cc: Phil Camill , dhunzicker2002@yahoo.com date: Thu, 24 Jul 2003 15:21:55 -0500 from: Phil Camill subject: Re: Holocene manuscript- sorry to: Keith Briffa Dear Keith, I have been contacted by the lead author (D. Hunzicker), and he is enthusiastic about resubmitting after substantial revision. We feel that we can address several of the reviewers comments about sample size and core inclusion. First, we both agree that our original statement in the methods unfortunately misled the reviewers into believing that we didn't use cores with missing rings. This is not the case. Second, I wrote the section on sample size, and, unfortunately, I misinterpreted the lead author's description of how he established the chronology vis-a-vis sample size. The following explanation, which will be clarified in a potential revision, shows that we did use most (84%) of climatically sensitive cores collected: Paraphrased notes from D. Hunzicker: 1) 152 is the total number of trees I cored. Of those, I only measured the rings of 118 cores, the remaining 34 being young (mostly less than 180 years) and composed entirely or almost entirely of rapidly growing, complacent, juvenile growth rings. I, therefore, sampled 118 trees with sufficiently long (and potentially sensitive) records for dendrochronological analysis. 2) Of the 118 cores, 61 were used to establish the chronology (many with missing rings), and 57 cores were rejected due to "complacency, unresolvable sections of missing rings, or low interseries correlation values." Probably half of these 57 cores (~30) were from trees growing near the lake level or in small, potentially wetter, ravines on the slope where you would expect a weak climate signal. I cored them anyway because they were some of the largest trees in the region and to increase sample size, but I anticipated that they may be problematic, which they were. These 30 cores were therefore rejected. 3) Approximately 13 of the 57 were rejected for other reasons such as multiple breakage points. 4) The remaining 12 rejected samples were extremely difficult to include in the chronology and may heve been included had replicate cores been sampled from each tree to aid in identifying multiple sets of missing rings. Given logistical and time constraints during sampling, however, I opted for increasing the sample size of the number of replicate trees rather than pseudoreplicated cores from a single tree. It's possible we can re-investigate these 12 samples. Thus, of the 118 cores with long records, only 73 were truly suitable for analysis. Of these cores, 84% (61 cores) were used to build the chronology, only 12 cores were omitted because of being extremely difficult to include in the chronology. We would be grateful for any initial thoughts you might have. All the best, Phil --On Thursday, July 24, 2003, 1:49 PM -0500 "Phil Camill" wrote: > > Thanks, Keith. I will contact the author, D. Hunzicker, and see how he > wants to proceed. The reviews below were helpful, and we would like to > revise the manuscript to improve its quality. A first place to start will > be to simplify the approach, focusing mainly on the new chronology and its > comparison with Cook et al's data set (i.e., reviewer 2's suggestion to omit > the fft of sunspots and ENSO, which are well reviewed in the literature). > > My first read of the reviews were mixed. Reviewer 1's comments that we only > included trees with no missing rings is false. Our chronology includes > several cores with missing rings but where identifying and incorporating > missing rings was fairly straightforward. And there were plenty of hard > hours at the scope looking for and incorporating them. Perhaps we should > back off our statement about omitting cores with "complacency, unresolvable > sections of missing rings, or low interseries correlation values" which was > obviously misleading. Nonetheless, there will always be cores that are > simply too difficult to verify with COFECHA, and I was surprised to see > his/her reaction that 61 cores couldn't establish an adequate chronology. I > doubt there there is literature suggesting a minimum fraction of cores that > should be incorporated into a chronology. > > We will also re-analyze the response function analysis and climate data, > although our approach in examining both raw and detrended data were pretty > exhaustive. It may turn out that reviewer 1 is correct that climate data > "are not guaranteed to be homogeneous, especially in the mountain West > during the early 20th century." Given that we analyzed both pre-whitened > and standardized data sets, do you or the reviewer have additional > suggestions on how to proceed? > > If we were to undertake substantial revision in an effort to resubmit, is > there an appropriate