which the “modern-day” values were reached, (say, around 300 ppm, see Pagani et al, 2002, paleoceanography) as opposed to 1000-2000 ppmv before that period. But even without very absolute data on the precise amount of CO2 in the air, it’s hard to think of any geological process which would bring so much carbon in the atmosphere in such as short time as in the last 100 years. ( if you ignore massive vulcanism for the moment, which would have many very nasty consequences in any case such as acidification and actual cooling by blocking sunlight).
    But this is a totally different discussion, the point I really wanted to make is that all the critism on flawed reconstructions of climate over the last millennia is good as it sharpens the debate and lets (hopefully!) the main players in this issue look at their data and methods again. But it’s too easy to simply brush aside concerns about global warming, since even with instrumental data a warming has been observed which can’t be explained simply by looking at the natural forcings involved. Whether unprecedented or not, it’s clear that things are changing and the soure of the change as we see it now, namely CO2, not only has an impact on greenhouse conditions but also on acidification of oceanwaters. Combined they are pretty unique in earth’s history and therefore need more attention. I understand it’s very complicated matter and therefore it’s good that people like McIntyre from outside the traditional climatology look at this issue to point out flaws and errors in studies, but it doesn’t mean that there is some big “conspiracy” going on and therefore going into the debate as GHW “sceptics” against “believers” is a pretty useless attitude, which doesn’t bring us much further.

  10. Spence_UK
    Posted Apr 6, 2005 at 2:18 AM | Permalink

    Water vapor would not have any effect without existence of CO2.


    I’m confused by this statement above. Do you mean “water vapour would not have any effect without the existence of CO2” which is a peculiar claim to make or do you mean “without CO2 the levels of water vapour in the atmosphere would collapse” which is more plausible but incredibly difficult to demonstrate! Do you have references for where Hansen makes this argument?

    It is unlikely that CO2 level ever would drop to zero

    This I am glad about – if CO2 levels dropped to zero, then the temperature would be the least of our worries, as pretty much all life on earth is dependent on the presence of carbon dioxide in the atmosphere.

  11. John Davis
    Posted Apr 6, 2005 at 5:02 AM | Permalink

    I have a problem with the whole “water vapour feedback” idea. As I understand it, the theory is that increased warming (from CO2) causes more water vapour in the atmosphere which increases the warming still further. Now this is a system with positive feedback, and the simplest characteristic of such systems is that they just keep on going up (or down!)until some kind of limiting condition is reached. So you’d expect the temperature to just keep on ramping up…more water vapour…more heat…more water vapour, more or less irrespective of the CO2 content.
    My guess is that this is exactly what does happen, but that it happens in the transition from ice-age to current conditions (& vice-versa). Right now we are in the upper temperature stable state, although stable needn’t mean rock-solid constant.
    At a further guess, I’d say that the limiting mechanism is probably cloud formation. More water, more clouds seems fairly likely; so my prediction for future climate is slightly warmer, especially at night, and slightly duller.

  12. Steve McIntyre
    Posted Apr 6, 2005 at 7:36 AM | Permalink

    Paul, right now I don’t know how big the human impact is on climate. I’m not saying that it’s negligible, I’m merely saying that some of the “proofs” of 20th century uniqueness are invalid. I’m really quite puzzled at the lack of specialist consensus on the causes of big changes. My own presumption is that the tectonic closing of the Panama isthmus around 2.6 Ma had a major impact on ocean currents and led to a big change from the Pliocene to the Pleistocene, but some of the timings seem odd. The Worth Point Formation in Banks Island is dated 1.4-1.5 Ma and is still warm.

    I’m also mentioning the Pliocene rather than the Cretaceous or Jurassic or some relatively remote period, because the Pliocene is the period just before the standard Vostok 800 Kyr graphic. It’s not remote in geological terms. There was an Antarctic ice cap in the Pliocene though.

  13. Larry Huldén
    Posted Apr 6, 2005 at 8:15 AM | Permalink

    # 10. I don’t know exactly how the mechanism is expected to work if CO2 could be removed, but at least James Hansen and some others are of that opinion. Hansens statement is found on:

  14. Dave Dardinger
    Posted Apr 6, 2005 at 9:04 AM | Permalink

    Re #11:

    Right on, John! Cloud formation must serve as a negative feedback mechanism, and most all negative feedbacks operate in proportion to the amount of movement away from equilibrium. Thus while we can calculate how much the earth’s temperature would have to increase to balance radiatively the forcing from additional CO2, the additional clouds formed will reduce the amount of that forcing and increasingly so as it increases. The equilibrium will probably be a degree or two higher than present, but mostly where it does no harm, as you say in winter or at night.

