A reply to Shakun et al – Dr. Munchausen Explains Science By Proxy

Guest Post by Willis Eschenbach

There’s a new study entitled “Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation”, Shakun et al. (paywalled, hereinafter Shakun2012). The paper claims to show that in the warming since the last ice age, CO2 leads temperature. Anthony wrote about it in his post “A new paper in Nature suggests CO2 leads temperature, but has some serious problems“. The press release says (emphasis mine):

A new study, funded by the National Science Foundation and published in the journal Nature, identifies this relationship and provides compelling evidence that rising CO2 caused much of the global warming.

Lead author Jeremy Shakun, who conducted much of the research as a doctoral student at Oregon State University, said the key to understanding the role of CO2 is to reconstruct globally averaged temperature changes during the end of the last Ice Age, which contrasts with previous efforts that only compared local temperatures in Antarctica to carbon dioxide levels.

“Carbon dioxide has been suspected as an important factor in ending the last Ice Age, but its exact role has always been unclear because rising temperatures reflected in Antarctic ice cores came before rising levels of CO2,” said Shakun, who is a National Oceanic and Atmospheric Administration (NOAA) Post-doctoral Fellow at Harvard University and Columbia University.

“But if you reconstruct temperatures on a global scale – and not just examine Antarctic temperatures – it becomes apparent that the CO2 change slightly preceded much of the global warming, and this means the global greenhouse effect had an important role in driving up global temperatures and bringing the planet out of the last Ice Age,” Shakun added.

The good news about the paper is that they have provided the temperature records (Excel spreadsheet) for the 80 proxies used in the study. My compliments to them.

Me being a suspicious fellow, however, I figured “trust but verify”, so I plotted up the temperature records that they used. I always begin with the original data, without any additions or distractions. Figure 1 shows the data that they used.

Figure 1. Records and types of proxies used in the Shakun2012 study 

As you can see, some of the ice core records are down where we’d expect them to be, well below zero. Those are the GRIP and NGRIP records from Greenland. But there are some oddities about these proxies.

One problem that is immediately obvious is the timing. The peaks for the previous interglacial period (the Eemian, about 130,000 BC) don’t line up. That may not be much of a problem, though, because the paper is about the warming from the most recent ice age.

One oddity is that there are ice core records that are right around freezing (0°C). In addition, there are pollen records around freezing as well. This shows that we actually have a mix of anomaly records and actual temperature records. This is not a problem, just an oddity.

Next, let’s take a look at the location of the proxies. Figure 2 is from their paper:

Figure 2. Location of the proxies used in the Shakun2012 study. 

 This looks good, it looks like there may be passable coverage. So let’s look at the last glacial transition, we’ll look at the time since 26,000 BC.

Figure 3. Same data as in Figure 1, but showing the warming from the last ice age.

Here, you can see the Antarctic ice core records (yellow and green lines near 0°C) mentioned above that are shown as variations, with the modern value taken to be 0°C.

Some other observations. Greenland (yellow temperatures at bottom) seems to be an outlier in terms of change in temperature. The Antarctic ice cores and all of the rest of the records show much less warming since the ice age.

In order to compare these eighty proxies to each other, what we need to do is to “standardize” them. This means to first subtract the mean (average) of each proxy from the individual values. Then each of the individual values is divided by the standard deviation of the entire record for that proxy. The result will vary between about -3 and 3. Standardizing preserves the shape and timing of the data, it just makes all the proxies have a mean of 0 and a standard deviation of 1.

Next comes the part that the authors of these multi-proxy studies seem to have generally ignored. This is to look at each and every one of these proxy records and think about what they seem to mean. I’ll look at them sixteen at a time. Figure 3 shows the first sixteen of the Shakun2012 proxies.

Figure 4. Proxies from the Shakur2012 study. All of these cover the period from 26,000 BC to 1980 AD. Vertical dashed lines show the minimum (light blue) and maximum (dark red) values for the each proxy. Minimum and maximum times rounded to nearest 100 years. Colors as shown in Figure 1. Click for larger version.


1, 2: These are the Greenland ice cores. They show a warming of 32 and 27 degrees respectively, which is much more than any other proxy. Warming begins earlier than 20,000 BC.

4: The warmest date is at 1200 AD.

6: Warmest date is 1000 AD. Warming doesn’t start until 12,600 BC.

9: Maximum warmth is at 14,600 BC.

15: Very unusual shape, 11° warming.