timetable that would work for you, say our getting a > manuscript to you sometime in the next 3-5 months? > > Thanks again, Keith. > All the best, > Phil > > > > --On Thursday, July 24, 2003, 1:57 PM +0100 "Keith Briffa" > wrote: > >> >> Phil >> I am really sorry for the delay , that was a result of initially tardy >> reviewers, my subsequent illness, and then a delay while John is away > while >> I wished to consult with him . The reason for the last wish will be clear >> when you read the reviews below. >> The referees are not enthusiastic and in their private comments to me one >> is strongly negative and the other ambivalent. The pressure on space means > >> that this would normally be a rejection (and we have, since your > submission >> ,developed new , stricter rules regarding possible re-submission.) >> However, in the circumstances (the delay that is down to me) , I am >> overruling these and (despite not discussing it with John) asking you to >> read these reviews and come back with a frank opinion of whether you >> consider them fair and the paper publishable with some work . I am doing >> this because I believe it is. If you can answer these remarks and feel you > >> can submit a valid manuscript that accounts for them - I will review your >> argument (without recourse to the reviewers) and if I agree , I guarantee >> speedy process through the last publication phase. >> Again , you and I are well aware that this manuscript could have been > dealt >> with much better and I am really sorry for it. >> Keith >> >> REVIEWERS REMARKS FOLLOW >> >> Referee 1 >> >> Review of David Hunzicker and Phil Camill: "Using a new 672-year tree-ring > >> drought reconstruction from westcentral MontanaŠ" submitted to the > Holocene. >> This is a well written, well executed paper that I would unfortunately not > >> recommend for publication in the Holocene. It's a shame to read a paper >> like this. It is very well informed, well referenced, places the work in a > >> good scientific context, and includes strong statistical analyses. > However, >> the attention paid to the analyses and interpretation of the > reconstruction >> was evidently not paid so carefully to the fundamental tree-ring > chronology >> development. They call it "crossdating," but the best I can tell from the >> limited discussion it was simply computerized correlation matching of >> measured time series, with a massive culling of the data to pare down to >> those time series that produced straightforward correlations in a COFECHA >> analysis. I was astounded to read that their final chronology used only 61 > >> out of the 152 trees sampled for the study. The 60% of the trees not >> included apparently suffered from "complacency, unresolvable sections of >> missing rings, or low interseries correlation values." This appears to be >> the first penalty for not applying rigorous dendrochronological methods to > >> the chronology development. I find it incredible that over half of the >> Ponderosa pine samples would not be useful. I can't help but suspect that >> by relying on COFECHA output, without any hard-nosed microscope work and >> rigorous crossdating with the wood samples themselves, you at best default > >> to the simple, straightforward trees without missing rings. That is, you >> default to a less climatically sensitive subset of trees. This appears to >> be the second penalty for the seemingly inexpert, quick and dirty >> chronology development. >> These authors have obviously worked hard on this study and bring excellent > >> analytical skills and knowledge of the literature. The paper itself is >> exceptionally well written (with a minor complaint concerning the over > use, >> and at times incorrect use of the term "teleconnection"). But the >> calibration and validation reported in the paper are clearly awful, and >> that surely ought not be the case for Ponderosa pine on moisture-stressed >> sites in Montana. One hates to be non-supportive of their work, so much of > >> which is high quality, but it seems to come down to fundamentals, and here > >> the fundamental dendrochronology and chronology development are in >> question. And I also do not think it advisable to publish a reconstruction > >> that explains maybe 21% of the variance in the instrumental climate data, >> when using an arid site conifer as the predictor (the persistence in the >> standard chronology may be inflating even that figure). I just can't >> believe the calibration could be so weak. It seems they need to revisit >> their chronology development work, and dig deeper into the climate > response >> of their chronology. Then look very carefully at climate data itself. > These >> climate data are not guaranteed to be homogeneous, especially in the >> mountain