    Further, we can’t really use the prehistoric concentration of CO2 to tell us much about how far from equilibrium we are since plants drag the CO2 value down as far as they can and still survive. We also know there’s constant replenishment of CO2 from ocean circulation and erosion and the respriation by animals, which serves as a check on the amount of plants present. So it’s likely that plants have a lot of capability to handle more CO2, in the long run, and this means that if we give them a little hand via planting, fertilization, etc., any warming which occurs will quickly come to a halt. Indeed, maybe things like more hunting, to reduce the pressure on plant growth in the short run, would be beneficial to the earth’s ecosystem in the long run. (Just tweaking the greenies, don’t jump on me).

  15. Spence_UK
    Posted Apr 6, 2005 at 9:43 AM | Permalink

    Re: #9, thanks for the reply, which was interesting and insightful.

    I appreciate that the current levels of CO2 are higher than even the leaf stomata records show for recent history, and that the link between fossil fuel burning and CO2 concentrations are too close to be ignored – I would concur that the current CO2 levels are almost certainly inflated from fossil fuel burning, but to show a flat line followed by a +25% hike tells a very different story to a waving line followed by perhaps a +10% hike above the upper bound.

    But this ties in importantly with climate models. Most of these include a strong positive feedback in the CO2 concentration, which can be justified from the low variability in the past (from the ice core records). If CO2 was more variable in the past, such a strong feedback is difficult to justify.

    This fits in with my own understanding of chaotic systems. A strong positive feedback may exist temporarily but the complexity of the system can switch this suddenly into a negative feedback, the decision on when this happens can be in the 15th significant figure of a seemingly unrelated parameter. In fact I believe that this is almost certainly the case otherwise the climate system of the earth would be inherently unstable.

    So my belief is that the underlying complexities of the climate system (which are chaotic by nature) includes checks and balances that can swing feedbacks, the very feedbacks that the runaway global warming theory needs to persist for hundred of years to produce the alarming results.

    All of this is, of course, impossible to prove either way. My personal opinion (and it can be no more than that) is, on the balance of evidence, that the climate system is inherently more stable than we give it credit for (albeit stable through chaotic mechanisms).

    but it doesn’t mean that there is some big “conspiracy” going on and therefore going into the debate as GHW “sceptics” against “believers” is a pretty useless attitude, which doesn’t bring us much further.

    This is a more tricky question to address! I agree wholeheartedly that people working together would achieve more than the arguments that often occur in this field. But unfortunately it is a very highly charged topic, which polarises people, who then take very strong and political views – on both sides of the fence. I don’t think there is a conspiracy as such, but I do believe that a percentage on both sides of the debate take things a little too far – an unfortunate consequence of human nature. Another aspect of human nature is that we are quick to overlook mistakes made by those with a similar viewpoint to our own. This doesn’t make a conspiracy, but it adds to the polarisation.

    Your views are interesting though, and offered without the prejudice that often comes with climate change discussions. Now that would be a good precedent to set!

  16. Spence_UK
    Posted Apr 6, 2005 at 10:07 AM | Permalink

    Re #13, thanks for the link.

    I see Hansen’s claim is from the feedback effects (my emphasis); his statement is that removing CO2, along with other trace gases, with water vapour allowed to respond would remove most of the natural greenhouse effect.

    This implies that removal of all CO2 would cause a positive cooling feedback that would (essentially) freeze the earth. As ever, it makes a good argument but is, in reality, completely impossible to prove without over-simplification of a chaotic system.

  17. John G. Bell
    Posted Apr 6, 2005 at 1:32 PM | Permalink

    Re #14 on hunting. Having run into a deer on the highway, and being a practical man, I hope your idea inspires others. Wouldn’t it be easier to deplete the worlds fish stocks? Wait we’ve already done that, and to think it might just save us from an environmental disaster. As far as “tweaking the greenies”, some talk about Pacific Ocean phytoplankton being limited by iron. I’ll try to throw some railroad spikes into the Pacific next time I’m out that away if I can get them on an airplane. Oh rats, I’ll have to fly in a human powered plane so the extra weight might be a problem. Well I’ll just have to try not to breathe too hard on my way out and hope for the best.

