Bishop Hill Writes:

Email 2383 contains further evidence that everyone in the world of paleoclimate knew the Hockey Stick was a duffer.

From: Tim Barnett [[2]mailto:XXXXXXXXXXX@ucsd.edu] Sent: 11 October 2004 16:42 To: Gabi Hegerl; Klaus Hasselmann Cc: Prof.Dr. Hans von Storch; Myles Allen; francis; Reiner Schnur; Phil Jones; Tom Crowley; Nathan Gillett; David Karoly; Jesse Kenyon; christopher.d.miller@noaa.gov; Pennell, William T; Tett, Simon; Ben Santer; Karl Taylor; Stott, Peter; Bamzai, Anjuli Subject: Re: spring meeting not to be a trouble maker but……if we are going to really get into the paleo stuff, maybe someone(s) ought to have another look at Mann’s paper. His statistics were suspect as i remember. for instance, i seem to remember he used, say, 4 EOFs as predictors. But he prescreened them and threw one away because it was not useful. then made a model with the remaining three, ignoring the fact he had originally considered 4 predictors. He never added an artifical skill measure to account for this but based significance on 3 predictors. Might not make any difference. My memory is probably faulty on these issues, but to be completely even handed we ought to be sure we agree with his procedures. best, tim

It’s interesting how much evidence there is now that the Hockey Stick was known to be a problem. Perhaps readers can help collate a list of emails making this point.

NAS panel review of hockeysticks prompted by McIntyre and McKitrick.

#1104 -Heinz Wanner – on reporting his NAS panel critique of Mann to the media.

I just refused to give an exclusive interview to SPIEGEL because I will not cause damage for climate science.

#1656 Douglas Maraun – on how to react to skeptics.

How should we deal with flaws inside the climate community? I think, that “our” reaction on the errors found in Mike Mann’s work were not especially honest.

#3234 Richard Alley

Taking the recent instrumental record and the tree-ring record and joining them yields a dramatic picture, with rather high confidence that recent times are anomalously warm. Taking strictly the tree-ring record and omitting the instrumental record yields a less-dramatic picture and a lower confidence that the recent temperatures are anomalous.

Paleoclimate and hide the decline

#0300

Bo Christiansen – On Hockey stick reconstructions

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.

Ed Cook #3253

the results of this study will show that we can probably say a fair bit about <100 year extra-tropical NH temperature variability (at least as far as we believe the proxy estimates), but honestly know fuck-all about what the >100 year variability was like with any certainty (i.e. we know with certainty that we know fuck-all).

#4133 Johnathan Overpeck – IPCC review.

what Mike Mann continually fails to understand, and no amount of references will solve, is that there is practically no reliable tropical data for most of the time period, and without knowing the tropical sensitivity, we have no way of knowing how cold (or warm)the globe actually got.

[and later]

Unsatisfying, perhaps, since people will want to know whether 1200 AD was warmer than today, but if the data doesn’t exist, the question can’t yet be answered. A good topic for needed future work.

Rob Wilson – 1583

The palaeo-world has become a much more complex place in the last 10 years and with all the different calibration methods, data processing methods, proxy interpretations – any method that incorporates all forms of uncertainty and error will undoubtedly result in reconstructions with wider error bars than we currently have. These many be more honest, but may not be too helpful for model comparison attribution studies. We need to be careful with the wording I think.

#3234 Richard Alley – on NAS panel and divergence

records, or some other records such as Rosanne’s new ones, show “divergence”, then I believe it casts doubt on the use of joined tree-ring/instrumental records, and I don’t believe that I have yet heard why this interpretation is wrong.

#4758 Tim Osborne – Criticizing other people for doing the same thing

Because how can we be critical of Crowley for throwing out 40-years in the middle of his calibration, when we’re throwing out all post-1960 data ‘cos the MXD has a non-temperature signal in it, and also all pre-1881 or pre-1871 data ‘cos the temperature data may have a non-temperature signal in it! If we write the Holocene forum article then we’ll have to be critical or our paper as well as Crowley’s!

#0497 – Phil Jones UEA – Scientists don’t know the magnitude of past warming.

Even though the tree-ring chronologies used have robust rbar statistics for the whole 1000 years ( ie they lose nothing because core numbers stay high throughout), they have lost low frequency because of standardization. We’ve all tried with RCS/very stiff splines/hardly any detrending to keep this to a minimum, but until we know it is minimal it is still worth mentioning.

#0886 Jan Esper on his own reconstruction – also hidden decline

And the curve will also show that the IPCC curve needs to be improved according to missing long-term declining trends/signals, which were removed (by dendrochronologists!) before Mann merged the local records together.

Tiim Osborne 4007

Also we have applied a completely artificial adjustment to the data after 1960, so they look closer to observed temperatures than the tree-ring data actually were

Tim Osborne #2347

Also, we set all post-1960 values to missing in the MXD data set (due to decline), and the method will infill these, estimating them from the real temperatures – another way of “correcting” for the decline, though may be not defensible!

#3234 Richard Alley

Unless the “divergence problem” can be confidently ascribed to some cause that was not active a millennium ago, then the comparison between tree rings from a millennium ago and instrumental records from the last decades does not seem to be justified, and the confidence level in the anomalous nature of the recent warmth is lowered.

I think the best way to sum up all of this is a quote from a guest post at tAV and DieKlimazweibel by Bo Christiansen:

Where does all this lead us? It is very likely that the NH mean temperature has shown much larger past variability than caught by previous reconstructions. We cannot from these reconstructions conclude that the previous 50-year period has been unique in the context of the last 500-1000 years.

Of course we all know that the IPCC reports differently.

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