date: Thu, 28 Jun 2007 11:19:31 -0600 from: Kathreen Ruckstuhl subject: Re: Philosophical transactions to: Tom Melvin , Keith Briffa Dear Keith and Tom, Please find below the last reviewer's comments on your paper. Please also make sure that you deal with them and send me a list of the changes you made. This also applies to the minor changes suggested by the first reviewer. Best wishes and thanks again for this excellent contribution! Kathreen Review of `Trends in recent Temperature and Radial Tree Growth spanning 2000 years across Northwest Eurasia`, by Keith R. Briffa et al. General Comments Overall, I liked the paper. I value the findind that the strenght of climate-tree growth relationships has not declined during the 20th century, as this has been the cause of debate in the last years since a paper published ironically by the same author in 1998 (Briffa et al. 1998). This gives tree-ring-based temperature reconstructions in the area credibility and enables the authors to state that the 20th century has been unprecedented in terms of high temperatures in the last 2 millenia in NW Eurasia. The analyses are easy to understand, practical and useful in getting to the point of the paper. I have no major comments in a general sense. Sometimes the text might be a bit confusing, the sentences too long and grammatically complex, with some commas missing that make things difficult to understand, and the structure of the paper not pertfectly fluid, but I would not say it represents a problem overall. My only comments are punctual and come here: Particular comments *1.* Page 3. Lines 10-12. This sentences refer to the Arctic Amplification: the Arctic amplification has caused a great debate in the last decade which does not appear in here. Whereas many authors claim that temperatures in Northern latitudes will increase more than in the temperate areas due to the ice-albedo feedback (e.g. Serreze and Francis 2006), some others claim that this is not the case in observed values (e.g. Polyakov et al. 2002). A reference to this debate could be useful. *2.* Page 5. Line 2. Erase the word ‘that’ or else the sentence is not comprehensible. *3.* Page 6. Lines 1-8. The ‘RCS method’ was termed this way by Briffa et al. 1992, but the same method had been applied by other authors way before (Erlandsson 1936; Fritts 1976). I would appreciate the earlier references in the text. *4.* Page 7. Line 33. I’d add a comma between ‘millenia’ and ‘two´. *5.* Page 7. Line 35 and lines 8-10. After stating that regional chronologies have practically nothing to do with each other, the authors built a NW-Eurasian chronology, which they will only use once and in a minor analysis which unnecessary for the paper’s main conclusion. I do not see the point in using that chronology, as it represents the average of three chronologies that have very little in common. *6.* Page 9. Line 17. ‘lower than’ instead of ‘lower that’. *References* * Briffa, K.R., Jones, P.D., Bartholin, T.S., Eckstein, D., Schweingruber, F.H., Karlen, W., Zetterberg, P., & Eronen, M. (1992) Fennoscandian summers from AD-500 - Temperature-changes on short and long timescales. Climate Dynamics, 7, 111-119. * Briffa, K.R., Schweingruber, F.H., Jones, P.D., Osborn, T.J., Shiyatov, S.G., & Vaganov, E.A. (1998) Reduced sensitivity of recent tree-growth to temperature at high northern latitudes. Nature, 391, 678-682. · Erlandsson, S. (1936) Dendrochronological studies. Report 23. Uppsala, Sweden. Stockholms Högskolas Geokronological Institute. · Fritts, H. (1976) Tree rings and climate. London: Academic Press 567 pp. · Polyakov, I. Et al. (2002) Observationally based assessment of polar amplification of global waring. Geophysical Research Letters 29(18): 1878. doi 10.1029/2001GL011111 · Serreze, M. And J.A. Francis. (2006) The Arctic Amplification Debate. Climatic Change 76: 241-264. Attachment Converted: "c:\eudora\attach\kruckstu6.vcf"