cc: Martin Juckes <m.n.juckes@rl.ac.uk>, anders@misu.su.se, Eduardo.Zorita@gkss.de, esper@wsl.ch, k.briffa@uea.ac.uk, m.allen1@physics.ox.ac.uk, weber@knmi.nl, t.osborn@uea.ac.uk
date: Wed, 13 Jun 2007 10:49:08 -0400
from: Gabi Hegerl <hegerl@duke.edu>
subject: Re: Mitrie revision
to: Gabi Hegerl <hegerl@duke.edu>

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Hi all,rest of comments (and sorry its a few comments, last time this 
came around I was solidly buried in IPCC
and couldnt look as closely at this as I should have, APOLOGIES! NOte 
that all changes I suggest are
really small fry, so I hope its not too late.
The two that are more important to me is to make sure we dont sound like 
we question 4AR conclusions (at least
not with me as author on it), and that it doesnt sound like all inverse
regression approaches have problems. The latter can be avoided if its a 
bit more specific about what particular
inverse regression appraoch was used!

Gabi



>
> 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). 


Later, some of the errors here are fixed, so just the first sentence 
needs some revisiting.

p. 3, right column, 3rd paragraph where you discuss the IPCC TAR 
conclusions: I think its essential to add that
the IPCC conclusions were not based on Mann et al alone - this is a 
misunderstanding that is propagated
and caused by the SPM showing only Mann's figure, but the chapter in the 
background show also Briffa and
Jones (fig 3.21 or so, although in low-pass resolution)
- this could be clarified by changing the sentence: MBH1998 and MBH1999 
have been.... since the latter was
cited in IPCC2001 though the IPCC conclusions were based on several 
reconstructions and weaker than those
of MBH1999.

Footnote 2 same page: I like the footnote about uncertainty, could we 
add to make it to: "...,which should include
expert assessment aof the robuistness of statistical methods employed 
AND REMAINING UNCERTAINTIES,
in addition to results of statistical tests (Manning etc)

p. 4, right column, boreholes last sentence - I think there is no 
question that the stationarity condition at the
beginning influences the initial stage or boreholes, so I wonder if "may 
influence" should change to "will influence"
- but up to you guys! (note that based on forcing, we do expect 
conditions before to have been warmer rather than
stationary...)

p. 5, end of 2nd paragraphL: Talking about the extended period of large 
scale warmth - should this also cite Osborn and Briffa, 2006?

p. 5, bottom of right column: According to my paper table 1, Esper et al 
correlates ~0.5 with Mann and 0.3 with Moberg on 20-yr smoothed data - 
"but has greater centennial variability" doesnt capture that entirely. 
should we add "but somewhat less on longer timescales? Just a 
suggestion, no strong feelings!

p. 6, bottom left colum: The variance matching thus represents a form of 
crossvalidation - I dont understand how
variance matching could be any calibration? Interannual variablity will 
be influenced by the trends... unless you
take them out prior to calculating the variance?

Section 2.7, when discussing that the oerlemanns lies midway between 
MBH1999 and HPS: Its not really a fair
comparison given that OER is global (?) and HPS NH land! So maybe add 
that information right there, saying
"However, HPS represents NH extratropical land, while OER represents 
global temperatures.
I also now think I remember that Mann and Jones discuss that it matters 
what a reconstruction represents (with land
and extratropics leading to higher variability eg)_

p. 7. right column: "The trend component 1000 to 1850 is, however, in 
all reconstructions larger than the trend
implied by the forcings" - I am not sure, is this shown in Nanne's 
paper? If yes, maybe cite? I dont find this, but
then I scale...

p.  9, top left: The borehole reconstructions, however, imply that there 
were colder temperatures  experienced in the 16th to 18th centuries - 
actually, most other recons impy that as well, so should we add this 
"The borehol reconstructions and many other reconstructions, however, 
imply..."?

p. 10, right column: .. this time using inverse regression: Would this 
be a good place to specify "inverse regression of regional records 
against hemispheric mean data? It needs to be clarified because I dont 
want this to be cited showing
that inverse regression (and tls since its more similar to inverse than 
forward regression) perform poorly - me and other
people like Francis Zwiers seem to find other things.
\

p. 11, left column 2nd paragraph: while HPC 2000 reconstruction is 
generally at the lower end (NOTE HOWEVER,
THAT IT REPRESENTS MORE VARIABLE EXTRATROPICAL LAND TEMPERATURES).

p. 11, right column end of 1rst paragraph: how can we know that MSH, HCA 
and union overestimates correlations?
We dont know the true ones (given the shortness of obs)....so replace 
with something more qualitative like may over
estimate it?

Conclusions, end of first paragraph: How about again adding a reference 
to the diffeerent targets of reconstruction,
eg "... others no more than 0.2K. NOte, however, that a direct 
comparison is difficult given that different reconstructions represent 
different areas of the globe."
Conclusion, 4rth paragraph: we have found that inverse regrssion of 
regional records on hemispheric mean tends to...

MARTIN, up to here and in methods, there is no equation etc for total 
least squares. So how can Gerd conclude its
wrong???

Thanks so much for all the hard work, sorry I didnt get a chance to 
carefuly read it last round since I was buried
in IPCC. I hope its not too late - its all small changes anyway, should 
t upset any reviewers!

Gabi



>
> Martin Juckes wrote:
>
>> Hello,
>>
>> 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.
>>
>> cheers,
>> Martin
>>  
>>
>

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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  
email: hegerl@duke.edu, http://www.env.duke.edu/faculty/bios/hegerl.html


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