According to a recent paper** published in the journal Nature, only a dramatic fall in atmospheric carbon dioxide levels are able to explain the transition from the mostly ice-free Greenland of three million years ago, to the ice-covered Greenland of today.
I am not convinced, but anyway, the paper begs the question, why did the purported elevated atmospheric carbon dioxide concentrations fall to levels similar to the pre-industrial era?
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** Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels, Nature 454, 1102-1105 (28 August 2008), by Daniel J. Lunt, Gavin L. Foster, Alan M. Haywood and & Emma J. Stone.
Read the University of Bristol media release here.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Good question Jennifer, but has it not also occurred much more recently than 3m yrs ago? and if it could happen at least twice before without any puny contribution from AGW, what is to say it is not happening now under the natural cycles?. There appears to be a lot of unknowns identified in this paper, so I’m not too excited by it either.
Published in Nature, well whaddaya know?
If the only tool you have is a hammer, every problem looks like a nail.
Exactly the kind of career enhancing, grant monkey product of the burgeoning science worker industry G Bird was talking about a few threads back.
Read the article, am not really competent to comment on the technicalities, but if you have a model, that is biased to the CO2 effect, what other outcome would you expect?
Reminds me of doing the same thing over and over and expecting a different outcome.
This paper seems to confirm Arrhenius’ hypothesis of ice age genesis but it doesn’t – it’s based on computer modelling in which the CO2 – temp relationship is an inbuit assumption – that increasing CO2 causes warming and reducing CO2 causes cooling – and thus their conclusion is an example of circular reasoning.
So the drop in CO2 can’t be the cause the of Greenland Ice Sheet formation but may well be related.
And the linkage between litho-debris on the sea floor surrounding Greenland is a bit problematical as well – it’s the well known ice raft theory that has more to with armchair induction than field observations.
It’s based on the belief that glaciers detach rocks and then hold them in suspension as a base load, as some icy-bluetack analog. While an innovative idea, there is little direct observational evidence that this actually happens.
So the appearance of litho-debris around Greenland (and how that is dated is another issue) as a result of ice sheet dynamics remains speculative. It’s a similar problem to the presence of large erratics on the Russian Steppes, and other northern latitude land masses – ice transport is the preferred mode of deposition but as the size of the erratics diminishes longituidinally, fluvial deposition has to be considered. However that demands fluvial, or water, transport of tsunami magnitudes over continental masses the size of Russia, and from the armchair perspective, this is too fancy. It implies the sloshing of oceans over the land masses – what possible force could do that?
So, if the world is starved of CO2 it becomes an iceblock?
Not a good scene if it’s true.
Which are we more in danger of? Too much CO2 or too little?
“Which are we more in danger of? Too much CO2 or too little?”
Wrong question. It’s a matter of what are we adapted to. That is the current level.
SJT
Webster’s Dictionary would be proud of you as the source of another example of the classic non-sequitur.
SJT
In fact the cartoonist Wiley might actually give you a commission for some of them for his “Non Sequitur” columns.
And isn’t it interesting how the SJT’s of this world manage to derail the comments here, not from malicious intent but from quite mundane ones.
Spangles,
What the Nature paper summary does not detail is the derivation of the CO2 levels pertinent to the study – that requires buying the paper I suspect.
As preliminary analysis, per above, shows it to have some flaws in logic, I am not going to buy it.
Odd that in order to be scientific one has to buy a scientific paper – if it were proper science, the paper would be available in the public domain.
I do appreciate the costs associated with publishing scientific papers, but to quarantine ideas on the basis of whether one can afford it or not, is another matter.
Jennifer, this might be a worthy topic for a new thread.
Its all rubbish. What happened was simply that North and South America fused, increasing the oceanic resistance to circulation and thereby reducing the temperature of the planet. Of course lower CO2 would have been the upshot of all that.
I think Graeme Bird has pinged the answer. To be quite honest, I saw something like that being explained in an Earth science documentary I watched recently…
Perhaps Lunt, Foster, etc, should’ve watched it too…. Would’ve saved em some time and their Government some money.
The usual stupid array of comments from people who haven’t read it.
I agree that (from the press release info) this is another circular reasoning argument. They use models that can’t accurately predict current climate changes, but assume they can work 3 million years ago.
I presume that the paper explains how they modeled the ocean currents under slightly different continental configurations to show that they couldn’t do it and that they also, showed how CO2 didn’t drop because the ocean temperature dropped as a result of the many natural cycles, like orbits, sun variations, cosmic rays, etc.
I understand they need to make a headline that is catchy, but why as scientists do they have to be so absolute. Couch it to say that CO2 reductions may be a driver based on the models. Then they can say that more research is needed to fund them to study other climate cycles and to get the models fixed, if they can, before anything definitive can be concluded.
