Guest Post by Willis Eschenbach
In three previous posts here, here, and here, I discussed problems with the paper by Shakun et al., “Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation” (PDF,hereinafter S2012)
Commenters said, and reasonably so, that I had not fully addressed their claim that warming progressed from south to north. Their Figure 5a shows the trends by latitude band. It purports to show that the further north, the later the warming.
Figure 1. Figure 5a from S2012. ORIGINAL CAPTION: Figure 5 | Temperature change before increase in CO2 concentration. a, Linear temperature trends in the proxy records from 21.5–19 kyr ago (red) and 19–17.5 kyr ago (blue) averaged in 10° latitude bins with 1 sigma uncertainties.
Now, that seems pretty clear. Less blue and more red as you go up towards the north pole. What could be wrong with that? Well, as usual, nature is not that neat. When you look at it closely, it’s nowhere near as clear as that chart seems to indicate.
The first thing that’s wrong is that out of the fourteen bands with data, only five of them show a significant difference between the early trends (21.5 to 19 thousand years ago [kyr BP]) and the late trends (19 to 17.5 thousand years ago [kyr BP]). In the other nine bands, the uncertainties overlap, so we can’t even say if they are different. (The uncertainties for each band are shown as red and blue long thin lines with short vertical ends.) As a result, they are meaningless, and should not be shown.
But that’s just a symptom of the real problem, which is that there is very little data in many latitude bands, and the proxies are very different from each other.
To investigate each of the bands, I started by expressing all of the temperatures as anomalies around the average temperature from 21.5 to 17.5 kyr BP. Then I divided them by bands and graphed them. Figure 2 shows the results for the Northern Hemisphere.
Figure 2. Trends by latitude band. The background colors correspond with Figure 1, with red for 21.5 to 19 kyr BP, and blue for 19 to 17.5 kyr BP. Dark red lines are centered Gaussian averages of the individual proxies, with the data shown by the green squares.
Let me discuss these panel by panel. First, let me note an oddity—why is the early period longer than the later period? But I digress …
Panel a: Only two proxies, and one of them has a hump right at 19 kyr BP.
Panel b: Five proxies. Three have a hump right at 19 kyr BP.
Panel c: Two proxies. One is dead level, one rises during the later (blue) period.
Panel d: Three proxies, but one of them starts just before 19 kyr BP. Seriously, folks, do you think an average of these is meaningful?
Panel e: Hard to tell what’s happening here. Several of the proxies go either up or down just after 19 kyr BP.
Panel f: All trends in the blue section are about the same, except the poor proxy taking a dive right after 19 kyr BP
Panel g: Another goofy one. Right after 19 kyr BP, two of the proxies head for the sky.
Panel h: No trend before, no trend after.
Figure 3. As in Figure 2, but for the Southern Hemisphere
Again, by panel.
Panel a: Not much difference, red or blue period.
Panel b: Three proxies. Two go up at 19 kyr BP. One goes down at 19 kyr BP. Is this supposed to be meaningful?
Panel c: Three proxies. Neither the red period nor the blue period shows much.
Panel d: Two proxies. Two. One goes up after 19 kyr BP. So what?
Panel e: Here, a lot of the proxies have a low point at about 19 kyr BP … and they have a high point about 500 years before that.
Panel f: These four, all ice cores from Antarctica, agree pretty well. However, only one of them has a significant trend, and that only in the blue area.
Now, to me those results don’t mean much. Of the eighty proxies, only eight of them have a significant trend in both the red and blue periods … and that’s without adjusting for autocorrelation. The proxies show no clear pattern. They are too varied, and too few, to tell us much of anything.
Let me close with what may be a more revealing graph, dividing the globe up into 45° latitudinal bands.
Figure 4. S2012 proxies divided into four bands. Colors go from blue at the north pole, to yellow at the equator, and end up with red at the south pole.
Let me say that Panel a shows something very curious. The rise in temperature started quite early the two Greenland proxies … and timing of the others are all over the map. I can’t see how that supports any claim of late warming in the north.
BOTTOM LINE: I see no evidence in any these latitudinal bands of proxies to support the claim that the warming progressed northwards. It certainly may have done so … but these proxies are not useful for supporting that claim.
My goodness, I certainly hope that I’m done with these proxies.
w.
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You would expect warming coming out of glaciation to show a latitudinal pattern. The ice sheets covering the northern hemisphere would have made it warm at a different rate to the south. In the south extra energy would show up pretty much straight away as increased temperature. In the north it would melt ice first. Consider two pitchers, one with mostly water and a little bit of ice, and one with a lot of ice. Put them in a warm room. The one with more ice will warm slower. In fact temperatures will not rise much in that pitcher until the ice is all melted so if you were only looking at a record of temperatures you might think there was nothing much going on in that pitcher in the time that the ice was busy melting.
Even if the North warmed after the south, which is at least plausible, the south started warming before CO2 levels rose. The temperature rise in the North may have been delayed because the ice had to melt first. Only once the ice was mostly gone would the temperatures in the north have started to kick up to modern levels. That means there would have been melting going on in the north before the main part of the temperature rise started, which would make it before the CO2 rise. What warmed the south and melted the ice in the North in the time before CO2 levels started to kick up. CO2 didn’t do it.