  18. John Davis
    Posted Apr 7, 2005 at 6:08 AM | Permalink

    Just by coincidence, RealClimate have today posted a piece on water vapour:

  19. Spence_UK
    Posted Apr 7, 2005 at 10:35 AM | Permalink

    John, (re #18)

    Thanks for the link, that more or less confirms my views above. Water vapour dominates the greenhouse effect, and the projections are dependent on feedbacks between water and temperature to cause the alarmist predictions.

    This still runs into the basic problems that I listed above. These highly positive feedbacks create a fundamentally unstable system. This would be fine if CO2 was tightly controlled (as indicated by the Vostok ice core records), i.e. if CO2 was controlled by something other than climate. But in practice I suspect CO2 concentrations are quite variable naturally, but then if you believe the positive feedback thing, then the climate would drive itself out of control naturally.

    Given that climate does not drive itself out of control on a regular basis, I can only assume that this is due to the fact that the chaotic nature of the climate means that extrapolating such feedbacks is inappropriate (in a complex, chaotic, interacting system sense). The interactions are prone to switching unexpectedly, something which is well observed in chaotic systems. It still seems to me the most plausible explanation for the evidence at hand.

  20. Hans Erren
    Posted Apr 8, 2005 at 2:11 AM | Permalink

    re #19


    Even with a low climate sensitivity of 1K/2xCO2 (0.28 K/Wm-2), this still yields a projected temperature rise of 2.5 degrees for the A1FI scenario. So the problem lies within the Neo-Malthusian exponential growth in the economic emission scenarios.

  21. Ferdinand Engelbeen
    Posted Apr 14, 2005 at 3:55 PM | Permalink

    Re #9,


    It is pretty sure that mankind is responsible for the recent increase in CO2 in the atmosphere. That is not a point of much discussion. The point is what effect that has on temperatures.

    From history we know that in pre-industrial times CO2, as far as is measurable, always lags (ocean) temperature changes. That is even visible in stomata data (as far as I remember, Rike Wagner pointed to a lag of CO2 stomata data at the end of the 8.2 kyr event or the Younger Dryas – but I don’t remember the source that good). The lag of CO2 levels after temperature changes is especially visible at the end of interglacials. While there is a lag of only 600 +/- 400 years at the onset of an interglacial period (which makes a feedback from CO2 possible), the lag is several thousands of years when temperatures decrease toward a new ice age.
    At the end of the previous interglacial, CO2 levels start to decrease at the moment that the temperature nearly reached it’s minimum and had no measurable effect on temperature (for a 50 ppmv level change)… Although the temperature record is disputed for it’s amplitude (due to differences in interpretation of the deuterium changes vs. temperature changes), that doesn’t change the timing of the decreases. CO2 lags, while CH4 doesn’t lag, thus excluding timing problems between ice age and gas age or bubble closing time length changes… See the discussion at: (#187795 gives the timing of the data from the Vostok ice core).

    Even in industrial times, CO2 changes due to ENSO-induced sea surface temperatures are superimposed over the increase due to fossil fuel burning. CO2 levels increase faster some 6 months after the start of an El Niño and slow down with the opposite.

    In much longer time records (as far as reliable), there is not much correlation between temperature and CO2. There were times with low CO2 (as today) and high temperatures, as good as high CO2 and low temperatures. What seems true is that there is a maximum global temperature of around 20 C, no matter external influences (solar or other). See:

    I have read the Ph.D. work of your (ex?) roommate Tom van Hoof on CO2/stomata for the period 1000-1500. While I did find almost all of it very interesting, I do disagree on the “modelled” influence of CO2 on temperatures, because of the foregoing.

    About CO2 levels in air and ocean water, that is far from unique, as one compares that with e.g. the Cretaceous, where CO2 levels were 3 to 10 times (depending of the source…) higher than today. Of course, CO2 levels in ocean water were much higher than today too, thus more acidic. Despite that, the same species of plankton living now, was highly productive in warmer waters and formed the white cliffs of Dover amongst a lot of other deposits… Of course, we only can hope that the genes coping with the lower pH still are intact…

    While it is prudent to reduce our use of fossil fuels for reasons of dependency of not so stable countries and to reduce pollution, CO2 levels or global warming seems not to be the most urgent reasons to do so…

%d bloggers like this: