From	Edward R. Cook	Date	Wed, 3 Sep 2003 08:32:11 -0400
To	Keith Briffa
Subject	An idea to pass by you
Hi Keith, After the meeting in Norway, where I presented the Esper stuff as described in the extended abstract I sent you, and hearing Bradley's follow-up talk on how everybody but him has fucked up in reconstructing past NH temperatures over the past 1000 years (this is a bit of an overstatement on my part I must admit, but his air of papal infallibility is really quite nauseating at times), I have come up with an idea that I want you to be involved in. Consider the tentative title: "Northern Hemisphere Temperatures Over The Past Millennium: Where Are The Greatest Uncertainties?" Authors: Cook, Briffa, Esper, Osborn, D'Arrigo, Bradley(?), Jones (??), Mann (infinite?) - I am afraid the Mike and Phil are too personally invested in things now (i.e. the 2003 GRL paper that is probably the worst paper Phil has ever been involved in - Bradley hates it as well), but I am willing to offer to include them if they can contribute without just defending their past work - this is the key to having anyone involved. Be honest. Lay it all out on the table and don't start by assuming that ANY reconstruction is better than any other. Here are my ideas for the paper in a nutshell (please bear with me): 1) Describe the past work (Mann, Briffa, Jones, Crowley, Esper, yada, yada, yada) and their data over-laps. 2) Use the Briffa&Osborn "Blowing Hot And Cold" annually-resolved recons (plus Crowley?) (boreholes not included) for comparison because they are all scaled identically to the same NH extra-tropics temperatures and the Mann version only includes that part of the NH (we could include Mann's full NH recon as well, but he would probably go ballistic, and also the new Mann&Jones mess?) 3) Characterize the similarities between series using unrotated (maybe rotated as well) EOF analysis (correlation for pure similarity, covariance for differences in amplitude as well) and filtering on the reconstructions - unfiltered, 20yr high-pass, 100-20 bandpass, 100 lowpass - to find out where the reconstructions are most similar and different - use 1st-EOF loadings as a guide, the comparisons of the power spectra could also be done I suppose 4) Do these EOF analyses on different time periods to see where they differ most, e.g., running 100-year EOF windows on the unfiltered data, running 300-year for 20-lp data (something like that anyway), and plot the 1st-EOF loadings as a function of time 5) Discuss where the biggest differences lie between reconstructions (this will almost certainly occur most in the 100 lowpass data), taking into account data overlaps 6) Point out implications concerning the next IPCC assessment and EBM forcing experiments that are basically designed to fit the lower frequencies - if the greatest uncertainties are in the >100 year band, then that is where the greatest uncertainties will be in the forcing experiments 7) Publish, retire, and don't leave a forwarding address Without trying to prejudice this work, but also because of what I almost think I know to be the case, the results of this study will show that we can probably say a fair bit about <100 year extra-tropical NH temperature variability (at least as far as we believe the proxy estimates), but honestly know fuck-all about what the >100 year variability was like with any certainty (i.e. we know with certainty that we know fuck-all). Of course, none of what I have proposed has addressed the issue of seasonality of response. So what I am suggesting is strictly an empirical comparison of published 1000 year NH reconstructions because many of the same tree-ring proxies get used in both seasonal and annual recons anyway. So all I care about is how the recons differ and where they differ most in frequency and time without any direct consideration of their TRUE association with observed temperatures. I think this is exactly the kind of study that needs to be done before the next IPCC assessment. But to give it credibility, it has to have a reasonably broad spectrum of authors to avoid looking like a biased attack paper, i.e. like Soon and Balliunas. If you don't want to do it, just say so and I will drop the whole idea like a hot potato. I honestly don't want to do it without your participation. If you want to be the lead on it, I am fine with that too. Cheers, Ed -- ================================== Dr. Edward R. Cook Doherty Senior Scholar and Director, Tree-Ring Laboratory Lamont-Doherty Earth Observatory Palisades, New York 10964 USA Email: drdendro@ldeo.columbia.edu Phone: 845-365-8618 Fax: 845-365-8152 ==================================