date: Tue, 14 Aug 2007 13:15:24 UT from: grlonline@agu.org subject: Review Received by Geophysical Research Letters to: t.osborn@uea.ac.uk Content-Transfer-Encoding: binary Content-Type: multipart/alternative; boundary="_----------=_1187097324177271" MIME-Version: 1.0 X-Mailer: MIME::Lite 3.01 (F2.74; B3.07; Q3.07) Date: Tue, 14 Aug 2007 13:15:24 UT Message-Id: <76118709732424@gems> Dear Dr. Osborne: Thank you for your review of "Signal strength and climate calibration of a European tree-ring isotope network" by Kerstin Treydte [Paper #2007GL031106], which we have safely received. A copy of this review is attached below for your reference. Thank you for your time and effort! Sincerely, Mark New Editor Geophysical Research Letters ------------------------------------------------------------------------ Science Category: Science Category 1 Presentation Category: Presentation Category B Annotated Manuscript: No Anonymous: No Referrals: No Confidential Referrals: Highlight: No Highlight: Formal Review: The manuscript by Treydte et al. presents new and interesting work concerning the potential for isotopic analysis of annual growth material sampled from trees to yield useful proxies for past climate variability, even at sites where the trees are not close to some physiological or ecological limits. The particular importance of this manuscript is that it considers a continental-wide network of sites, which provides for a much better assessment of the robustness of the potential climate signals and their dependence on tree genus and/or location. There are no major flaws in the manuscript and therefore I recommend that it be published in Geophys. Res. Lett. I list below a number of minor items that the authors should consider while preparing their final manuscript. (1) Abstract, line 45, and line 172: "wavelength" is ambiguous here; perhaps change to "time-scale"? (2) Line 57: surely it should be "high latitudes OR altitudes" not "AND"? (3) Line 78: "The sampling design considered not only ecologically extreme sites...". It sounds that some, perhaps previously published, analysis has been done using total ring width and/or maximum latewood density measurements from these tree sites. If so, perhaps an extra column could be added to Supplementary Table 1 to indicate whether the climatic factor found to dominate these "traditional" tree-ring measurements is one of "Temperature", "Moisture", "Mixed" or "None/Not Known"? This would help the reader who is not experienced in this area to appreciate the coverage of "extreme" and "temperate" sites in the network. (4) Line 96: Pederson et al. (2004) seems missing from the reference list, and also some references seem to be out of alphabetical order. (5) Line 102: "considered mean, min and max temperatures...we focus on the highest correlations observed for Tmax and P..." The later discussion does not present any biophysical reasoning why Tmax would influence the isotopic composition more than Tmin or Tmean. If there is no such a priori argument for the dominance of Tmax, the reader may wonder whether it is simply fortuitous that the correlations with Tmax are higher than with Tmean. If so, it would be useful to briefly note how much stronger the Tmax correlations are compared with the Tmean correlations (e.g., "the correlations with Tmean are lower by 0.XX when averaged across all sites"). (6) Line 115: use of the word "standardized" is going to cause problems here. The supplementary information indicates that, here, "standardized" simply means having the long-term means subtracted, yet clearly there is scope for confusion with the standardization used in dendroclimatology to remove age-related effects, which has not been done here. Since the correlations are unaffected by the long-term mean anyway, perhaps just change "standardized" to "raw"? (7) Line 116: apparently the rbar values shown in the supplementary information indicate little common variance, yet I think that they are reasonably strong for such a widely dispersed network as this. For comparison, perhaps the authors could note the rbar values between the instrumental records of Tmax and P for the 23 site locations; in comparison to these instrumental rbar values the tree-ring isotopic rbars may seem quite respectable. (8) Line 129: "generally WEAKER than was expected" may be less ambiguous that the current "LOWER" (what is a "lower signal"?). (9) Line 133-134: here it is stated that the temperature-precipitation correlation is higher in NW Europe than in Mediterranean Europe, but for summer (which is being used here) this may not be the case. See, e.g., fig. 2 of Briffa et al. (2002; Holocene 12, 737-757). Although this compares averages from a number of northern and mid-latitude regions, not just from Europe, since I drew the figure I have the results for the individual regions! For Briffa et al.'s "Northern Europe", r(Tmean,P) for JJA is about -0.25, while for "Southern Europe" it is -0.45. Unless the authors have done their own calculation and find different results for Tmax than for Tmean, or for their definitions of "NW Europe" and "Mediterranean", then they should correct this. (10) Line 151: should "temporarily" be changed to "temporally"? (11) Lines 161-168: the use of "LOW" loadings is confusing here, because the authors mean that they are a bit lower than the "highest" loadings, but they are still much stronger than the loadings at all the non-marked sites. Perhaps "moderately high" is better than "low"? (12) Line 181: should this be "RPC2" not "RPC3"? (13) Line 355: should this be "(Tmax)" not "(T)"?