date: Mon, 24 Jul 2006 15:06:44 -0400 from: "Wahl, Eugene R" subject: RE: confidential to: "Keith Briffa" Thanks to you Keith, for all the huge volume of work you have done/are doing on this -- even before it became a special target for review. I'll be happy to look over the materials. Peace, Gene Dr. Eugene R. Wahl Asst. Professor of Environmental Studies Alfred University 607-871-2604 1 Saxon Drive Alfred, NY 14802 ________________________________ From: Keith Briffa [mailto:k.briffa@uea.ac.uk] Sent: Mon 7/24/2006 2:40 PM To: Wahl, Eugene R Subject: RE: confidential Will pass all comments to you before they are fixed in stone- nothing from review article will be mentioned. Really grateful to you - thanks Keith At 05:08 22/07/2006, you wrote: >Hi Keith: > >Glad to help. (!) > >If I could get a chance to look over the sections of my text you >would post to the comments before you do, I would appreciate it. If >this is a burden/problem let me know and we'll work it out. > >If it is anything from the Wahl-Ammann paper, of course that is fine >to use at once since it is publicly available. There will only be >exceedingly minor/few changes in the galleys, including a footnote >pointing to the extended RE benchmarking analysis contained in the >Ammann-Wahl review article. > >What I am concerned about for the time being is that nothing in the >review article shows up anywhere. It is just going in, and >confidentiality is important. The only exception to this are the >points I make in my blue comments in the big review file on page >104, concerning the MM way of benchmarking the RE statistic. Those >comments are fine to repeat at this point. [Please excuse my >hesitance in this way.] > >Actually, all the other blue comments I made in the big review file >are also fine to use at once. > > >Again, if this request is in any way a problem, let me know and >we'll figure out something. > > >Peace, Gene >Dr. Eugene R. Wahl >Asst. Professor of Environmental Studies >Alfred University > >________________________________ > >From: Keith Briffa [mailto:k.briffa@uea.ac.uk] >Sent: Fri 7/21/2006 2:00 PM >To: Wahl, Eugene R >Subject: RE: confidential > >Gene >your comments have been really useful and reassuring that I am not >doing MM a disservice. I will use some sections of your text in my >comments that will be eventually archived so hope this is ok with >you. I will keep the section in the chapter very brief - but will >cite all the papers to avoid claims of bias. I really would like to >discuss the whole issue of the reconstruction differences at a later >, less stressful time. I completely accept the arguments about the >limitation in the r2 and the value of capturing longer-term variance >. I think I will have to stop now as the temp and humidity are killing here. > >Thanks a lot again > >Keith > >At 18:39 21/07/2006, you wrote: > >Hi Keith: > > > >I'm sorry that there is a bit to digest...although I know it is just > >a result of the nature of things. > > > >By the way, copied below is a synopsis that I sent this morning to a > >person in DC who is working on all this with regard to the House of > >Representative hearings. Evidently, there is to be at least one > >more hearing next week, and Mike Mann will go. The person I sent > >this to is trying to understand the importance of the proxy PC > >issues --especially how, no matter what way the PC extraction is > >done, the reconstructions converge if the structures actually > >present in the data are not tossed out by truncating the number > >retained PCs at a too low level. What I've copied is this > >synopsis. I think it is straightforward -- maybe a bit dense, but > >at least brief. > > > >Also, let me know if I can help on the issue of RE vs r^2. I could > >write a few brief sentences as something for you to look at if you > >would like. Wahl-Ammann show very clearly that there is objectively > >demonstrated skill at the low-frequency level of the verification > >period mean for all the MBH segments, although the earlier MBH > >segments do have really low r^2 values (indicating very little skill > >at the interannual level). Our argument that to throw out the > >reconstruction completely based on the fastest varying frequency, > >when it has objectively demonstrable meaning at lower frequencies, > >is to me quite reasonable. That it is some how entirely ad hoc, as > >McIntyre claims in one (more?) of his comments, is neither logical > >nor factual in my perspective. The idea of frequency dependent > >skill/non-skill is not new to the literature, and the independent > >re-reviewer that Steve Schneider had look over Wahl-Ammann said s/he > >had experienced this issue in his/her work. G. > > > > > >****************************** COPIED TEXT ****************************** > > > >What it boils down to in the end is as follows: > > > >1) The different reference periods used to calculate proxy PCs from > >N. America (calibration only for MBH, full period for MM) only have > >the effect of re-arranging how the hockey stick shape appears across > >the rank