the Air Vent

Because the world needs another opinion

I can’t hear you

Posted by Jeff Id on December 2, 2011

This email demonstrates again exactly why hockey stick temperature curves are all crap.

Bo Christiansen wrote an email (copy below)  on March 16 2009, stating in no uncertain terms, what I have written here dozens of times.  You can’t regress extremely noisy data on a short series (temperature range) and then project it 2000 years into the past.  When the noise approaches the level of (or in the case of paleowhackology, actually dominates over) the signal, you will have a loss of variance in the historic signal in comparison to the calibration range.   Loss of variance means, no big changes in historic temp.  It seems pretty obvious to me that this is what happens, but in the paleo world, it is nearly completely ignored.  The problem is so severe that Mann published a paper in 07 which attempts to cover it up.  I use the words, ‘cover it up’ with care as it is based on a lot of experiences and it is my true opinion. Unsurprisingly, he used artificial data which conveniently had the right kind of noise and as so often happens in paleoclimate – he just barely missed detecting the problem.

What it means is that your little ice age (LIA) and your medeival warm period (MWP) in EVERY reconstruction I’ve seen are actually more extreme than shown.  My estimates are that they are muted by as much as 50%.  This is not a minor issue for the hockey stick poster boy of climate science or the science in general because the models follow the hockey sticks.

Now there are papers where these kinds of methods aren’t used.  Ljungqvist’s work for example.  The problem with these though (besides the fact that I don’t believe the data has much temperature signal in it at all) is that they use known “temperature sensitive” proxies.  These are noisy proxies which  have been pre-sorted by people over the years because of their correlation to temperature.  It is therefore the same thing as the regression methods except it is done inadvertently by hand.

Most reconstruction papers ignore these obvious facts just as they have pretended to ignore this blog but Bo Christiansen has published what is a paleo-nightmare.  What we learned from this email release is that he took the time to communicate it to many of his colleagues for which I’m sure he has gained little popularity. Think of the guts that took to publish this paper and then communicate it to the team after the Soon and Baliunas attacks.

There are no responses to this email that I can find in the released documents.

date: Mon, 16 Mar 2009 14:08:31 +0100
from: Bo Christiansen <>
subject: Paper on climate reconstructions
to:,,,,,,,,,,,,,,,,,,, Juerg Luterbacher , Andrew Weaver , Alexey Kaplan ,,,,,,,,,,,,, Peter Thejll , Torben Schmith ,,

Dear All,

Our paper “A surrogate ensemble study of climate reconstruction methods:
Stochasticity and robustness” has now been published in J. Clim.

It is here:

or here

A VERY brief summary:

1) Seven different reconstruction methods are tested
 on the same data. These methods include both direct reconstructions
of the NH mean temperature and field reconstruction methods.
The field methods include both the original method of Mann et al. 1998,
the RegEM Ridge and RegEM TTLS methods used in more recent work.

2) We use a field surrogate method to estimate the stochasticity that
is always present in regression methods.

 1) All methods strongly underestimates the amplitude of
 low-frequency variability and trends. This means that
 it is almost impossible to conclude from reconstruction studies that
 the present period is warmer than any period in the
 reconstructed period.

2) There is a large element of chance in the reconstructions.
This might also explain some of the opposing results obtained
in previous studies.

In a new paper we have submitted to J. Clim. (under review) we
use the the same methodology to test sea level reconstruction methods.
The paper is here:

These methods are closely related to the temperature reconstruction methods.
Now tide-gauge measurements take the place of temperature proxies,
and satellite altimetry the place of temperature observations.
For the sea level reconstructions the situation is simpler than for
temperature reconstructions because the tide gauges are direct measurements
of sea level and do not include noise. We can therefore easier
identify the sources of the errors in the reconstructions
and stratify the errors  into contributions from limited spatial coverage
of gauges and non-stationarity of the sea level field.

Best wishes -Bo

Bo is right on all counts and the hockeysticks of paleoclimate should be dead for IPCC AR5.   My guess is that the HS poster boy will be front and center so everyone can be properly afraid.  Bo Christiansen also took the time to post on this paper at Eduardo Zorita’s blog and allowed a guest post here.

[lalalala – insert I can’t hear you cartoons here]

12 Responses to “I can’t hear you”

  1. Jeff Id said


  2. Chuckles said

    Love it.

  3. Marion said

    Perhaps they were thinking of those climate science grants on offer ……

  4. Matthew W said


    That’s great !!!

  5. Matthew W said

    Can this be explained and is it important?

    2) There is a large element of chance in the reconstructions.
    This might also explain some of the opposing results obtained
    in previous studies.

  6. George said

    Bo says “The climate sensitivity is a measure how how much the surface temperature changes given a specified forcing. A larger climate sensitivity could mean that the estimates of the future climate changes due to increased levels of green-house gases are underestimated.” He concludes that climate sensitivity is “greater” than we think it is but then jumps to the conclusion that it is greenhouse gases that it is sensitive to. It might be something completely different. It may not be CO2 sensitivity at all. The climate may not be nearly as sensitive to CO2 as we believe it is but much more sensitive to small changes in cloud cover, we just can’t be sure at this point. I wonder if he added those last two sentences in his guest post Eduardo Zorita’s in order to deflect criticism from “The Cause”. The idea being that he figures he can trash RegM as long as he adds a “it’s worse than we thought” at the end.

  7. George said

    So, what happens when Mann’s data are run through Bo’s maths? What does that look like?

  8. denis christianson said

    Dr. Mann left his paleopast behind and is now working on the next hockey stick. It is one that extends into a future of disease and pestilence driven by a warmer future. He was granted another two million Obamabucks in the stimulus act to produce this advocacy research.