Spot on – so after eliminating the best alternative hypotheses through reasoned argument, they should have concluded that it wouldn’t be last one standing. So you’d immediately dismiss CO2 warming and flip a coin on a loopy alternative. Makes sense.
What we do know from core results is that parts of Greenland now covered by ice were once large forests only 400,000 years ago, so this proves—-
Luke: It sounds as though you have access to the article. From what I can tell from the supplementary info that’s available for free, they studied four separate hypotheses for the glaciation of Greenland. I can find no mention of an interactive study or of any interaction between ocean temperatures and CO2 levels. Did they assume the three non-CO2 hypotheses had no relationship with one another? Did they assume that the changes in the oceans had no interaction with atmospheric CO2? If you could answer those questions, Luke, I would appreciate it.
The big hypothetical question: how good was parameterization of the GCM if they can’t identify what drove CO2 levels down?
Give them time neville and the AGW fanatics will prove it was neanderthals driving around in SUVs that caused massive global warming which caused the world to reach the tipping point and were thus annihilated in the ensuing disaster. There has just got to be some correlation which scientifically proves this beyond any doubt, or should I say that it is “virtually certain” that this is what happened. ( Oh God I am getting as crazy as Luke)
Geophysical Research Abstracts, Vol. 8, 04929, 2006
SRef-ID: 1607-7962/gra/EGU06-A-04929
© European Geosciences Union 2006
The formation of the Panama Isthmus during the
Pliocene in a fully coupled GCM – implications for
northern hemisphere cooling.
D.J. Lunt (1,2), A. Haywood (2) and P.J. Valdes (1)
(1) University of Bristol, (2) British Antarctic Survey
It is thought that the final closure of the Panama seaway, and formation of the Panama
Isthus, occured during the Pliocene, approximately 3.0-4.0 MyrBP. It has been suggested
that this had a number of effects on the earth-system, including the intensification
of the North Atlantic MOC, leading to elevated Atlantic SSTs at high latitudes,
and an associated intensification of the hydrological cycle. It has been further suggested
that this increased supply of moisture at high latitudes led to the growth and
establishment of the Greenland ice-sheet, ultimately leading to the onset of the glacialinterglacial cycles of the Quaternary.
In this paper we first present results from a pair of GCM simulations of the Pliocene,
with and without the Panama Isthmus.We use the fully coupled dynamic atmosphereocean
model, HadCM3. The Pliocene boundary conditions, including orography and icesheet extent, are from the PRISM project. We then present results from the GLIMMER icesheet model, which we force using the GCM-predicted climatologies. The GCM results show the expected post-closure warming of the North Atlantic, in addition to a warming in the Greenland Sea and an associated cooling in the Barents Sea. The temperature over Greenland also increases post-closure, as does the precipitation,
in particular in the East. Putting the GCM results into the icesheet model indicates an increase in the size of the equilibrium Greenland icesheet after the formation of the Panama Isthmus, supporting the hypothesis that this event was very significant in determining the subsequent evolution of the Earth-System.
Final closure of Panama and the onset of northern
hemisphere glaciation
G. Bartoli a,*, M. Sarnthein a, M. Weinelt a, H. Erlenkeuser b,
D. Garbe-Scho¨nberg a, D.W. Lea c
aKiel University, Institute for Geosciences, Olshausenstr. 40, D-24118 Kiel, Germany
bLeibniz-Laboratory for Radiometric Dating and Stable Isotope Research, Kiel University,
Max-Eyth-Str. 11, D-24118 Kiel, Germany
cDepartment of Geological Sciences, University of California, Santa Barbara, CA 93106, USA
Received 26 November 2004; received in revised form 10 May 2005; accepted 10 June 2005
Available online 21 July 2005
Editor: E. Boyle
Earth and Planetary Science Letters 237 (2005) 33– 44
Abstract
The Greenland ice sheet is accepted as a key factor controlling the Quaternary bglacial scenariob. However, the origin and
mechanisms of major Arctic glaciation starting at 3.15 Ma and culminating at 2.74 Ma are still controversial. For this phase of
intense cooling Ravelo et al. [1] [A.C. Ravelo, D.H. Andreasen, M. Lyle, A.O. Lyle, M.W. Wara, Regional climate shifts caused
by gradual global cooling in the Pliocene epoch. Nature 429 (2004) 263–267.] proposed a complex gradual forcing mechanism.
