date: Fri, 23 Oct 2009 09:40:32 +0100 from: Rob Wilson subject: Re: CA - Polar CRN to: Tom Melvin Hi Tom, here are a copy of my two posts this week. I am now ignoring CA as I have lectures to prepare for next week. :-( #1 from "The NAS Panel and Polar Urals" Dear Steve et al. As a response to your recent posts and also to your private e-mails, here's my 10 cents towards the use of the Yamal and/or Polar Urals data. I will admit that the data description (Figure 2 and Table 1) in D'Arrigo et al. (2006) is somewhat misleading. For those who have not read the paper [1]http://www.st-andrews.ac.uk/~rjsw/all%20pdfs/DArrigoetal2006a.pdf we derived two NH reconstructions. One using TR chronologies developed using traditional individual series detrending methods (STD) and another that solely used TR chronologies that had been processed using the RCS method. The latter method being theoretically better to capture more low frequency information. I think our paper clearly shows this. For all locations except the Polar Urals and the Alps, we used the same data to derive the STD and RCS flavours. As we have discussed through CA before, I was not happy with the resultant RCS chronology using the Polar Urals data. I know you do not agree with my decision here. Anyway, the Yamal series represented a RCS chronology from a nearby location. The figure below show the strong coherence between the Polar Urals STD and Yamal RCS series. Polar Urals STD vs Yamal RCS Unfortunately, in the paper we failed to clarify that different data were used for the STD and RCS versions for the location we labelled the Polar Urals. The replication data in Figure 2 are from the Polar Urals data. Please note that the situation exists for the Alps. The historical spruce data detailed in Wilson and Topham (2004) did not perform well using the RCS method, so instead we used a different species chronology (Nicolussi and Schiessling 2001) for the RCS version. So - to clarify - in Figure 2, the replication histograms are relevant for both the STD and RCS flavours for each site EXCEPT POL and ALPS where the replication is only relevant for the STD versions. I will not be troubling the journal with a corrigendum as it does not change the results of the paper at all. Finally, I want to clarify that I never asked Keith Briffa for the raw Yamal data. The simple fact of the matter is, I have great respect for Keith and I saw no point at the time in asking for raw data when there was a published RCS chronology for that location. Rob #2 from "Re-Visiting the "Yamal Substitution"" Dear All, I think I need to clarify a few things as Steve has only given you a select amount of information. As you know, I often reply to Steve privately as it is too time consuming to place a post on this blog due to all the replies that are generated. I just do not have time to reply to all the questions. So.... 1. Firstly, the decision to use Yamal was both mine and Rosanne's and we do not regret this decision. 2. Please do not forget that DWJ2006 did in fact use BOTH the Polar Urals and Yamal data - the former for the STD version and the latter for the RCS version. 3. The variance heteroscedasticity issue was not the only reason why I used the Yamal chronology compared to the RCS generated version of the Polar Urals. I also undertook local calibrations against June-July mean temperatures: 1883-1970 Polar Urals: r = 0.53 / DW = 1.62 / linear trend in residuals - r = -0.18 (ns) Yamal: r = 0.63 / DW = 1.75 / linear trend in residuals - r = -0.05 (ns) 1883-1990 Polar Urals: r = 0.53 / DW = 1.54 / linear trend in residuals - r = -0.16 (ns) Yamal: r = 0.61 / DW = 1.69 / linear trend in residuals - r = -0.08 (ns) So - Yamal was also simply a better estimate (albeit slight) of local summer temperatures. NB. These correlation results are a little different from Steve's - differences of CRU2 vs CRU3 and period analysed??? 4. It might take me a couple of weeks as I am busy with teaching at the moment, but I will re-calculate the DWJ2006 RCS reconstruction using the POL RCS series instead of Yamal. As we weight the data equally between North America and Eurasia, I am pretty sure that the final outcome will not be that different. Certainly, the MWP values will be slightly higher but it will not change the conclusions of the paper - which - I would like to remind everyone - we were quite explicit in saying that prior to ~1300, the reconstruction estimates should be interpreted cautiously. 5. Hey - In fact - for the hell of it, I might swap our RW Tornetrask series with Hakan Grudd's version. I can include new data from central Asia and Europe and North America. Will the final result change significantly - I very much doubt it. Please understand that palaeoclimatology (and science as a whole) is not static. We are continually updating and adding new data-sets. No one paper should ever be treated as the be all and end all. While Steve is mired in the past, we are trying to improve on the uncertainties - not "moving on" as I am sure you will banter around, but simply trying to improve on what has been done before. 6. Finally, devote followers of this blog seem to be obsessed with an elevated MWP. It is stated so very often that we are "cherry picking" purposely to deflate the MWP. This is simply not the case. In fact, the fatal flaw in this blog and what keeps it from being a useful tool for the palaeoclimatic and other communities is its persistent and totally unnecessary negative tone and attitude, and the assumption that our intention is faulty and biased, which keeps real discourse from taking place. Rob Tom Melvin wrote: Rob, At some stage I expect to have to explain why Yamal is better that Polar Urals. I seem to think you discussed Polar on CA site. Have you a copy of what you said? We need to reinforce each other. Tom Dr. Tom Melvin Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593161 Fax: +44-1603-507784 -- ----------------------------------------------------------------------- Dr. Rob Wilson Lecturer in Physical Geography School of Geography & Geosciences University of St Andrews St Andrews. FIFE KY16 9AL Scotland. U.K. Tel: +44 01334 463914 Fax: +44 01334 463949 [2]http://www.st-andrews.ac.uk/gg/people/wilson/ ".....I have wondered about trees. They are sensitive to light, to moisture, to wind, to pressure. Sensitivity implies sensation. Might a man feel into the soul of a tree for these sensations? If a tree were capable of awareness, this faculty might prove useful. " "The Miracle Workers" by Jack Vance ----------------------------------------------------------------------- Embedded Content: PUvsYAM.gif: 00000001,242841b0,00000000,00000000