From	Valerie Masson-Delmotte	Date	Fri, 30 Jun 2006 13:46:45 +0200
To	Keith Briffa
Subject	warning - more reviews for you
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. 6-687 A 26:18 28:19 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 6-694 A 27:0 33: 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)] 6-695 A 27:0 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)] 6-696 A 27:0 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)]