cc: anders@misu.su.se, Eduardo.Zorita@gkss.de, esper@wsl.ch, k.briffa@uea.ac.uk, m.allen1@physics.ox.ac.uk, weber@knmi.nl, t.osborn@uea.ac.uk date: Tue, 12 Jun 2007 17:39:02 -0400 from: Gabi Hegerl subject: Re: Mitrie revision to: Martin Juckes Hi Martin et al., I have a few comments, that will probably come in two emails since I need to run soon. I am sorry they are a bit late, but I think its only words anyway, so I hope its ok! Gabi Abstract: I think what got to the reviewer was the maximum temperature given by 3 significant digits, I doubt we can know it that well - how about saying 0.25 K (relative..) (and the residual on 2 digits as well)? Also, procedure (1) is, as far as I can tell, inverse regression of regional records on hemispheric mean (if I understand right) - this is nowhere fully spelled out, but should be spelled out I think. If you, for example, were to composite and then inverse regress the composited average record, you would get something identical to your (2) but with more variance (and something much closer to my paper and I think that works pretty well as well, but no need to argue for that here at all, just could we please be specific and say in abstract and once in main text what we regress inversely? It does make a difference?) Introduction, 2nd para: The dominant change... you should cite eitehr the entire IPCC report 2007 for that, or chapter 2 of it - Mitchell et al is the attribution chapter and doesnt really discuss forcing. p. 2, left column, 2nd and 3rd column: I admit I am quite unhappy with how this is phrased, and would really love to have this changed. Reading it naively, I would conclude that we cant yet estimate the anthropgoenic contribution to the late 20th century warmth, while at the same time being the first author of the chapter saying we can and its dominant ... How about replacing the first sentence of 2nd paragraph (However, there remails...) with the following: The following two questions are essential for understanding 20th century climate change and thus credibly predicting future climate changes:... Then, the beginning of the next paragraph: Despite strong results from attribution studies, some uncertainty in the answer to the first question remains.... . I think this sounds less like we question 4AR conclusions... p. 2, right column beginning of section 2: I think the attribution of timeseries to reconstruction regions is not correct everywhere. HCA2007, for example, is definitely NH extratropics (N of 30N), and if you have used "dark ages", its actually calibrated to land (does the series you use go back to the 6th century?). Also, I am nearly certain that JBB is a NH reconstruciton, and to my knowledge is HPS extratropical land as well (thats where the boreholes are). I think this paragraph needs a sentence cautioning somewhere along the line after temperature" : Note that some of the difference in variance of timeseries can be attributed to different areas resolved, the entire NH land and oceans varies weaker than, for example, NH extratropical land only (if all fails you can cite me but there's got tbe be a better citation). p. 3, left column, discussion of JOnes reconstruction: It is also shown that there are strong large scale coherencies in..proxy data... not reproduced in climate model CONTROL simulations. (please add control, I think thats what they did, and internal variability will show less spatial coherence than externally forced runs!) more in the second email Gabi and the borehole reconstruciton For increasing the credibility of answers to both questions, reconstructing and understanding climate change over a longer time horizon, such as the past millennium, is essential (Hegerl et al. 2007b) Martin Juckes wrote: >Hello, > >here is another update. I've incorporated Nanne's rewrite of the start of the >new section 4, which shortens it by a couple of sentences. > >cheers, >Martin > > -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Gabriele Hegerl Division of Earth and Ocean Sciences, Nicholas School for the Environment and Earth Sciences, Box 90227 Duke University, Durham NC 27708 Ph: 919 684 6167, fax 684 5833 email: hegerl@duke.edu, http://www.env.duke.edu/faculty/bios/hegerl.html