Climategate 3.0: Mann to Revkin — ‘McIntyre and McKitrick paper is pure scientific fraud’

Unlike the notion of estimating global temps 1,000 years ago to within tenths of a degree by analyzing tree rings?

The e-mail is below.

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Date: Fri, 04 Feb 2005 15:52:53 -0500
To: Andy Revkin
From: “Michael E. Mann”
Subject: Re: FW: “hockey stock” methodology misleading
Hi Andy,
The McIntyre and McKitrick paper is pure scientific fraud. I think you’ll
find this
with.
Please see the RealClimate response:
[1]http://www.realclimate.org/index.php?p=111
and also:
[2]http://www.realclimate.org/index.php?p=114
The Moberg et al paper is at least real science. But there are some real
problems with
it (you’ll want to followup w/ people like Phil Jones for a 2nd opinion).
While the paper actually reinforces the main conclusion of previous studies
(it also
finds the late 20th century to be the warmest period of the past two
millennia), it
challenges various reconstructions
using tree-ring information (which includes us, but several others such as
Jones et al,
Crowley, etc). I’m pretty sure, by the way, that a very similar version of
the paper was
rejected previously by Science. A number of us are therefore very surprised
that Nature
is publishing it, given a number of serious problems:
Their method for combining frequencies is problematic and untested:
A. they only use a handful of records, so there is a potentially large
sampling bias.
B. worse, they use different records for high-frequencies and lowfrequencies,
so the
bias isn’t even the same–the reconstruction is apples and oranges.
C. The wavelet method is problematic. We have found in our own work that
you cannot
simply combine the content in different at like frequencies, because
different proxies
have different signal vs. noise characteristics at different frequencies–
for some
records, there century-scale variability is likely to be pure noise. They
end up
therfore weighting noise as much as signal. For some of the records used,
there are real
age model problems. The timescale isn’t known to better than +/- a couple
hundred years
in several cases. So when they average these records together, the centuryscale
variability is likely to be nonsense.
D. They didn’t do statistical verification. This is absolutely essential
for such
reconstructions (see e.g. the recent Cook et al and Luterbacher et al
papers in
Science). They should have validated their reconstruction against longinstrumental
records, as we and many others have. Without having done so, there is no
reason to
believe the reconstruction has any reliability. This is a major problem w/
the paper. It
is complicated by the fact that they don’t produce a pattern, but just a
hemispheric
mean–that makes it difficult to do a long-term verification. But they
don’t attempt any
sort of verification at all! There are some decades known to be warm from
the available
instrumental records (1730s, some in the 16th century) which the Moberg
reconstruction
completely misses–the reconstruction gives the impression that all years
are cold
between 1500 and 1750. The reconstruction would almost certainly fail
cross-validation
against long instrumental records. If so, it is an unreliable estimate of
past changes.
We’re surprised the Nature Reviewers didn’t catch this.
E. They also didn’t validate their method against a model (where I believe
it would
likely fail). We have done so w/ our own “hybrid frequency-domain” method
that combines
information separately at low and high-frequencies, but taking into account
the problem
mentioned above. This is described in:
Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R.,
Hughes, M.K.,
Jones, P.D., [3]Proxy-based Northern Hemisphere Surface Temperature
Reconstructions:
Sensitivity to Methodology, Predictor Network, Target Season and Target
Domain, Journal
of Climate, in press (2005).
In work that is provisionally accepted in “Journal of Climate” (draft
attached), we show
that our method gives the correct history using noisy “pseudoproxy” records
derived from
a climate model simulation with large past changes in radiative forcing.
Moberg et al
have not tested their method in such a manner.
F. They argue selectively for favorable comparison w/ other work:
(1) Esper et al: when authors rescaled the reconstruction using the full
instrumental
record (Cook et al, 2004), they found it to be far more similar to Mann et
al, Crowley
and Lowery, Jones et al, and the roughly dozen or so other empirical and
model estimates
consistent w/ it. Several studies, moreover [see e.g.: Shindell, D.T.,
Schmidt, G.A.,
Mann, M.E., Faluvegi, G., [4]Dynamic winter climate response to large
tropical volcanic
eruptions since 1600, Journal of Geophysical Research, 109, D05104, doi:
10.1029/2003JD004151, 2004.] show that extratropical, land-only summer
temperatures,
which Esper et al emphasises, are likely to biased towards greater
variability–so its
an apples and oranges comparison anyway.
(2) von Storch et al: There are some well known problems here: (a) their
forcing is way
too large (Foukal at al in Science a couple months back indicates maybe 5
times too
large), DKMI uses same model, more conventional forcings, and get half the
amplitude and
another paper submitted recently by the Belgium modeling group suggests
that some severe
spin-up/initialization problems give the large century-scale swings in the
model–these
are not reproducible.
(3) Boreholes: They argue that Boreholes are “physical measurements” but
many papers in
the published literature have detailed the various biases in using
continental ground
surface temperature to estimate past surface air temperature changes–
changing snow
cover gives rise to a potentially huge bias (see e.g. : Mann, M.E.,
Schmidt, G.A.,
[5]Ground vs. Surface Air Temperature Trends: Implications for Borehole
Surface
Temperature Reconstructions,Geophysical Research Letters, 30 (12), 1607,
doi:
10.1029/2003GL017170, 2003).
Methods that try to correct for this give smaller amplitude changes from
borehole
temperatures:
Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T.,
[6]Optimal
Surface Temperature Reconstructions using Terrestrial Borehole Data,
Journal of
Geophysical Research, 108 (D7), 4203, doi: 10.1029/2002JD002532, 2003]
[[7]Correction(Rutherford and Mann, 2004)]
Most reconstructions and model estimates still *sandwich” the Mann et al
reconstruction.
See e.g. figure 5 in: Jones, P.D., Mann, M.E., [8]Climate Over Past
Millennia, Reviews
of Geophysics, 42, RG2002, doi: 10.1029/2003RG000143, 2004.
Ironically, MM say our 15th century is too cold, while Moberg et al say its
too warm.
Hmmm….
To recap, I hope you don’t mention MM at all. It really doesn’t deserve any
additional
publicity. Moberg et al is more deserving of discussion, but, as outlined
above, there
are some real problems w/ it. I have reason to believe that Nature’s own
commentary by
Schiermeier will actually be somewhat critical of it.
I’m travelling and largely unavailable until monday. If you need to talk,
you can
possibly reach me at 434-227-6969 over the weekend.
I hope this is of some help. Literally got to run now…
mike
At 02:14 PM 2/4/2005, Andy Revkin wrote:
Hi all,
There is a fascinating paper coming in Nature next week (Moberg of
Stockholm Univ., et
al) that uses mix of sediment and tree ring data to get a new view of last
2,000 years.
Very warped hockeystick shaft (centuries-scale variability very large) but
still
pronounced ‘unusual’ 1990’s blade.
i’d like your reaction/thoughts for story i’ll write for next thursday’s
Times.
also, is there anything about the GRL paper forthcoming from Mc & Mc that
warrants a
response?
I can send you the Nature paper as pdf if you agree not to redistribute it
(you know the
embargo rules).
that ok?
thanks for getting in touch!
andy
______________________________________________________________
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
_______________________________________________________________________
e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137
[9]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: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137
[10]http://www.evsc.virginia.edu/faculty/people/mann.shtml