Guest Post by Willis Eschenbach
The quote above is from Lord of the Rings, an exchange between Gollum and Smeagol, and it encapsulates my latest results from looking into the Shakun 2012 paper, “Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation” (paywalled, at Nature hereinafter Shakun2012). I discussed the paper in my post “Dr. Munchausen Explains Science By Proxy“. Please see that post for the underlying concepts and citations.
When I left off in that post of mine, I had investigated each of the 80 proxies used in Shakun2012. I plotted them all, and I compared them to the CO2 record used in their paper. I showed there was no way that the proxies could support the title of the paper. Figure 1 recaps that result, showing the difficulty of establishing whether CO2 leads or lags the warming.
Figure 1. All proxies (green dots) from Shakun2012 (Excel spreadsheet). CO2 values digitized from Shakun 2012 Figure 1a. There is pretty good agreement between the warming and the changes in CO2.
Note that the proxies say the earth generally warmed from the last ice age, starting somewhere about 15,000 BC, and the warming lasted until about 9,000 BC. Since then, the proxies have the greatest agreement (darkest green). They say that the globe generally cooled over the length of the Holocene, the current interglacial period since the last ice age.
Today I was thinking about that single record that they used for the CO2 changes. I got to wondering what other ice core CO2 records might show about the change in CO2. So I went and downloaded every ice core CO2 record that I could find that covered the time period 26,000 BC to modern times. I found a number of ice core records that cover the period.
Then I collated all of them in Excel, saved them as a CSV file, opened the file in R, and plotted every ice core CO2 record that covered the record from 26,000 BC up to the present. I standardized them over the same period covered by the Shakun2012 CO2 data. There was excellent agreement between the Shakun2012 data and the ice core records I had downloaded … but there was also a surprise.
Figure 2 shows the surprise …
Figure 2. As in Figure 1. Black circles show Shakun2012 CO2. Additional colored dots show the ice core CO2 records which have data from 26,000 BC to the present.
Dang, I didn’t expect that rise in CO2 that started about 6,000 BC. I do love climate science, it always surprises me … but the big surprise was not what the ice core records showed. It was what the Shakun2012 authors didn’t show.
I’m sure you can see just what those bad-boy scientists have done. Look how they have cut the modern end of the ice core CO2 record short, right at the time when CO2 started to rise again …
I leave the readers to consider the fact that for most of the Holocene, eight centuries millennia or so, half a dozen different ice core records say that CO2 levels were rising pretty fast by geological standards … and despite that, the temperatures have been dropping over the last eight millennia …
And I leave everyone to ponder how far climate “science” has fallen, that a tricksy study of this nature can be published in Nature, and can get touted around the world as being strong support for the AGW hypothesis. The only thing this study supports is the need for better peer review, and at a more basic level, better science education.
My best to all, stay skeptical,
w.
Source data:
ICE CORE CO2 DATA: All ice core CO2 data are from the NOAA Paleoclimatology site, the “Ice Core Gateway” page, in the section “Gases”.
[UPDATE] A hat tip to Jostein, in the comments he points out that the original Shakun Nature paper is here (pdf).
barry says:
“If I close one eye and squint through the other, tilt my head a bit and skim, I just might be able to come away with the impression that the literature only ever mentions CO2 lagging temperature rises, and that CO2 changes have no impact during glacial transitions.”
Then you’re doing it wrong. And Willis has effectively deconstructed Shakun et al. in several incisive articles. To put it bluntly, Shakun’s paper is cherry-picked crap.
barry says:
April 11, 2012 at 6:57 pm
CO2 also lags temperature in the Greenland cores. So all this south-north stuff is hogwash.
What Shakun et al. are doing is the “Younger Dryas two step”. They take advantage of the fact that in the YD cold interval, temperatures fell but (interestingly) CO2 did not. They exploit the fact that there were two temperature rises, before and after the YD, but only one CO2 rise.
This is because the overall rise in temps from glacial to interglacial was ocean driven, thus it leaves a CO2 signature, while the YD was likely an atmosphere driven event due to volcanism or an impact of some sort. You will find that ocean driven temperature changes drive CO2 changes while atmosphere driven temperature change does not so much.
In the other transitions, interglacial to glacial, the lag of CO2 is much larger – too large for even Shakun to sweep under the carpet. Does CO2 amplification only work with increasing temperatures, not decreasing? Why did CO2 not fall during the YD? Why did CO2 rise in the latter half of the Holocene while temperatures fell?
This idea that CO2 first follows temperature rises caused by Milankovich orbital changes (although soon no doubt even Milankovich – not being in the cosy Anglosaxon family of the core AGW elite and with a scary east-european name – will be airbrushed out in favour of fire-lighting antics of protohumans and australopithecines, mammoth farting, etc..) is the most flagrant and absurd breach of Occam’s razor (and Occam is even nice and English!). CO2 follows then amplifies then leads? Pull the other one! If this were so then there would be an exponential form to temperature rises, which there is not.