In contrast, our new submillennial-scale paleoceanographic records from the Pliocene North Atlantic suggest a far more precise
timing and forcing for the initiation of northern hemisphere glaciation (NHG), since it was linked to a 2–3 8C surface water
warming during warm stages from 2.95 to 2.82 Ma. These records support previous models [G.H. Haug, R. Tiedemann, Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation, Nature 393 (1998) 673–676.[2]]
claiming that the final closure of the Panama Isthmus (3.0– ~2.5 Ma [J. Groeneveld S. Steph, R. Tiedemann, D. Nu¨rnberg, D.Garbe-Scho¨nberg, The final closure of the Central American Seaway, Geology, in prep. [3]]) induced an increased poleward salt and heat transport. Associated strengthening of North Atlantic Thermohaline Circulation and in turn, an intensified moisture
supply to northern high latitudes resulted in the build-up of NHG, finally culminating in the great, irreversible climate crash at
marine isotope stage G6 (2.74 Ma). In summary, there was a two-step threshold mechanism that marked the onset of NHG with glacial-to-interglacial cycles quasi-persistent until today.
This largely irreversible climate crash is also
reflected by a profound and rapid reorganization of the northern high-latitude faunal provinces. For example, Atlantic planktic foraminiferal high-latitude provinces shifted dramatically southward while low latitude provinces contracted [32]. In the Northwest Pacific, the proportion of Coccolithus pelagicus, today a typical cold-water phytoplankton species, jumped to 80% at 2.74 Ma [33]. This event is linked to the onset of NHG and precisely coeval with the separation of Pacific and Caribbean coccolithophorid assemblages, which results from the final closure of the Panama Isthmus [34]. The benthic foraminifer Cassidulina teretis which
is adapted to low nutrients, harsher over-all conditions, and perhaps to higher seasonality became dominant at Rockall Plateau (DSDP 552) along with the irst occurrence of IRD and cold-water planktic foraminifers [35]. Our new centennial-scale record of ODP 984 now defines the sudden dominance of C. teretis in the Upper NADW level and the rapid reorganization of the North Atlantic THC at precisely 2.74 Ma (Fig. 3f).
Hmmm,
The preceding must have been a short post ;-O
You know before the wrecking-ball act that is modern climate alarmism, the fact of why this all happened was well-known. Geologists simply talked about the formation of the Isthmus of Panama and the consequent effect on climate. Not only when the two oceans were finally cut off completely. But in the lead-up to it.
Now its ESOTERIC KNOWLEDGE when it used to be just blandly accepted as the obvious reason. And in the alternative idiots view of the scenario, how did this dissapearance of the CO2 come about? And why then? Why then and why not some other time?
I tell you we are dealing with morons and all must be sacked and off the public tit for all time.
You know before the wrecking-ball act that is modern climate alarmism, the fact of why this all happened was well-known. Geologists simply talked about the formation of the Isthmus of Panama and the consequent effect on climate. Not only when the two oceans were finally cut off completely. But in the lead-up to it.
Now its ESOTERIC KNOWLEDGE when it used to be just blandly accepted as the obvious reason. And in the alternative idiots view of the scenario, how did this dissapearance of the CO2 come about? And why then? Why then and why not some other time?
I tell you we are dealing with morons and all must be sacked and off the public tit for all time.
We have the theory. And we have ample paleo-evidence. Every time oceanic flows are more restricted we get cooling. Not just to that area where the heat transport is reduced BUT GLOBALLY.
And the theory of it is basically undeniable. That when we apply Stefan Boltzmanns law hyper-regionally. Then we see that the better the mixing the better the heat retention.
So why would we be in denial of such obvious theory and practice match-up.
Its the same with Heinrich events. If the ice breaks free in such a way as to free up the Gulf Stream we will see a rapid warming. Not just up there but everywhere. And its obvious that we would do.
Thats the difference between the alarmist armchair scenario and this one. THIS ONE PANS OUT IN THE DATA.
This ‘paper’ is up there with Ammann and Wahl and Sherwood and Allen and anything done by Hansen and Mann; historically, there is no correlation between CO2 and temperature;
http://www.junkscience.com/images/paleocarbon.gif
http://www.geocraft.com/WVFossils/last_400k_yrs.html
And therefore no correlation between CO2 levels and ice levels. The isolation of Antarctica 35 million years ago, along with interruptions to thermohaline circulation, is the key to subsequent climate cooling.
There was a “dramatic” drop in CO2 levels 3 million years ago – from 300 ppm to 280 ppm.
Nature papers are freely available for reading, and for copying at any university library for a couple of bucks.
The cost to have a paper sent to you, if you can’t get to a library yourself but a friend can, is even less.
This is next to nothing in a private enterprise world.
And if one disagrees with a paper in Nature, one is absolutely entitled to write a rebuttal and submit it for consideration. If one feels that Nature inappropriately rejects such a rebuttal, there is always recourse to publishing on the web and embarrassing the editoral board of the journal when your insight is made available to the world.
It doesn’t have to be difficult.
So, the paper saying that only changes in CO2 levels are able to explain the glaciation transition 3 million year ago in Greenland must show how the papers that Steve Short cites don’t cut it.
Yeah and they don’t do it. And so everything we thought we knew prior to this science fraud taking over simply has to be ethnically cleansed due to the stupid-talk express.