cc: Gabi Hegerl <hegerlatXYZxyze.edu>, tom crowley <tomatXYZxyzan.tamu.edu>, mhughes@ltrr.arizona.edu, "raymond s.bradley" <rbradleyatXYZxyz.umass.edu>, Keith Briffa <k.briffaatXYZxyz.ac.uk>, Jonathan Overpeck <jtoatXYZxyzrizona.edu>, Stefan Rahmstorf <rahmstorfatXYZxyz-potsdam.de>, Steve Schneider <shsatXYZxyznford.edu>, peter.stott@metoffice.com, Gavin Schmidt <gavinatXYZxyzs.giss.nasa.gov>, mannatXYZxyztiproxy.evsc.virginia.edu

date: Wed, 29 Oct 2003 13:05:19 -0500

from: "Michael E. Mann" <mannatXYZxyzginia.edu>

subject: Fwd: STOP THE PRESS!

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Date: Tue, 28 Oct 2003 21:43:33 -0500

To: "Richard Kerr" <rkerratXYZxyzs.org>, Andy Revkin <anrevkatXYZxyzimes.com>,

David Appell <appellatXYZxyzw.org>, Stephen H Schneider <shsatXYZxyznford.edu>,

Annie_Petsonk@environmentaldefense.org,

Mike MacCracken <mmaccracatXYZxyzcast.net>,

Michael Oppenheimer <omichaelatXYZxyznceton.EDU>,

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mhughes@ltrr.arizona.edu, Jonathan Overpeck <jtoatXYZxyzrizona.edu>,

Phil Jones <p.jonesatXYZxyz.ac.uk>, Scott Rutherford <srutherfordatXYZxyz.edu>,

Gabi Hegerl <hegerlatXYZxyze.edu>, tom crowley <tomatXYZxyzan.tamu.edu>,

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thompson.4@osu.edu, thompson.3atXYZxyz.edu

From: "Michael E. Mann" <mannatXYZxyzginia.edu>

Subject: STOP THE PRESS!

Cc: mannatXYZxyzginia.edu

Dear Friends and Colleagues,

I've got a story with a very happy ending to tell. I't will take a bit of patience to

get through the details of the story, but I think its worth it.

By the way, please keep this information confidential for about the next day or so.

OK, well its about 48 hours since I first had the chance to review the E&E paper by M&M.

Haven't had a lot of sleep, but I have had a lot of coffee, and my wife Lorraine has

been kind enough to allow me to stay perpetually glued to the terminal. So what has this

effort produced?

Well, upon first looking at what the authors had done, I realized that they had used

the wrong CRU surface temperature dataset (post 1995 version) to calculate the standard

deviations for use in un-normalizing the Mann et al (1998) EOF patterns. Their

normalization factors were based on Phil's older dataset. The clues to them should have

been that a) our data set goes back to 1854 and theirs only back to 1856 and (b) why are

4 of the 1082 Mann et al (1998) gridpoints missing?? [its because the reference periods

are different in the two datasets, which leads to a different spatial pattern of missing

values]. So they had used the wrong temperature standard deviations to un-normalize our

EOFs in the process of forming the surface temperature reconstruction. And I thought to

myself, hmm--this could lead to some minor problems, but I don't see how they get this

divergence from the Mann et al (1998) estimate that increases so much back in time, and

becomes huge before 1500 or so. That can't be it, can it?

Then I uncovered that they had used standard deviations of the raw gridpoint temperature

series to un-normalize the EOFs, while we had normalized the data by the detrended

standard deviations. Either convention can be justified, but you can't mix and

match--which is what they effectively did by adopting our EOFs and PCs, and using their

standard deviations. And I thought, hmm--this could certainly lead to an artificial

inflation of the variance in the reconstruction in general, and this could give an

interesting spatial pattern of bias as well (which might have an interesting influence

on the areally-weighted hemispheric mean). But I thought, hmm, this can't really lead to

that tremendous divergence before 1500 that the authors find. I was still scratching my

head a bit at this point.

Then I read about the various transcription errors, values being shifted, etc. that the

authors describe as existing in the dataset. And I thought, hmm, that sounds like an

excel spread sheet problem, not a problem w/ the MBH98 proxy data set. It started to

occur to me at this point that there might be some problems w/ the excel spreadsheet

data that my colleague Scott Rutherford had kindly provided the authors at their

request. But these problems sounded pretty minor from the authors' description, and the

authors described a procedure to try to fix any obvious transcription errors, shifted

cell values, etc. So I thought, hmm, they might not have fixed things perfectly, and

that could also lead to some problems. But I still don't see how they get that huge

divergence back in time from this sort of error...

Still scratching my head at this point...Then finally this afternoon, some clues. After

looking at their on-line description one more time, I became disturbed at something I

read. The data matrix they're using has 112 columns! Well that can't be right! That's

can't constitute the Mann et al (1998) dataset. There are considerably more than that

number of independent proxy indicators necessary to reproduce the stepwise Mann et al

reconstruction. Something is amiss!

Well, 112 is the number of proxy indicators used back to 1820. But some of these

indicators are principal components of regional sub-networks (e.g. the Western U.S.

ITRDB tree-ring data) to make the dataset more managable in size, and those principal

components (PCs) are unique to the time interval analyzed. So there is some set of PC

series for the 1820-1980 period. Farther back in time, say, back to 1650 there are fewer

data series the regional sub-networks. So we recalculate a completely different EOF/PC

basis set for that period, and that constitutes an additional, unique set of proxy

indicators that are appropriate for a reconstruction of the 1650-1980 period. PC #1 from

one interval is not equivalent to PC#1 from a different interval. This turns out to be

the essential detail. A reconstruction back to 1820 calibrated against the 20th

century needs to make use of the unique set of proxy PCs available for the 1820-1980

period. A reconstruction back to 1650 calibrated against the 20th century needs to make

use of the independent (smaller) set of PC series available for the 1650-1980 period,

and so on, back to 1400.