Figure 5. Same as Figure 4, proxies from the Shakur2012 study. All of these cover the period from 26,000 BC to 1980 AD. Vertical dashed lines show the minimum (light blue) and maximum (dark red) values for the each proxy. Minimum and maximum times rounded to nearest 100 years. Click for larger version.

19: Warming doesn’t start until 10,800 BC

21: Maximum warmth precedes maximum cold.

28. Maximum doesn’t occur until 400 BC.

30. Maximum doesn’t occur until 1400 AD.

31. Maximum doesn’t occur until 2400 BC.

32. Maximum doesn’t occur until 1500 AD.

Figure 6. Same as Figure 4. Click for larger version.

34: Maximum at 1600 AD

35: Maximum at 14,000 BC

36: Strange shape, constant warming until the present.

42. Maximum not until 400 AD.

44: Warming until the end of the record in 8200 BC.

Figure 7. Same as Figure 4. Click for larger version.

50: Maximum not until 1100 AD.

51: Constant rise beginning to end.

52: Large drop and rise after maximum warmth.

53: Rises beginning to end.

54: Rises beginning to end.

58: Maximum not until 1300 AD.

59: Maximum not until 1600 AD.

60: Large rise in 1100-1200

Figure 8. Same as Figure 4. Click for larger version.

67: Warming starts at 25,900 BC.

68: Warming only one tenth of a degree

76: Warming occurs almost instantaneously


The variety in the shapes of these graphs is quite surprising. Yes, they’re all vaguely alike … but that’s about all.

The main curiosity about these, other than the wide variety of amounts of warming, is the different timing of the warming. In some proxies it starts in 25,000 BC, in others it starts in 15,000 BC. Sometimes the warming peaks as early as  14,000 BC, and sometimes around 5,000 BC or later. Sometimes the warming continues right up to the present.

The problem becomes evident when we plot all of these 80 standardized proxies together. Figure 9 shows all of the standardized temperature traces.

Figure 9. All 80 temperature proxies from Shakun2012. Colors as shown in Figure 1.

Now, there’s plenty of things of interest in there. It’s clear that there is warming since the last ice age. The median value for the warming is 4.3°C, although the range is quite wide.

But if you want to make the claim that CO2 precedes the warming?

I fear that this set of proxies is perfectly useless for that. How on earth could you claim anything about the timing of the warming from this group of proxies? It’s all over the map.

Final Conclusion

The reviewers should have taken the time to plot the proxies … but then, the authors should have taken the time to plot the proxies.


[UPDATE] A hat tip to Jostein, who pointed in the comments to the Shakun Nature paper being available here.

[UPDATE] Some folks wanted to see the CO2 data they used on the same timescale. Other folks said the colors in Figure 9 were misleading, since ice cores were printed on top, obscuring others below. We’re a full-service website, so here’s both in one:

Figure 10. All proxies, along with CO2 record used in Shakun2012.

My best to all,



I decided to take a look at the various proxies by proxy type. There are ten different kinds of proxies.

Figure 11. Proxies averaged by type.

A few notes, in no particular order. The ice core records are similar, but the timing is different.

Foram assemblages seem to be useless. The same is true of the Tex86 proxies.

Pollen has a consistent signal, but the warming doesn’t start until about 10,000 BC.

MBT/CBT perfectly exemplifies the problems with this approach. Which one are we supposed to believe? Which one is it that is lagging the CO2?

Finally, the Mg/Ca and the UK’37 proxies kinda sorta have the same shape, but no uniformity at all regarding the timing of the rise.

Let me close with a black-and-white version of the above chart. This allows you to see where the denser areas are located.

 Figure 12. Proxies by type. Blue line shows CO2 data as used in the study. 

Note the difference in the underlying shapes of the different types of proxies, and the differences in their timing with respect to the rise of CO2.

Next, note that the CO2 record they are using is from Antarctica. That is the reason for the good fit with the single “ice core ∂18O and dD” proxy (left graph, second row) and the “ice core dD” (center graph, second row). Both of those are Antarctic records as well.

Also, as you can see, even within each proxy type there is no unanimity regarding the timing of either the onset or the end of the warming from the last ice age.

CO2 is the blue line … so was the warming before or after the blue line?


[UPDATE]—The discussion continues at Shakun Redux: Master tricksed us! I told you he was tricksy!