This Shakun study if I am correct in its assumptions, says that heat from the south oozed its way to the north over time. It has been cooling down here in the south for some time, is that the cold from the north, oozing down to the south, or is our cold about to ooze up to the northern climes?
Willis, I wrote a grant and one of the key components was to use a very specific, yet robust and obscure assay system. I had already tested it and validated it. The grant was rejected.
18 months later a paper was published by a competitor, the Prince of Darkness, using exactly the same methodology I had proposed to examine exactly the same thing.
I submitted a paper a while ago to AGU about how to handle gaussian or other averaging at the beginning and end of the dataset. It discussed Michael Mann’s crazy ideas about how to handle averaging at the beginning and end.
They rejected my paper. Six months later Mike Mann wrote a slightly changed version of my paper and AGU published it. You can’t convince me that a) I didn’t get published because of my unorthodox beliefs, or that b) one of the reviewers didn’t give my paper to Mann, who saw that I had eviscerated his previous ideas, so Mann claimed my work as his own. Pathetic.
Wow. Can you document this, that is, do you have the reviewers comments and original submission in hand? I would think that this warrants a strong letter to the editorial board and publishing board of this journal. If, in fact, Mann was one of the reviewers (or good friends of one of the reviewers) this is a most serious charge.
rgb
rgb – sorry, I should clarify that I don’t agree you wouldn’t necessarily be inclined reject it!
The point is that one should not reject a paper because you disagree with its conclusions. You might reject it because the science in it is badly done or poorly presented. Those aren’t the same thing. If I refereed a paper (say) that claimed that a certain body of observational evidence drawn from red-shift determined rotational velocities of orbits in distant galaxies was proof of the existence of dark matter, I would not be justified in rejecting the paper just because I personally don’t believe that “dark matter” (a new kind of matter that exists in great profusion but that doesn’t couple to the electromagnetic field for some reason) exists. I would be justified in asking for a revision if the paper didn’t fairly consider alternative theories. I would very much be justified in rejecting the paper if it made actual errors in its mathematical analysis or made unjustifiable assumptions about the data in order to arrive at its conclusion.
On this basis, the referees of the Shakun paper might well have been justified in asking for some revision, in particular for a less biased presentation of the alternative theories wherein CO_2 is a minor driver rather than the major one and for some sort of explicit quantitative support for any alleged mechanism wherein it is a major one. In particular, failing to address the YD is a serious problem. Failing to address the obvious coastal bias of the sites is a problem. Failing to note the lack of resolvable correlation in much of the data is a problem, but not one that a referee is likely to pick up.
A referee is absolutely not likely to or responsible for going back to all of the original data and replotting it with an eye to disproving the paper being reviewed in order to reject it. In fact, this is borderline inappropriate — a referee is not supposed to steal ideas or co-opt a method at the review stage, reject a paper, and then publish later (which is why Willis has a serious case against AGU above).
However, a referee is well within their rights to accept a paper they might disagree with (after raising their objections with the authors and being ignored) or to recommend rejection but be overridden by the editor (as might well happen because the editor is not supposed to be “involved” in the science review or to take sides in a controversial issue) and then write their own paper presenting their side of the story! In fact, that is good science, whether or not a scientist is a reviewer. Reviewers simply get to see the papers in question first — the advantage of being a reviewer — and hence are more likely to be first to submit just this sort of paper either extending or rejecting any given finding.
rgb
rgbatduke says:
April 12, 2012 at 7:56 am
I concur, but I wasn’t meaning you would reject through disagreement either – I was meaning I would anticpate that you would do a reasonable job of assessing it and finding it wanting! My primary point was that the peer review process by either referee(s) or reviewers was inadequate in this case IMHO. The reviewer has a ‘duty of care’ to assess the content objectively in order for it be presented for general publication. Yes, they may request a clarification or minor alteration on points – but they must reasonably assess the scientific content, not just that the conclusions ‘drawn’ from the paper are acceptable – which in this particular cases, also seem somewhat stretched – as Willis has amply, and somewhat easily, demonstrated!
What Ian H says on April 11, 2012 at 9:20 pm about the delay in detectable warming rate in the northern hemisphere seems quite logical – as far as I can see.
As a matter of fact places like Greenland, Svalbard and “Perma-Frosted” Siberia can be said to still be in an “Ice Age”. – Which is why some people like to point out that the Holocene is just one of the many short “Interglacial periods” during the present Ice Age which started some 2,5 – 3 million years ago (or YBP).
So, as far as “Trumping the Sun” the chances are that CO2 didn’t do it – and never will.
Isn’t there a fundamental chemistry problem here? You are looking at latitudes and using oxygen and carbon isotopes as proxies. How do you correct for the chemical differences in each latitudinal band? The southern hemisphere has much more water than the northern hemisphere. Wouldn’t this distort your results when you sort them out by latitude? I am not paying to read the paper, I can’t afford it. My question is, was that addressed? How?
rgbatduke says: April 12, 2012 at 7:38 am
I second this proposal.
Mann seems to be of particularly despicable character, and the alleged act adds to his despicability. He should be held to account.