Monday, May 7, 2012


cc: "Malcolm K. Hughes" <>, Crowley_Hegerl <>,,, Jan Esper <>,,,
date: Mon, 10 Sep 2001 14:51:08 -0400
from: Ed Cook <>
subject: Re: Esper/Cook paper
to: "Michael E. Mann" <>

Hi Mike et al.,

Okay, here is an overlay plot of MBH vs. RCS, with RCS scaled to the
1900-1977 period of MBH, and with 95% confidence limits. This has been done
for the 40-yr low-pass RCS data to be consistent with the low-pass MBH
series you sent me. The 95% confidence limits of the RCS are also scaled
appropriately. Since correlations with both instrumental and MBH are
O(0.95) after even 20-year smoothing because of the trend, the RCS limits
are effectively based on the bootstrap 95% limits of the 14 chronologies.
Assuming that the original RCS C.I.s are reasonably accurate (which I think
they are), what is apparent (to me anyway) is that the confidence limits of
MBH are uniformly narrower after AD 1600. Prior to that, they are
comparable to RCS back to ca. AD 1200 where RCS C.I.s get bigger. Of course
this is an odd comparison because the confidence limits are not derived the
same way. However, I do think that they are somewhat informative
nonetheless. What is also apparent is the much great amplitude of
variability in the RCS estimates. This is consistent with the understanding
that extratropical temperatures are more variable than tropical
tempertures, which supports the idea that the MBH record does have more
tropical temperature information in it. The other interesting thing about
expressing the RCS data this way and overlaying it on MBH is the appearance
that MBH is missing the LIA rather than the MWP, at least on
multi-centennial timescales. This turns some of Broecker's criticism of the
"hockey stick" on its head. I'm not sure where all this leads.

Any comments and further suggestions are welcome as long as they come in by
tomorrow. I am definately submitting the paper within a day or two.



Attachment Converted: "c:\eudora\attach\Fig5.plt_eps1.eps"
Dr. Edward R. Cook
Doherty Senior Scholar
Tree-Ring Laboratory
Lamont-Doherty Earth Observatory
Palisades, New York 10964 USA
Phone: 845-365-8618
Fax: 845-365-8152

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