From: Valérie Masson-Delmotte <Valerie.Masson@cea.fr>
To: Keith Briffa <k.briffa@uea.ac.uk>
Subject: warning - more reviews for you
Date: Fri, 30 Jun 2006 13:46:45 +0200
Reply-to: Valerie.Masson@cea.fr

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Dear Keith,

I hope that you had a good trip back from Bergen.

Some of the review comments which appeared to be relevant for the 
Holocene section are yours. I copy them here so that you can take there 
of them.

All the best,

Valérie.

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Replace "limiting the vallue" on line 18 to "review as a" on line 19 by 
"which means there is no legitimate"

[VINCENT GRAY (Reviewer’s comment ID #: 88-774)]

	

FOR KEITH


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Section 6.6.1.1 (on 2000-yr proxy reconstructions) is a little too long. 
It can be either shortened or reorganized into 2 or more shorter 
sections, say on reconstruction history, debate, and new development.

[Govt. of United States of America (Reviewer’s comment ID #: 2023-407)]

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Fig. 6.10a. Rather than showing the average of 4 European stations I 
suggest to plot the available averaged European mean land temperature 
(using much more than just 4 stations) from Luterbacher et al. 2004 and 
Xoplaki et al. 2005. This continental scale average would provide a more 
appropriate overview for the last 250 years. The first lead author has 
the data or they can be obtained prepared from xoplaki@giub.unibe.ch or 
juerg@giub.unibe.ch. Xoplaki, E., Luterbacher, J., Paeth, H., Dietrich, 
D., Steiner N., Grosjean, M., and Wanner, H., 2005: European spring and 
autumn temperature variability and change of extremes over the last half 
millennium, Geophys. Res. Lett., 32, L15713. Luterbacher, J., Dietrich, 
D., Xoplaki, E., Grosjean, M., and H. Wanner, 2004: European seasonal 
and annual temperature variability, trends and extremes since 1500, 
Science, 303, 1499-1503.

[Jürg Luterbacher (Reviewer’s comment ID #: 151-8)]

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Fig 6.10. I here repeat a point made in my comments on the FOD. It is 
statistically invalid and visually misleading to overlay the black 
instrumental line on this diagram. The coloured graph lines show proxy 
records that end at 1980. If you want a line that continues up to more 
recent years that then you must use the proxy records that continue past 
1980, not switch to a different type of series. There are up to date 
proxy records available, but as I'm sure the authors of this chapter are 
aware, they depart from the surface instrumental record, many of them 
declining after 1980. By failing to show this, and including the surface 
temperature data in black, it constitutes a misrepresentation, since the 
black line is an invalid forward extrapolation of the proxy data. If the 
reason for not showing the updated proxies is that they are not 
considered to be good representatives of temperature anymore, then by 
what right does the Figure insinuate that they were good proxies 8-10 
centuries ago? It is no defence to claim that MBH99 established a 
statistically skillful relationship between the proxy network and the 
instrumental data, since that claim has been refuted, as discussed 
above. McIntyre and McKitrick (2005a,d) showed that the pre-1450 RE 
statistic was incorrectly benchmarked, yielding a spurious inference, 
and the r2 stat calculated by MB&H themselves, which showed the lack of 
skill, was simply not reported. The failure of the r2 and CE stats is 
confirmed by Wahl and Ammann. The squared correlation between the MBH 
long proxies and the instrumental record is nearly zero (MM05a,c). The 
mean correlation between the long NOAMER proxies and gridcell 
temperatures in the MBH98 data set (which dominate the pre-AD1450 
portion) is -0.08 (McIntyre and McKitrick 2005c), and the RE 
significance benchmark is above the MBH98 RE score, using all available 
implementation of the Mann code (McIntyre and McKitrick 2005d). The 
surface instrumental record cannot be used as a statistically valid 
extrapolation for the proxies after 1980.

[Ross McKitrick (Reviewer’s comment ID #: 174-35)]



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