Wednesday, May 9, 2012


date: Tue, 12 Jun 2007 17:39:02 -0400
from: Gabi Hegerl <>
subject: Re: Mitrie revision
to: Martin Juckes <>

Hi Martin et al.,

I have a few comments, that will probably come in two emails since I
need to run soon.
I am sorry they are a bit late, but I think its only words anyway, so I
hope its ok!


Abstract: I think what got to the reviewer was the maximum temperature
given by 3 significant
digits, I doubt we can know it that well - how about saying 0.25 K
(relative..) (and the residual
on 2 digits as well)?

Also, procedure (1) is, as far as I can tell, inverse regression of
regional records on hemispheric
mean (if I understand right) - this is nowhere fully spelled out, but
should be spelled out I think.
If you, for example, were to composite and then inverse regress the
composited average record,
you would get something identical to your (2) but with more variance
(and something much closer
to my paper and I think that works pretty well as well, but no need to
argue for that here at all, just
could we please be specific and say in abstract and once in main text
what we regress inversely? It
does make a difference?)

Introduction, 2nd para: The dominant change... you should cite eitehr
the entire IPCC report 2007 for that,
or chapter 2 of it - Mitchell et al is the attribution chapter and
doesnt really discuss forcing.

p. 2, left column, 2nd and 3rd column: I admit I am quite unhappy with
how this is phrased, and would
really love to have this changed. Reading it naively, I would conclude
that we cant yet estimate the
anthropgoenic contribution to the late 20th century warmth, while at the
same time being the first author
of the chapter saying we can and its dominant ...
How about replacing the first sentence of 2nd paragraph (However, there
with the following: The following two questions are essential for
understanding 20th century climate change
and thus credibly predicting future climate changes:...

Then, the beginning of the next paragraph:
Despite strong results from attribution studies, some uncertainty in the
answer to the first question remains....
I think this sounds less like we question 4AR conclusions...

p. 2, right column beginning of section 2: I think the attribution of
timeseries to reconstruction regions
is not correct everywhere. HCA2007, for example, is definitely NH
extratropics (N of 30N), and if you have
used "dark ages", its actually calibrated to land (does the series you
use go back to the 6th century?).
Also, I am nearly certain that JBB is a NH reconstruciton, and to my
knowledge is HPS extratropical land as
well (thats where the boreholes are). I think this paragraph needs a
sentence cautioning somewhere along the
line after temperature" : Note that some of the difference in variance
of timeseries can be attributed to different
areas resolved, the entire NH land and oceans varies weaker than, for
example, NH extratropical land only (if
all fails you can cite me but there's got tbe be a better citation).

p. 3, left column, discussion of JOnes reconstruction: It is also shown
that there are strong large scale coherencies in..proxy data... not
reproduced in climate model CONTROL simulations. (please add control, I
think thats what
they did, and internal variability will show less spatial coherence than
externally forced runs!)

more in the second email


and the borehole reconstruciton

For increasing the credibility of answers to both questions,
reconstructing and understanding climate
change over a longer time horizon, such as the past millennium, is
essential (Hegerl et al. 2007b)

Martin Juckes wrote:

>here is another update. I've incorporated Nanne's rewrite of the start of the
>new section 4, which shortens it by a couple of sentences.

Gabriele Hegerl
Division of Earth and Ocean Sciences,
Nicholas School for the Environment and Earth Sciences,
Box 90227
Duke University, Durham NC 27708
Ph: 919 684 6167, fax 684 5833


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