From	Michael E. Mann	Date	Mon, 14 Feb 2005 11:37:07 -0500
To	Tom Wigley
CC	Phil Jones, Keith Briffa
Subject	Re: WSJ
A good comparison of all of the reconstruction constructive by William Connelly, which makes it clear that the take-home point is robust, is available here: [1]http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png mike At 10:58 AM 2/14/2005, Tom Wigley wrote: Mike, I'm sorry we had no time to talk at Stanford. Here is the answer to the LIA bounce back idea ... For 20th century warming to be a bounce back, the heat must come from somewhere. The only source consistent with the bounce back idea is the ocean. The Levitus data show that heat has been going INTO the ocean, not coming out of it. This is really obvious, but I have never seem it stated anywhere. ---------- Re WSJ. They say ... "Statistician Francis Zwiers of Environment Canada, a government agency, says he now agrees that Dr. Mann's statistical method "preferentially produces hockey sticks when there are none in the data." Dr. Mann, while agreeing that his mathematical method tends to find hockey-stick shapes, says this doesn't mean its results in this case are wrong. Indeed, Dr. Mann says he can create the same shape from the climate data using completely different math techniques." ----------------- It is a bit worrying that Francis agrees with M&M -- but it seems that you do too. My questions are: (1) Do other reconstructions (not including Lonnie Thompson's of course) suffer from this standardization problem? (2) You have stated that simply averaging the data together gives the same result. Has this elementary method been published? (2a) I note that the PC1 amplitude time series invariably correlates highly with the (non-areally-weighted) 'area average'. So this brings up the issue of whether you use some area weighting in your PCA -- as we invariably do when doing PCA of gridded data? (3) From what I can see without reading their full GRL paper, M&M think that the RE statistic has an odd sampling distribution. It is easy to show this by Monte Carlo simulation -- have you done this (i.e., in the abstract, as a statistical exercise, not for the specific case of MBH98, etc.)? Tom. ______________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137 [2]http://www.evsc.virginia.edu/faculty/people/mann.shtml References 1. http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png 2. http://www.evsc.virginia.edu/faculty/people/mann.shtml