Well, you could be right. I didn’t think the science was settled owing to problems with Greenland ice cores (as different to SH cores which are very clean), but perhaps your insight is keener or more up to date. Can you cite a couple of studies which settle this matter – in such a way that there is no longer any doubt? I’d genuinely like to learn of such.
But whatever the case, it’s beside the point I was making. Has anyone suggested that CO2 leads in any part of glacial transitions prior to Shakun et al? Yes, they have. There are other interpretations of glacial transitions that do not discuss a CO2 lead, or assign less weight to GHG feedbacks than most studies, but the point is that Shakun’s ideas are not new in any way (including the role of ocean circulation), and the surprise and outrage hinging on such a supposition are misinformed and misplaced. All you have to do is read the literature (for instance, the half dozen or so examples I cited above).
The main difference between Shakun and previous studies is that Shakun et al incorporate more data from a greater variety of locations. On the surface, that would seem like a good idea.
barry is beating a dead horse. The Shakun paper is crap. No one really bothered to review it because it said what they wanted to hear. It’s still cherry-picked crap; worthless as science and only good for alarmist propaganda.
Willis:
Congrats on an excellent deconstruction of a shaky (pun intended) and deceptive reconstruction! Something that caught my attention is the rise in CO2 in the early Holocene that you figured out and plotted in Figure 2 above. I’d noticed the same phenomenon in some other data I’d seen, and mentioned it in a book I wrote and self-published on global warming (Global Warming False Alarm) a few years ago. In the book, I pointed out that the continued rise of CO2 after the global temperature had leveled out after the last ice age is completely inconsistent with the AGW belief that today’s rising CO2 has caused global warming. Am now working on a 2nd edition of the book – would be glad to send you a copy when it’s finished.
Here is yet another paper that posits Southern warming and CO2 rise leading Northern warming.
Full abstract:
“Temperature differences between the hemispheres and climate temperature variability” – Toggweiler & Lea (2010)
The professors here may conclude that it’s all hogwash, but at the very least its clear the notion is not peculiar to Shakun, but has been discussed in the literature for more than a decade.
Barry:
Thanks for drawing my attention to that paper by Toggweiler and Lea. However, if you look very carefully at their Figure 1, which compares the CO2 level to both Antarctic and Greenland temperatures, you’ll find that CO2 not only lags temperature in the Antarctic, but also (just) in the Northern hemisphere. I agree that the conclusion about the seesaw effect between the two hemispheres is the same as Shakun’s, but the two papers are not saying the same thing about the CO2 lag.
This thread is about Willis having observed an apparent ‘hide the incline’ in the paper by Shakun.
A previous article on WUWT by Willis deconstructed the paper by Shakun; see
http://wattsupwiththat.com/2012/04/06/a-reply-shakun-et-al-dr-munchausen-explains-science-by-proxy/
Some here are conducting a debate in this thread on the analysis in the paper. But that debate is appropriately conducted in the previous thread: this thread is about the ‘hide the decline’.
And the ‘hide the decline’ is embarrassing to the AGW ‘cause’. It seems the embarrassment is so great that supporters of the cause don’t want to discuss it. Indeed, they even prefer to discuss Shakun’s junk science as a method to avoid discussing the subject of this thread.
Richard
Ralph,
not just the paper I have cited but a number of others have posited the same general conslcusion as Shakun et al, whose general description of glacial termination is that the Southern warming caused CO2 rise, which then spread the warming to the North. From the paper I’ve just quoted, we don’t need to eye-ball graphs and make guesses abouit pixels – we can read what the authors themselves say.
That is as clear as can be. We don’t need to reinterpret.
I am not arguing that this has definitely been the process during glacial terminations, just that Shakun et al do not overturn previous hypotheses. The excitement in the skeptical milieu comes from a shallow understanding of the science. It’s not that the paper has said anything new, it’s just said it more plainly, and thus more directly confronted a canard in the general debate.
Barry:
I’d seen that statement in the abstract of the paper you cited, but my interpretation of the paper is that the Northern response to CO2 (where CO2 led) was very slow – tens of thousands of years, much longer than the 600 years or so lag of CO2 in Antarctica. Shakun et al are saying that the CO2 lead at the end of the last ice age was only 460 yr globally, 720 yr in the Northern hemisphere.
It seems to me that the two papers are very different in this respect, although I have to agree that the underlying idea is similar. Even Skakun at al refer to Toggweiler and Lea’s conclusion as CO2 being “largely a consequence rather than cause of past climate change”. But of course they wanted to push their own paper, so that may not be an objective statement.
As I mentioned in an earlier post, I’m revising the book I wrote on global warming three years ago. The Shakun et al paper caught my attention as I’m currently working on a section titled “Two-faced CO2” in a chapter on climate sensitivity. As I’m not a climate scientist (though a PhD in Physics), I want to be extra sure I have my facts correct. While I’ve read a number of the papers in this area, I’m sure you know more about the subject than I do. Thanks for all your comments.