Sunday, June 3, 2012

4871.txt

date: Wed Feb 15 16:43:41 2006
from: Keith Briffa <k.briffaatXYZxyz.ac.uk>
subject: bullets
to: jtoatXYZxyzrizona.edu

Peck
do not think you will like what I say here , but I am going to give straight answers to
your questions.
First
The new draft says enough in the text now about "far-less-accurately dated" and
"low-resolution proxy records that can not be rigorously calibrated" in relation to this
paper (Moberg et al.) . It is not appropriate to single the one series out for specific
criticism in the summary . The use of the word "only" implies we do not believe it. Mike
Mann's suggestion begs a lot of questions about what constitutes "significantly warmer".
You need to have a Null Hypothesis to test . If you mean would the estimates in Moberg and
the other reconstructions (during medieval time) show significantly different means using a
t-test - then of course not , but this tells us nothing other than they are not likely
samples from totally different populations - an almost impossible test to pass given the
wide uncertainties on all reconstructions . Incidentally, we do not have formal
(calibration ) uncertainties for Moberg anyway (just boot-strapped uncertainty on the
average low-frequency curve).
I think the vagueness is necessary - "suggests slightly" and is appropriate.
I would not call out The results of Tim and my paper either. It is just an aside in the
Medieval box at present , perhaps with a Figure to accompany the original if you agree, but
without more text in the Chapter , which I do not consider appropriate, it should not be
highlighted as a bullet.
Second
Simply make "1000" "1300 years. " and delete "and unusually warm compared with the last
2000 years."
It is certainly NOT our job to be discussing attribution in the 20th century - this is
Chapter 9 - and we had no room (or any published material) to allow a discussion of
relative forcing contributions in earlier time. Therefore a vague statement about "perhaps
due to solar forcing" seems unjustified.
Third
I suggest this should be
Taken together , the sparse evidence of Southern Hemisphere temperatures prior to the
period of instrumental records indicates that overall warming has occurred during the last
350 years, but the even fewer longer regional records indicate earlier periods that are as
warm, or warmer than, 20th century means.
Fourth
fine , though perhaps "warmth" instead of "warming"?
and need to see EMIC text
Fifth
suggest delete
Sixth
suggest delete
Peck, you have to consider that since the TAR , there has been a lot of argument re "hockey
stick" and the real independence of the inputs to most subsequent analyses is minimal.
True, there have been many different techniques used to aggregate and scale data - but the
efficacy of these is still far from established. We should be careful not to push the
conclusions beyond what we can securely justify - and this is not much other than a
confirmation of the general conclusions of the TAR . We must resist being pushed to present
the results such that we will be accused of bias - hence no need to attack Moberg . Just
need to show the "most likely"course of temperatures over the last 1300 years - which we do
well I think. Strong confirmation of TAR is a good result, given that we discuss
uncertainty and base it on more data. Let us not try to over egg the pudding.
For what it worth , the above comments are my (honestly long considered) views - and I
would not be happy to go further . Of course this discussion now needs to go to the wider
Chapter authorship, but do not let Susan (or Mike) push you (us) beyond where we know is
right.

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

Phone: +44-1603-593909
Fax: +44-1603-507784
[1]http://www.cru.uea.ac.uk/cru/people/briffa/

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