  9. Steve Garcia said

    Reading up the last few days on the divergence problem with tree-rings, it seems that the tree-ring>temperature proxy meme doesn’t hold. It certainly hasn’t held for the last 70 years. It makes n sense that any climatologist thinks they can do a deconstruction based on a proxy that can’t be made to calibrate well with the instrument data during that long in the overlap period.

    That 70 years of divergence includes the entire cool-down of 1940-1975, plus the entire warming from 1975-1998, and is still diverging. So, no one can make an argument that there is some kind of ceiling or threshold that tree-rings can’t get past. The cooling down period was when the divergence began, and since the temps were steadily declining, the threshold was farther and farther from the temps indicated. A ceiling doesn’t affect tree-rings when the temps aren’t even reaching the hypothesized ceiling.

    Based on the slope of the decline that Briffa tried to hide – 0.4C from the start, but much more later on, toward 1998 – tree-rings simply aren’t working as proxies anymore. And if they aren’t then no one can use them as proxies for the non-divergent period(s) either. Claims that tree-rings are proxies simply cannot hold water.

    And since tree-rings are the bulk of proxy data (and, I believe tree-rings were used to calibrate other proxies like corals and ice cores), one has to ask if any of the non-instrument data is worth anything at all. Plugging in proxy data into any reconstructions seems more and more like bad science, wrong science. One can plug the numbers into the reconstructions, but if there is no linearity between tree-rings and temps, what is the point? It literally is GIGO.

    If one plugged the REAL tree-ring converted temps (as opposed to the instrument data since 1940) into the reconstructions, the reconstructions would not show warming at all, based on the amount of divergence everyone is seeing. Why this is not itself the biggest issue in climate science, I have no idea. Steve M pointed out the “hiding of the decline” even before Climategate 1.0, and the CG1.0 emails confirmed this. Now there are multitudes of CG2.0 emails that discuss this, and everyone is acting like, “Well, the reconstructions are still somewhat correct.”

    But that doesn’t follow at all.

    If we deducted even the 0.4C from the 1990 graphs, there would basically be little warming shown at all. And if we plug in the 0.8C decline in the late 1990s (vs the instrument record shown) – see Fig 3 in Steve M’s post – the graph would show the global average at about 1910 levels. That is IF they still trusted the tree-rings. BUT THEY DON’T trust them anymore. That was the reason for “hide the decline” in the first place. And if they don’t trust them NOW, what is everyone doing trusting them about the pre-instrument period? Who is dumber, them for putting up these flawed reconstructions, or everyone else for giving the reconstructions any weight at all?

    Jeff, you say, “My estimates are that they are muted by as much as 50%.” Based on the divergence, the MWP could have been just about anything at all. And until some numbers come out that explain the Vikings farming in Greenland, we can’t believe any of it. Even the Lamb reconstruction (pre-Mann) only puts MWP warming at about what they claim warming today is. Actually, today’s warming – once the allow for UHI and rural-urban bias – may actually be real. But to think that today no one can farm in Greenland even though the warming is the same – does that make sense? Of course not. So, what levels should we see in the MWP? At least add that 0.8C that the divergence is showing. But is that enough? I don’t think so.

    Don’t forget that if today’s divergence exists, when else in history did it “exist”? I put that in quotes, because we don’t have instruments to compare the MWP years to (nor the the LIA, really). But if the current indicated tree-ring>temps (which are ignored) actually ARE correct, then the MWP values of 0.5C higher than present (Mann 2003) or 0.4C higher (Crowley & Lowery) are added onto the currently accepted levels, the MWP is as high or higher than the late 1990s. But is that all there is to it? If the linearity of tree-rings>temps doesn’t hold, then what values are real? We simpoly can’t know that, because no on has gone out looking to see what the real relationship between tree-rings and temps is.

    Then add to that the fact tree-rings were originally seen as proxies for – not temps, but – precipitation, and all bets are off. Tree-rings can’t be proxies for both precip and temps, because even if they can tell what the weighting is for one vs the other in the instrument period, there is no reasonable assurance that the weighting holds for past eras.

    So, take away the tree-rings, and what is left? Ice cores that were calibrated against the tree-rings in the first place? That won’t work. Are we left with anything at all to use as proxies? And if so, what level of precision do we end up with? I can’t see anyone claiming any values in the 0.1C range. Not with a straight face. The uncertainty levels would be off the charts.

    It is all a big pile of “crap” science, to use The Team’s own terminology. We currently do not know ANYTHING reliable about past temps. How will we ever know? If farmers move to Greenland, then we know how warm it was in the MWP. Until then, it is all a bunch of ????s…

  10. Jeff Id said


    I agree with your points.

    One of the big problems in explaining what is wrong with paleowhakology is that there are so many problems. People are usually shocked into thinking that I (or someone else making the points) is acting as an advocate rather than a realist. I’ve made the points about the math so strongly here that McIntyre has written here that the data is the big problem. In reality, it is both but the data is worse as he said. The problem though is caused by high noise and multivariate calibrations followed by averaging.

    We don’t know if how much temperature signal is in the the proxy data. I attempted an estimate of the signal in the data once and came up with under 5% signal. I’m not convinced that my method was the most valid but I gave it a legitimate attempt. Even if I’m way off (which I don’t believe), there isn’t much signal there.

    The noisier the data, the flatter the handle.

  11. AMac said

    > The noisier the data, the flatter the handle.

    Yep. This makes so much sense, once one has gotten a first-hand look at some of the data, played with them a bit, and then thought about the subject. Even if one has limited advanced maths skills (looks in mirror).

    In the literature, the paleo experts avoid grasping this nettle. When they have ventured onto blogs — Mainstream-friendly ones or ones like tAV — they typically ignore it, or fume and sputter.

    “To see what is in front of one’s nose needs a constant struggle.” Was Orwell commenting on climate science?

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