So there have to be significantly more than 112 series available to perform the

iterative,stepwise reconstruction approach of Mann et al (1998), because each sub

interval actually has a unique set of PC series representations of various proxy

sub-networks. Then it started to hit me. The PC#1 series calculated for networks of

similar size (say, the network available back to 1820 and that available back to 1750)

should be similar. But as the sub-network gets sparser back in time, the PC#1 series

will resemble less and less the PC#1 series of the denser networks available at later

times. PC#1 of the western ITRDB tree-ring calculated for the 1400-1980 period will

bear almost no resemblance to the PC#1 series of the western N.Amer ITRDB data

calculated for the 1820-1980 period during their interval (1820-1980) of mutual overlap.

Then it really hit me. What--just what--if the proxy data had been pigeonholed into a

112 column matrix by the following (completely inappropriate!) procedure: What if it had

been decided that there would only be 1 column for "PC #1 of the Western ITRDB tree ring

data", even though that PC reflects something completely different over each

sub-interval. Well, that can't be done in a reasonable way. But it can be done in an

*unreasonable* way: by successively overprinting the data in that column as one stores

the PCs from later and later intervals. So a given column would reflect PC#1 of the

1400-1980 data from 1400-1450, PC#1 of the 1450-1980 from 1450-1500, PC#1 of the

1500-1980 data for 1500-1650, PC#1 of the 1650-1980 data for 1650-1750, etc. and so on.

In this process, the information necessary to calibrate the early PCs would be

obliterated with each successive overprint. The resulting 'series' corresponding to

that column of the data matrix, an amalgam of increasingly unrelated information down

the column, would be completely useless for calibration of the earlier data. A

reconstruction back to AD 1400 would be reconstructing the PC#1 of the 1400-1450

interval based on calibration against the almost entirely unrelated PC#1 of the

1820-1980 interval. The reconstruction of the earliest centuries would be based on a

completely spurious calibration of an unrelated PC of a much later proxy sub network.

And I thought, gee, what if Scott (sorry Scott), had *happened* to do this in preparing

the excel file that the authors used. Well it would mean that, progressively in earlier

centuries, one would be reconstructing an apple, based on calibration against an

orange. It would yield completely meaningless results more than a few centuries ago. And

then came the true epiphany--ahhh, this could lead to the kind of result the authors

produced. In fact, it seemed to me that this would almost *insure* the result that the

authors get--an increasing divergence back in time, and total nonsense prior to 1500 or

so. At this point, I knew that's what Scott must have done. But I had to confirm.

I simply had to contact Scott, and ask him: Scott, when you prepared that excel file for

these guys, you don't suppose by any chance that you might have....

And, well, I think you know the answer.

So the proxy data back to AD 1820 used by the authors may by-in-large be correct (aside

from the apparent transcription/cell shift errors which they purport to have caught, and

fixed, anyway). The data become progressively corrupted in earlier centuries. By the

time one goes back to AD 1400, the 1400-1980 data series are, in many cases, entirely

meaningless combinations of early and late information, and have no relation to the

actual proxy series used by Mann et al (1998).

And so, the authors results are wrong/meaningless/useless. The mistake made insures,

especially, that the estimates during the 15th and 16th centuries are entirely spurious.

So whose fault is this? Well, the full, raw ascii proxy data set has been available on

our anonymous ftp site [1]ftp://holocene.evsc.virginia.edu/pub/MBH98/

and the authors were informed of this in email correspondence. But they specifically

requested that the data be provided to them in excel format. And Scott prepared it for

them in that format, in good faith--but overlooked the fact that all of the required

information couldn't possibly be fit into a 112 column format. So the file Scott

produced was a complete corruption of the actual Mann et al proxy data set, and

essentially useless, transcription errors, etc. aside. The authors had full access to

the uncorrupted data set. We therefore take no reasonability for their use of corrupted

data.

One would have thought that the authors might have tried to reconcile their completely

inconsistent result prior to publication. One might have thought that it would at least

occur to them as odd that the Mann et al (1998) reconstruction is remarkably similar to

entirely independent estimates, for example, by Crowley and Lowery (2000). Could both

have made the same supposed mistake, even though the data and method are entirely

unrelated. Or might M&M have made a mistake? Just possibly, perhaps???

Of course, a legitimate peer-review process would have caught this problem. In fact, in

about 48 hours if I (or probably, many of my colleagues) had been given the opportunity

to review the paper. But that isn't quite the way things work at "E&E" I guess. I guess

there may just be some corruption of scientific objectivity when a journal editor seems

more interested in politics than science.

The long and short of this. I think it is morally incumbent upon E&E to publish a full

retraction of the M&M article immediately. Its unlikely that they'll do this, but its

reasonable to assert that it would be irresponsible for them not to if the issue arises.

I think that's the end of the story. Please, again, keep this information under wraps

for next day or two. Then, by all means, feel free to disseminate this information as

widely as you like...

Mike

______________________________________________________________

Professor Michael E. Mann

Department of Environmental Sciences, Clark Hall

University of Virginia

Charlottesville, VA 22903

_______________________________________________________________________

e-mail: mannatXYZxyzginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137

[2]http://www.evsc.virginia.edu/faculty/people/mann.shtml

______________________________________________________________

Professor Michael E. Mann

Department of Environmental Sciences, Clark Hall

University of Virginia

Charlottesville, VA 22903

_______________________________________________________________________

e-mail: mannatXYZxyzginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137

[3]http://www.evsc.virginia.edu/faculty/people/mann.shtml

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