West during the early 20th century. If all this could be done, > and >> if the variance explained in both the calibration and verification periods > >> could be improved, then publication in the Holocene would be well > justified. >> >> Referee 2 >> >> >> Review of "Using a New 672-Year Tree-Ring Drought Reconstruction from >> West-Central Montana to Evaluate Severe Drought Teleconnections in the >> Western U.S. and Possible Climatic Forcing by the Pacific Decadal >> Oscillation" by D.A. Hunzicker and P. Camill >> >> This paper is reasonably well written, but has some problems in it that >> bother me. The first issue relates to the tree-ring chronology that was >> developed at Lindberg Lake. Anytime less than half of the core samples (61 > >> or 152) are used in developing a chronology, this is cause for concern. > The >> fact that there are "unresolvable sections of missing rings" (p. 10) can >> mean a lot of things. However, ponderosa pine is known to cross-date well, > >> which includes "locating" locally-absent rings during the cross-dating >> phase, so it is surprising that the authors have chosen not to work > through >> these problems. Presumably, the trees with missing rings are also those >> most sensitive to drought, so isn't there a chance that the chronology >> being analyzed in this paper is less sensitive to drought than it ought to > >> be? I also wonder how much their chronology is truly contributing to the >> overall stated goal of this paper, i.e. evaluating "Severe Drought >> Teleconnections in the Western U.S. and Possible Climatic Forcing by the >> Pacific Decadal Oscillation". The authors extensively use the PDSI >> reconstructions of Cook et al. (1999) in their analyses. Aside from the >> increased length of their new tree-ring chronology, what does it > contribute >> that was not possible simply by using the Cook et al. reconstructions to >> test for teleconnections and forcing. None of the indices of forcing > (ENSO, >> PDO, sunspots) extend back before the beginning of the Cook et al. >> reconstructions, so there is little to be gained in using one longer > series >> from west-central Montana in this analysis. One could point to Fig. 3, >> which compares the MT reconstruction vs the SWDI series. But even this >> comparison is limited in its overall contribution to the paper. I also >> don't like the use of the FFT for estimating power spectra, even if the >> confidence limits are determined by bootstrapping. The power spectra >> calculated by the FFT are still inconsistent estimates. A more > contemporary >> and consistent method of spectral estimation, like the Multi-Taper Method, > >> should be used. >> For the reasons stated above, I do not consider this paper to be ready for > >> publication as is. I will leave it to the Editor to decide how to proceed >> with it past this point. >> >> >> >> >> >> >> >> At 10:33 PM 7/23/03 -0500, you wrote: >> >>>Dear Keith, >>> >>>I have not yet received an editorial response or reviews for the > manuscript >>>entitied "Using a new 672-year tree-ring drought reconstruction from >>>west-central Montana to evaluate severe drought teleconnections in the >>>western US and possible climatic forcing by the Pacific Decadal > Oscillation" >>>by Hunzicker and Camill. This manuscript has been in review for 14 > months. >>> >>>Can you indicate when I can expect these materials? >>> >>>Many thanks, >>>Phil >>> >>> >>> >>> >>>************************** >>>Dr. Phil Camill >>>Assistant Professor of Biology and Environmental Studies >>>Carleton College, Department of Biology >>>One North College St. >>>Northfield, MN 55057 >>>phone: (507) 646-5643 >>>fax: (507) 646-5757 >>>*************************** >> >> -- >> 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/ >> >> > > > > ************************** > Dr. Phil Camill > Assistant Professor of Biology and Environmental Studies > Carleton College, Department of Biology > One North College St. > Northfield, MN 55057 > phone: (507) 646-5643 > cell phone: (612) 578-7480 > fax: (507) 646-5757 > Camill Lab: http://www.acad.carleton.edu/curricular/BIOL/faculty/pcamill/ > Biology: http://www.acad.carleton.edu/curricular/BIOL/index.html > ENTS: http://www.acad.carleton.edu/curricular/ENTS/index.html > *************************** > ************************** Dr. Phil Camill Assistant Professor of Biology and Environmental Studies Carleton College, Department of Biology One North College St. Northfield, MN 55057 phone: (507) 646-5643 cell phone: (612) 578-7480 fax: (507) 646-5757 Camill Lab: http://www.acad.carleton.edu/curricular/BIOL/faculty/pcamill/ Biology: http://www.acad.carleton.edu/curricular/BIOL/index.html ENTS: http://www.acad.carleton.edu/curricular/ENTS/index.html ***************************