Thursday, June 7, 2012


cc: "raymond s.bradley" <>,, "Phil Jones" <>, Scott Rutherford <>
date: Thu, 30 Oct 2003 12:11:21 -0500
from: "Michael E. Mann" <>
subject: Re: Can you believe it???
to: Keith Briffa <>, Tim Osborn <>

Thanks Keith,
I really appreciate your help.
I'm happy for us to try to soften the tone, and will look forward to your suggested
changes, etc. in this regard.
I'm about 99% sure, at this point, that my facts are right though--look forward to hearing
what you think I've reading through it--its dense, takes some effort to figure out what
they eliminated. But they appear to have eliminated *just* the right series.. It really was
a censoring of data as far as I can tell, key data...
talk to you later,
p.s. as for the target audience/date--I'll defer to you guys. I think, from Tim's comments,
this has to go out quickly. We've got to nip this in the bud before it gets any more play.
So I'm thinking, tomorrow at the latest.
Target audience--i think the idea is the same huge email distribution/listserv that they
sent their disinformation out to in the first place.
At 04:50 PM 10/30/2003 +0000, Keith Briffa wrote:

Mike and others
I am sorry but been in a meeting all day - my first impression of reading the text is to
caution against releasing this statement without more discussion. Do not be bounced into
saying stuff you are not sure of , and using emotive language that smacks of too
emotional a response . I am staying a while to read and comment in detail - and will try
to fax something. Have to go soon because of daughter and need to write 2 PhD proposals
tonight . Please clarify if there is a deadline that you are working too and what target
is this piece aimed at.?
At 09:35 AM 10/30/03 -0500, Michael E. Mann wrote:

I'm right, aren't I????
At 02:13 PM 10/30/2003 +0000, Tim Osborn wrote:

At 14:02 30/10/2003, you wrote:

Guys, can you take a look at this.
I think that everything I say here is true! But we've got to be sure.
There are more technical things they did wrong that I want to add, but this is the
critical bit--what do you think. Comments? Thanks...
The recent paper by McIntyre and McKitrick (Energy and Environment, 14, 751-771) claims
to be an "audit" of the analysis of Mann, Bradley and Hughes (1998) or "MBH98". An
audit involves a careful examination, using the same data and following the exact
procedures used in the report or study being audited. McIntyre and McKitrick ("MM")
have done no such thing, having used neither the data nor the procedures of MBH98. Their
analysis is notable only in how deeply they have misrepresented the data, methods, and
results of MBH98. Journals that receive critical comments on a previously published
papers always provide the authors who are being criticized an opportunity to review the
study prior to publication, and offer them the chance to respond. This is standard
operating procedure in any legitimate peer-reviewed scientific journal. Mann and
colleagues were never given this opportunity, nor were any other leading paleoclimate
scientists that we're familiar with. It is unfortunate that the profound errors, and
false and misleading statements, and entirely spurious results provided in the McIntyre
and McKitrick article were ever allowed to see the light of day by those would have been
able to detect them. . We suspect the extremely checkered history of "Energy and
Environment" has some role to play in this. The authors should retract their article
immediately, and issue a public apology to the climate research community for the
injustice they have done in publishing and promoting this deeply deceptive and flawed
Not only were critical errors made in their analysis that render it thoroughly invalid,
but there appear to have been several strikingly subjective decisions made to remove key
indicators of the original MBH98 network prior to AD 1600, with a dramatic impact on the
resulting reconstruction. It is precisely the over which the numerous indicators were
removed (pre 1600 period) during which MM reconstruct anomalous warmth that is in sharp
opposition to the cold conditions observed in MBH98 and nearly all other independent
published estimates that we know of.
While the authors dutifully cite the small inconsistency between the number of proxy
indicators reported by, and found in the public data archive, of Mann et al back in time
(there indeed appear to have been some minor typos in the MBH98 paper), it is odd that
they do not cite the number of indicators in their putative version of the Mann et al
network based on the independent collection of data, back time. The reader is literally
left to do a huge amount of detective work, based on the tables in their pages 20-23, to
determine just what data have been eliminated from the original Mann et al network. It
seems odd, indeed, that their "substitutions" of other versions (or in some case, only
apparent, and not actual, versions) of proxy data series for those in the original Mann
et al (1998) network has the selective effect of deleting key proxy indicators that
contribute dramatic cooling during the 16th century, when the MM reconstruction shows an
anomalous warming departure from the Mann et al (1998) and all other published Northern
Hemisphere temperature reconstructions.
Here are some blatant examples:
1) The authors (see their Figure 4) substitute a younger version of one of the Jacoby et
al Northern Treeline series for the older version used by MBH98. This substitution has
effect of removing a predictor of 15th century cooling [Incidentally, MM make much of
the tendency for some tree ring series, such as this one, to show an apparent cooling
over the past couple decades. Scientists with expertise in dendroclimatology know that
this behavior represents a decrease in the sensitivity to temperature in recent decades
that likely is related to conditions other than temperature which are limiting tree
2) The authors eliminate, without any justification, the entire dataset of 70 Western
North American (WNA) tree-ring series available between 1400 and 1600 (this dataset is
represented, by MBH98, in terms of a smaller number of representative Principal
Component time series). The leading pattern of variance in this data set exhibits
conditions from 1400-1800 that are dramatically colder than the mid and late 20th
century, and a very prominent cooling in the 15th century in particular. The authors
eliminated this entire dataset because they claimed that the underlying data was not
available in the public domain.
In point of fact, not only were the individual WNA data all available on the public ftp
site provided by Mann and colleagues:
[1], but they were also
available, despite the claims to the contrary by MM, on NOAA's website as well:
The deletion of this critical (see Mann et al, 1999) dataset appears to one of the more
important censorings performed by MM that allows them to achieve their spurious result
of apparent 15th-16th century warmth.
We have not, as yet, finished determining just how many important indicators were subtly
censored from the MBH98 dataset by the various subjective substitutions described on
pages 20-23. However, given the relatively small number of indicators available between
1400-1500 in the MBH98 network (22-24) and their elimination of some of the more
critical ones, it would appear that this subjective censoring of data, alone, explains
the spurious, misleading, and deceptive result achieved by the authors.
Incidentally, MBH98 go to great depths to perform careful cross-validation experiments
as a function of increasing sparseness of the candidate predictors back in time, to
demonstrate statistically significant reconstructive skill even for their earlier
(1400-1450) reconstruction interval. MM describe no cross-validation experiments. We
wonder what the verification resolved variance is for their reconstruction based on
their 1400-1450 available network, during the independent latter 19th century period?
There are numerous other serious problems that would render the MM analysis completely
invalid, even in the absence of the serious issue raised above, and these are detailed
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
e-mail: Phone: (434) 924-7770 FAX: (434) 982-2137

Dr Timothy J Osborn
Climatic Research Unit
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, UK
phone: +44 1603 592089
fax: +44 1603 507784
web: [4]
sunclock: [5]

Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
e-mail: Phone: (434) 924-7770 FAX: (434) 982-2137

Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.
Phone: +44-1603-593909
Fax: +44-1603-507784

Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
e-mail: Phone: (434) 924-7770 FAX: (434) 982-2137

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