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Brilliant as usual


The reviewers should have taken the time to plot the proxies … but then, the authors should have taken the time to plot the proxies.
Willis, there’s a good chance they don’t know how…..
….or it’s just more sloppy hurry up and publish rent seekers


I think I can see the face of Jesus in the Fig 9 plot! /sarc


Incredible work, Willis! Looking at the scatter plot, it seems the warming of that dotty mass of mess begins around 20k BC, which is before the CO2 raise.
In any case, this data is so all over the map, there’s no way to say anything about the order of timings. Maybe there’s a difference in timings based on the source of the proxie? But, when I look at say Mg/Ca, there you have some showing warming starting before 20k BC and some starting 15k BC. So even there it’s inconsistent…


Nice deconstruction, Willis. Are you working on the CO2 data as well?

Can they really date these proxies to within 100 years or so, back to 12000BC? If not, then surely their whole case falls apart.

Ed Scott

April5, 2012
Climategate Heads to Court
By S. Fred Singer
As a climate scientist, I am quite familiar with the background facts that Prof Michael E. Mann (now at Penn State U) so shamelessly distorts in his new book The Hockey Stick and the Climate Wars: Dispatches from the Front Lines.


So which invidual proxies lag or lead the rise in CO2? Which cross over at some point?

Louis Hooffstetter

Thanks again Willis!

“Final Conclusion
The reviewers should have taken the time to plot the proxies … but then, the authors should have taken the time to plot the proxies.
No, no Willis, the whole “International Antarctic Research Team” will be packing their bags for the last time now that they have been proven to be of no use whatsoever!??


Willis – Excellent deconstruction, as always. Wonderfully informative graphics. Tufte would be impressed.
How has Shakun responded to your analysis?

Bloke down the pub

A little bit of smoke and mirrors and an unsubstantiated claim, but it was all that was needed to keep the msm on message. Keep asking the right questions Willis.

Seems that the authors and reviewers did more plodding than plotting.

Joe Public

Thank you, W, for taking the time to plot the proxies so us public have a better understanding of the data.

Al Gore was caught lying about this timing by British courts. Willis, It is my layman’s understanding that seawater, as it warms, releases CO2 dissolved therein. As seawater warms it’s ability to keep CO2 in solution decreases. This leaching of CO2 as the oceans warm is a great explanation for the correlation between temperature and atmospheric CO2 concentration. It explains why CO2 lags warming. Warming first then atmospheric CO2 increase.
This is provable in a laboratory. Yet no mention of it in this “Shakun2012” paper.


They definately stretched things a long way to make CO2 the culprit. Their data does not support their conclusion.

Coach Springer

Anthony’s first post on Shakun2012 provoked a lot of non-analytical reaction. Thanks for this bit of analysis. It seems a more direct statement of conclusion of the study would be that the take they are emphasizing is only one way of looking at a bunch of proxies and any one way is a bit of a stretch due to the huge variance. This study doesn’t seem to move the debate as much today as it did when I first saw it.
Still stuck with subjective statistical analysis and a rule of non-empirical science that all ties and everything short of valid upset (upwards of 90% “certainty”) of a null hypothesis goes to the null hypothesis.

Josh Grella

Thank you once again for doing the due diligence the researchers and reviewers should have done on the first place. This is yet another example of the blinded leading the blinded and is so typical of the pseudoscience that is rampant in climate scientology.

Interstellar Bill

The proxies that don’t support the CO2-causation meme are averaged out, or…


Willis, once again thank you for being you. You use data to draw conclusions with no arm waving. You have not shown the carbon dioxide data but I agree that there is no way to draw any meaningful conclusion about the relative timing of temperature and carbon dioxide concentrations in the atmosphere from this data set.
I note an oddity in figure 9 at about -14000 years. The yellow (ice core) data quickly change, relatively speaking, down to minus 1.3 then up to plus 1.3 standard deviations. The same type thing happens at – 11000 years with an even wider swing. There is also another hint at – 26000 years. There was a geology paper about three years ago detailing a very rapid 10 to 15 F increase in one or two decades in Greenland about 14000 years ago. There must be some natural event that causes these departures in temperature. If carbon dioxide were the root cause, it seems to me it would take extreme volcanism, which would be well known from trace markers around the globe.

Ed of Mesa

– It is hard to tell to much from figure 9 since proxies that were graphed later may obscure earlier ones. Not to mention that the yellow catches the eye.
– It looks like from -15000 to -8000 there was an accelerating increase. From -8000 on there was a slower decrease.
– If you averaged all the values for a time and then graphed the average would it show anything useful about the general trend of the data.


