cc: Martin Juckes , 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: Wed, 13 Jun 2007 10:49:08 -0400 from: Gabi Hegerl subject: Re: Mitrie revision to: Gabi Hegerl Hi all,rest of comments (and sorry its a few comments, last time this came around I was solidly buried in IPCC and couldnt look as closely at this as I should have, APOLOGIES! NOte that all changes I suggest are really small fry, so I hope its not too late. The two that are more important to me is to make sure we dont sound like we question 4AR conclusions (at least not with me as author on it), and that it doesnt sound like all inverse regression approaches have problems. The latter can be avoided if its a bit more specific about what particular inverse regression appraoch was used! Gabi > > 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). Later, some of the errors here are fixed, so just the first sentence needs some revisiting. p. 3, right column, 3rd paragraph where you discuss the IPCC TAR conclusions: I think its essential to add that the IPCC conclusions were not based on Mann et al alone - this is a misunderstanding that is propagated and caused by the SPM showing only Mann's figure, but the chapter in the background show also Briffa and Jones (fig 3.21 or so, although in low-pass resolution) - this could be clarified by changing the sentence: MBH1998 and MBH1999 have been.... since the latter was cited in IPCC2001 though the IPCC conclusions were based on several reconstructions and weaker than those of MBH1999. Footnote 2 same page: I like the footnote about uncertainty, could we add to make it to: "...,which should include expert assessment aof the robuistness of statistical methods employed AND REMAINING UNCERTAINTIES, in addition to results of statistical tests (Manning etc) p. 4, right column, boreholes last sentence - I think there is no question that the stationarity condition at the beginning influences the initial stage or boreholes, so I wonder if "may influence" should change to "will influence" - but up to you guys! (note that based on forcing, we do expect conditions before to have been warmer rather than stationary...) p. 5, end of 2nd paragraphL: Talking about the extended period of large scale warmth - should this also cite Osborn and Briffa, 2006? p. 5, bottom of right column: According to my paper table 1, Esper et al correlates ~0.5 with Mann and 0.3 with Moberg on 20-yr smoothed data - "but has greater centennial variability" doesnt capture that entirely. should we add "but somewhat less on longer timescales? Just a suggestion, no strong feelings! p. 6, bottom left colum: The variance matching thus represents a form of crossvalidation - I dont understand how variance matching could be any calibration? Interannual variablity will be influenced by the trends... unless you take them out prior to calculating the variance? Section 2.7, when discussing that the oerlemanns lies midway between MBH1999 and HPS: Its not really a fair comparison given that OER is global (?) and HPS NH land! So maybe add that information right there, saying "However, HPS represents NH extratropical land, while OER represents global temperatures. I also now think I remember that Mann and Jones discuss that it matters what a reconstruction represents (with land and extratropics leading to higher variability eg)_ p. 7. right column: "The trend component 1000 to 1850 is, however, in all reconstructions larger than the trend implied by the forcings" - I am not sure, is this shown in Nanne's paper? If yes, maybe cite? I dont find this, but then I scale... p. 9, top left: The borehole reconstructions, however, imply that there were colder temperatures experienced in the 16th to 18th centuries - actually, most other recons impy that as well, so should we add this "The borehol reconstructions and many other reconstructions, however, imply..."? p. 10, right column: .. this time using inverse regression: Would this be a good place to specify "inverse regression of regional records against hemispheric mean data? It needs to be clarified because I dont want this to be cited showing that inverse regression (and tls since its more similar to inverse than forward regression) perform poorly - me and other people like Francis Zwiers seem to find other things. \ p. 11, left column 2nd paragraph: while HPC 2000 reconstruction is generally at the lower end (NOTE HOWEVER, THAT IT REPRESENTS MORE VARIABLE EXTRATROPICAL LAND TEMPERATURES). p. 11, right column end of 1rst paragraph: how can we know that MSH, HCA and union overestimates correlations? We dont know the true ones (given the shortness of obs)....so replace with something more qualitative like may over estimate it? Conclusions, end of first paragraph: How about again adding a reference to the diffeerent targets of reconstruction, eg "... others no more than 0.2K. NOte, however, that a direct comparison is difficult given that different reconstructions represent different areas of the globe." Conclusion, 4rth paragraph: we have found that inverse regrssion of regional records on hemispheric mean tends to... MARTIN, up to here and in methods, there is no equation etc for total least squares. So how can Gerd conclude its wrong??? Thanks so much for all the hard work, sorry I didnt get a chance to carefuly read it last round since I was buried in IPCC. I hope its not too late - its all small changes anyway, should t upset any reviewers! Gabi > > 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