Wednesday, May 9, 2012


date: Sun, 7 Apr 2002 17:04:20 -0400
from: "" <>
subject: RE: Re: Briffa & Osborn piece
to: "" <>

Hi Keith, Your reply arrived while I was in Mike's office. I decided not to read it until
after I got home, figuring that it was best to let sleeping dogs lie while in the den of
the lion. In any case, you were really far more reserved than I expected. That's good. I am
going to send out a comment to everyone tomorrow to clarify a bit on the "scaling" issue
and history of it. The irony is that Mike and others (e.g. Crowley, Hughes) saw exactly
what was published before I even submitted the paper and Mike thought that it was very
informative at the time. So, all of this complaining about the scaling (perhaps somewhat
legitimate, but a bit more complicated that Mike makes it out to be) is really odd. I am
always willing to listen to sound criticisms of my work and would have at least looked at
the scaling issue a bit more thoroughly had I received the criticism that I am getting now.
In any case, from what Tim has told me, Mike's argument about the tropics being responsible
for the reduced multi-centennial amplitude in MBH does not hold up using his actual
estimates from the extratropics. I don't know what you plan to do with this insight, but
Mike will not be pleased if it is advertised. Another box has arrived and I have told Nic
to send you an updated inventory list. Cheers, Ed Original Message: ----------------- From:
Keith Briffa Date: Fri, 05 Apr 2002 17:17:55 +0100 To:,,,,,,,, Subject: Re: Briffa & Osborn piece
Dear Mike, (and interested colleagues)
Given the list of people to whom you have chosen to circulate your message(s), we thought
we should make a short, somewhat formal, response here. I am happy to reserve my informal
response until we are face to face! We did not respond earlier because we had more pressing
tasks to deal with. This is not the place to go into a long or over-detailed response to
all of your comments but a few brief remarks might help to clear up a couple of
You consider our commentary on Ed and Jan's paper
"more flawed than even the paper itself"
on the basis that scaling the relationship between full Northern Hemisphere and
extratropical Northern Hemisphere is *much* more problematic than even any of the seasonal
issues we discuss. In fact we did not do this. The curve labelled Mann99 in our figure
was, in fact, based on the average of only the land areas, north of 20 degrees N, extracted
from your spatially-resolved reconstructions. We then scaled it by calibration against the
instrumental annual temperatures from the same region. This is, just as you stress in your
comments on the Esper et al. paper, what should have been done. We think that this single
point addresses virtually of all your concerns. We can, of course, argue about what this
means for the pre-1400 part of your reconstruction, when only 1 EOF was reconstructed, but
the essential message is that we did our best to exclude the tropics (and the oceans too!)
from your series so that it could more readily be compared with the other records.
The fact that we have used only the extra-tropical land from your data is not clear from
the text, so we can see why you may not have appreciated this, but we think you will
concede that this fact negates much of what you say and that we acted "more correctly" than
you realised. Blame *Science* for being so mean with their space allocation if you want!
Remember that this was an unrefereed piece and we felt justified in concentrating on one
issue; that of the importance of the method of scaling and its effect on apparent
"absolute" reconstruction levels. In our draft, we went on to say that this was crucial
for issues of simple model sensitivity studies and climate detection, citing the work of
Tom Crowley and Myles Allen, but this fell foul of the editor's knife.
You also express concerns about the calibration of Esper et al. (e.g., you say "if the
authors had instead used the actual (unsmoothed) instrumental record for the extratropical
northern hemisphere to scale their record, their reconstruction would be much closer to
This point is wholly consistent with our discussion in the perspective piece, and indeed we
show that in absolute terms the records are closer when Esper et al. is calibrated using
unsmoothed data but since the variance is also reduced, the significance of the
differences may be just as high.
Finally, we have to say that we do not feel constrained in what we say to the media or
write in the scientific or popular press, by what the sceptics will say or do with our
results. We can only strive to do our best and address the issues honestly. Some
"sceptics" have their own dishonest agenda - we have no doubt of that. If you believe that
I, or Tim, have any other objective but to be open and honest about the uncertainties in
the climate change debate, then I am disappointed in you also.
Best regards
Keith (and Tim)
At 12:39 PM 3/22/02 -0500, Michael E. Mann wrote:

Keith and Tim,
Sadly, your piece on the Esper et al paper is more flawed than even the paper itself.
Ed, the AP release that appeared in the papers was even worse. Apparently you allowed
yourself to be quoted saying things that are inconsistent with what you told me you had
You three all should have known better. Keith and Tim: Arguing you can scale the
relationship between full Northern Hemisphere and extratropical Northern Hemisphere is
*much* more problematic than even any of the seasonal issues you discuss, and this isn't
even touched on in your piece. The evidence of course continues to mount (e.g., Hendy et
al, Science, a couple weeks ago) that the tropical SST in the past centuries varied far
more less in past centuries. Hendy et al specifically point out that there is little
evidence of an LIA in the tropics in the data. The internal inconsistency here is
remarkably ironic. The tropics play a very important part in our reconstruction, with
half of the surface temperature estimate coming from latitudes below 30N. You know this,
and in my opinion you have knowingly misrepresented our work in your piece.
This will be all be straightened out in due course. In the meantime, there is a lot of
damage control that needs to be done and, in my opinion, you've done a disservice to the
honest discussions we had all had in the past, because you've misrepresented the
evidence. Many of us are very concerned with how Science dropped the ball as far as the
review process on this paper was concerned. This never should have been published in
Science, for the reason's I outlined before (and have attached for those of you who
haven't seen them). I have to wonder why the functioning of the review process broke
down so overtly here,
_______________________________________________________ ________________
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
[1] ml

Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.

Phone: +44-1603-593909
Fax: +44-1603-507784
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