I would have liked to see the CO2 levels indicated on the final plotting. I think you also demonstrated that some of these proxies are in fact not proxies at all. On the other hand, the ice core proxies seem remarkably consistent. A bit of research into the accuracy of ice core proxies would be worthwhile.


Just more post-normal science (fit the data to the theory). Truly nothing to see here folks; run along.
(However, it is part and parcel in keeping with the CAGWCF (“Control Freaks”) meme they keep pitching.)


TRM said:
They definately stretched things a long way to make CO2 the culprit. Their data does not support their conclusion.
But in the world of AGW “Science” data says whatever they want it to say or it is adjusted accordingly. There hope that explains it for you.
PS can’t wait for the rebuttal adjusted data analysis. Say anyone want to bet on the chance of any of the above information ever seeing the pages of Nature?


Me being a suspicious fellow, however, I figured “trust but verify”
haha, these Global Warming nuts are even worse than the old Soviets though so you may have to ratchet up your level of suspicion to compensate

Michael Cohen

Would it be possible to superimpose CO2 (with error bars) for the same interval on top of the scatter plot? That would make a compelling image.


Willis, it’s reasonably easy to bring the WUWT final data-plot into excellent agreement with the main data-plot of Shakun2012:
Step 1: Color-code the WUWT time series into northern-and-southern hemisphere proxies, per Shakun2012’s figures 2B and S-28AB (the latter figure is in their 51-page Supplemental Information).
Step 2: Include the CO2 data, per Shakun2012 Figures 2A
Summary: The WUWT/Eschenbach analysis of the temperature/CO2 data stands in good agreement with the Nature/Shakun article. In aggregate, the global data provide no evidence that temperature increases precede CO2 increases.

Robert M

This reminds me of Steig et al 2009. The AGW fraudsters NEEDED the Antarctic to “warm” as per hysterical predictions. And abracadabra Eric Steig whipped some warming out of his hat. The news media breathlessly (and credulously) reported the study “results”. The study was soon shown to nothing more then an exercise of data manipulation, and proven to be one fantastical error after another. The authors claimed they were incompetent, not fraudulent, and the media promptly forgot the whole thing ever happened. Of course AGW supporters already had their headlines. This study has the same flavor.

You should know better than to suggest that a value is the “maximum” for a proxy without establishing the uncertainty. Thats the kind of crap I expect from Hansen and his temperature records.

I’d like to see the proxies they considered but discarded, because the ones they picked certainly don’t prove anything other than the interglacial started.


Nice post. Science should be “here’s what we know” Not “here’s what we want to conclude, and we’ll present the data in a manner to support our preconceived notions”.
We know it warmed, and you show that we have a hard time saying exactly when.

These proxies make me think of global warming data.
Lets say you are making hamburgers and you take 30% frozen ground beef (representing the cooling stations) and say 30% overcooked ground beef (representing the stations warming way more than .2C/decade) and then you take the 40% of the stations warming less than .2C/per decade.
Then you throw them all in a meat grinder.
Mosher would suggest the burgers are perfectly cooked.
The authors of this paper suggest the meat grinders proxies prove something about CO2 leading temperatures.
I wouldn’t.


LOL @ Steven Mosher
All of a sudden you are extolling the size of ‘uncertainty’ ? What a laugh. The fact is that in almost ALL surface station data as in proxy data, “uncertainly” and limits of observability are likely to be much larger than the ‘signal’ extracted.


I submit another vote to overlay the CO2 data on the final plot. Please.

Nice punchline, Willis. Too bad members of the orthodoxy are not allowed to think for themselves. They might save themselves some embarrassment.


I like Figure 9, it reminds me of a Rorschach Test. I can see what I am pre-disposed to seeing.
In my case, a vomited rainbow.

I thought all data was good, Steve.


You are really overreacting here, and missing the entire point.
The maximum temperature for any of the plots isn’t under discussion, it’s the timing of when temperature starts to raise. And that’s scattered all over the place, refuting the conclusions of the paper that used this data, quite spectacularly.

Septic Matthew/Matthew R Marler

Good post. Submit as a letter to Nature and see what happens. Send a copy to the authors. They’ll probably be mad that you posted it before alerting them, but maybe not.

Willis your Maunchasen by proxy allusion makes me sick! (I think perhaps Willis and about a 1/2 dozen people are laughing now…)
I’m the happiest sick relative you have…!