ordering of PCs. In MBH it is concentrated in PC1. In the > >full-period method, it is spread over PCs 1 and 2. If one adds PCs > >1 and 2 (either arithmetically or as vectors) from either > >convention, you get an essentially IDENTICAL time series, only the > >amplitudes are a bit different. [Note that the input data were > >centered AND standardized before being put into the PC calculation > >algorithm. This is important, as shown below.] > > WHEN ACTUALLY USED IN THE RECONSTRUCTION, THE DIFFERENCE > > IS MINISCULE -- MBH is colder over 1400-1449 by 0.05 degrees! > > > >2) IF the data are centered but NOT standardized and are input into > >in a PCA algorithm using the variance-covariance matrix and not the > >correlation matrix (the way MM did it), then the hockey stick shape > >shows up in PC4. MM in fact reported this first in their 2005 > >Energy and Environment article. In effect, the first two PCs are > >ARE ACTING TO DO THE STANDARDIZING OF THE DATA not done as a > >pre-processing step. [When the correlation matrix is used instead > >in the PCA algorithm, then the standardization is in effect done by > >the algorithm, because all the correlations are "standardized" by > >construction--they all range between 0 and 1.] > > When 4 PCs from this calculation method are used rather > > than 2 PCs calculated as above, then the RECONSTRUCTION CONVERGES > > TO THE SAME AS ABOVE. > > > >3) Thus, all the different "flavors" for PC extraction have > >essentially no effect on reconstruction when one does the exercise > >of adding PCs sequentially from 2 to 5 for any flavor. In the case > >of (1), the reconstructions converge by the second PC. In the case > >of (2), they converge by PC4. They don't change with higher order > PCs added. > > THIS SHOULD BE EXPECTED FROM FIRST PRINCIPLES. That is, > > the same underlying information is there in all cases, it is only > > how the structures present in these data are spread across the rank > > order of PCs, as explained. The simple exercise of taking the > > reconstructions to convergence across the number of PCs used shows > > this clearly. > > > >4) In fact, MM essentially say all this in the 2005 EE > >article--INCLUDING ABOUT THE RECONSTRUCTION RESULTS -- but they > >strongly claim that the movement of the hockey stick shape to the > >4th PC shows it is not a leading pattern of variance as MBH claim, > >and thus should not be used. This might be logical if their > >analysis was an apples-apples comparison, but it is not, due to the > >PCA method they use and applying it on NON-standardized data. > > THESE TWO DIFFERENCES (which one can only fully get > > from their actual code, not in the articles published) DRIVE THEIR > > ENTIRE ARGUMENT ON THIS PARTICULAR ISSUE. What they do not say is > > that convergence to something like the MBH result is expectable, > > and indeed MUST happen given the data used, because the hockey > > stick shape is actually IN the data, it is NOT an artifact of PC > > calculation procedure. > > > > > >5) FINALLY, note that all of this rests on the foundation that > >keeping the bristlecone pine records in the data is appropriate, > >which Caspar and I find can be reasonable presumption. If one > >believes that the bristlecone data should be removed, then the > >1400-1449 reconstruction does not pass verification testing with the > >RE statistic, and the MBH reconstruction should commence from 1450 on out. > > > >Although there are a number of reasons to keep the bristlecone data > >in, maybe the most compelling reason they are a NON-ISSUE is that, > >over the common period of overlap (1450-1980), the reconstruction > >based on using them from 1400-1980 is very close to the > >reconstruction based on omitting them from 1450-1980. Since the > >issues about the bristlecone response to climate are primarily about > >1850 onwards, especially 1900 onwards [KEITH -- PLEASE LET ME KNOW > >IF I AM NOT ACCURATE IN THIS], there is no reason to expect that > >their behavior during 1400-1449 is in any way anomalous to their > >behavior from 1450-1850. Thus, THERE IS NO REASON TO THINK THAT THE > >BRISTLECONES ARE SOMEHOW MAKING THE 1400-1449 SEGMENT OF THE MBH > >RECONSTRUCTION BE INAPPROPRIATELY SKEWED. > > > > > >****************************** END OF COPIED TEXT ******************* > > > >Peace, Gene > >Dr. Eugene R. Wahl > >Asst. Professor of Environmental Studies > >Alfred University > > > >607-871-2604 > >1 Saxon Drive > >Alfred, NY 14802 > > > >________________________________ > > > >From: Keith Briffa [mailto:k.briffa@uea.ac.uk] > >Sent: Fri 7/21/2006 4:51 AM > >To: Wahl, Eugene R > >Subject: RE: confidential > > > > > > > >Gene > >thanks a lot for this - I need to digest and I will come back to you. > > > >thanks again > >Keith > >-- >Professor Keith Briffa, >Climatic Research Unit >University of East Anglia >Norwich, NR4 7TJ, U.K. > >Phone: +44-1603-593909 >Fax: +44-1603-507784 > >http://www.cru.uea.ac.uk/cru/people/briffa/ -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 http://www.cru.uea.ac.uk/cru/people/briffa/