Steve from Rockwood

Willis. Great work as usual. Your Figure 1 and Figure 3 show just how noisy these proxies can be. I’m not sure that minimums and maximums mean anything given the noise levels of each proxy. But there is a definite cool to warm trend and it would be interesting to calculate the inflection point of this trend for each proxy, to then take the average inflection time and subtract each from the average to see how variable the time of transition from cool to warm is for each proxy. If, for example, they vary by many centuries, then how could you possibly rely on them for a correlation with a lag time with CO2.
What bothers me about the proxies is the variation in transition time from cool to warm. Proxy 67 shows a gradual warming over thousands of years while proxy 76 shows a shorter transition over centuries. Proxy 73 is garbage as are many more, making Figure 2 (location map) misleading.
Figure 9 is a bit tough to appreciate. Perhaps if all the points had the same color people would realize how much error there is in the data sets.
But thanks again Willis for showing us how ugly the raw data is. GI = GO.

Septic Matthew/Matthew R Marler

Steven Mosher: You should know better than to suggest that a value is the “maximum” for a proxy without establishing the uncertainty. Thats the kind of crap I expect from Hansen and his temperature records.
That’s a fair comment. You beat me to it. Establishing “maxima” by eyeballing and contrasting them does not show that much. When the paper comes out from behind the paywall, we’ll be able to compare Willis’s methods to the authors’ methods in detail.
Also, it is good that the authors provided their full data set.
To amend my previous post, Willis should probably obtain a copy of the paper from the authors before submitting a letter to Nature, assuming he has any interest at all in my suggestion.


My first reaction to the study (I have no vested interest in assuming a major role for CO2 in climate changes): what if a large portion of added (sun) heat was being initially sequestered deep into oceans (as per the current Trenberth theories), releasing great quantities of CO2 in the process. This “sequestered’ heat would eventually make to the surface at different times, different places depending on the ocean currents of the time, which was the main driver of local temperatures around the globe. It seems more plausible to me that atmospheric temperatures around the world would be impacted primarily by changes in surface water temperatures than changes in CO2 concentration although the additional CO2 acted as a positive feedback. I think the study (minus the misdirected hype) will ultimately have a positive effect on science. It’s great to have more data since it only confirms what others have been saying years that causes of climate changes are rather complex.

Scott Brim

Steven Mosher says:
April 6, 2012 at 9:23 am
You should know better than to suggest that a value is the “maximum” for a proxy without establishing the uncertainty. That’s the kind of crap I expect from Hansen and his temperature records.

Steven, as an educational service for the WUWT readership, could you provide us with a high level description as to what kind of methodology should be used to establish the uncertainty?
How would uncertainty be defined in precise terms? What kinds of factors — statistical factors, systematic measurement error factors, and physical science factors — would go into establishing the uncertainty? What kind of approach would be employed to integrate these various factors in ways which can reliably establish an uncertainty?

John T

“Next, let’s take a look at the location of the proxies. ”
Probably just a curiosity, but what I immediately noticed was, other than ice cores, they’re all coastal locations (a few mid-Atlantic?).

Why does the eyeball trend of the scattergram appear to be heading down since around 8000 BP? I thought temps were rising since the deglaciation?


The warming arguably begins in 15,000 BCE, but, as you so brilliantly point out, it is all over the map, all over the map. If there was one unifying observation one could draw from the holocene part of the data, it is the holocene optimum occurred roughly 8000 years ago, which corresponds well to the last time the sun was as active as it was in the 20th century, at least according to some of the papers I’ve read. But not Leif, apparently.

Steve Oregon

“The reviewers should have taken the time to plot the proxies … but then, the authors should have taken the time to plot the proxies.”
I’m sure they are working on it.
Or they did but realized the results were not useful so they told themselves “never mind” with that stuff, we have a story to tell”.

Munchausen Syndrome by Proxy? Careful – you’re banging on hornet nests!
The New Hampshire Child Protective Services agency (DCYF) has tried alleging that against some of my wife’s clients. (Or conversely, ignore a diagnosis of Osteogenesis Imperfecta.) MSBP is something where the mother (they have different attacks for the fathers) makes the kid sick so she can look like a hero when she gets medical treatment for the kid.
I guess in the climate “science” arena, the closest analog would be alarmists convincing everyone that we are destroying the environment so the can look like heroes when alternative energy, green power, and a return to the 18th century saves the day.
There’s MAMA, Mothers Against Munchausen Syndrome by Proxy Allegations. Perhaps we can get Anthony to rename this blog WUWU – Watts Up with Unknowns.

Martin A

“It’s clear that there is warming since the last ice age. ”
Is this an unexpected result?