date: Wed, 16 Jun 2004 09:50:40 -0400 from: "Michael E. Mann" subject: Re: revised manuscript to: Tim Osborn , Scott Rutherford , Bradley Raymond , Hughes Malcolm , Briffa Keith , Jones Phil , mann@virginia.edu HI Tim, Thanks--your suggestions (w/ Keith and Phil) all are very helpful, and improve the manuscript significantly. This was exactly what was needed! A couple minor clarifications on some points that were raised: 1. In discussing how spatial reconstructions are averaged to get hemispheric means, we just meant that, not that these spatial reconstructions were the results of CFR approaches. I believe it is true that Briffa et al, 1998a does average gridpoint reconstructions to get a hemispheric mean, right? We should clarify the wording to make sure that this is clear. The issue of different approaches (CFR vs local calibration) is discussed later in the paper... 2. Re, McINtyre/McKitrick: they didn't identify any "errors" at all. They (a) used an incorrect spreadsheet representation of the data (which Scott prepared based on a misunderstanding of precisely what they were looking for, since the predictors cannot be included in a single matrix because of the stepwise nature) and (b) used different versions of certain series that were on the NGDC site. There were some minor errors in the supplementary information, and we have a corrigendum in press in "Nature" that makes note of these. I agree that we should add a sentence clarifying how PCs were calculated in the PC/proxy network at the beginning of that section. 3. You're right that RE is not necessarily less than r^2 in calibration. That statement is rightfully removed... 4. I believe that including weights in the hybrid approach that are proportional to the fraction of variance resolved by the indicator is essential. In fact, we know that we get completely wild results if we don't do that. The reason is that an indicator that has essentially no low-frequency variability left (say, an already pre-whitened tree-ring chronology) has essentially only noise left in the low-frequency band. Now, if you use the weighting convention we use, it gets almost no weight. On the other hand, if you give it full weight in that band, you magnify that tiny bit of residual noise up to the full amplitude of all other indicators, and now you've got completely noise competing w/ other series that have much more signal. I think a sentence needs to be added to clarify this point, and also a sentence added that indicates that highly unconstrained results are possible if this is not done. The example of weights of 0 and 1 is an extreme limiting case, which is probably never realized (Scott?). 5., Re the ECHO-G simulations, yes we can certainly downplay the discussion of this in our response. However, I stand by the claim that they appear to use a solar forcing that is about twice that of Crowley's! In the talk they gave in Nice (Phil was there), they showed their solar constant varying between 1362 and 1368 W/m^2 over the past millennium! That is much larger than Crowley. As no details are provided in the Gonzalez-Rouco paper, this is very difficult to discern. However, the huge Medieval peak, and the claim that 40% of 20th century warming is solar-driven (they make both claims) is ONLY consistent w/ a much larger solar forcing then anyone else has used. Christiensen's group has used Crowley's forcings on the same exact model, and gets nothing near the amplitude of variability they got (like the GKSS paper, I believe this paper is in submission). There is something very odd in what the GKSS group has done, and I think Phil agrees w/ this. It would be unfortunate if the issue of precisely how large a solar forcing they used isn't examined closely before they publish their results in more detail. But I agree we don't need to get into this in the paper or the response. We can make the point, as you suggested, that as shown in Jones and Mann, the reconstructions are broadly consistent with the vast majority of simulations that have been done... I don't think it should be a problem waiting about a week for Scott to resubmit (in time for the Osborn et al '04 paper to have been submitted). We still need to give Malcolm and Ray a chance to get back w/ any additional comments, if they have them... cheers, mike At 07:00 AM 6/16/2004, Tim Osborn wrote: Dear Scott et al. the manuscript reads well - the results section in particular does a good job at presenting the sequence of many experiments in a logical and structured way. We've combined all our (me, Keith and Phil) comments together, and put them in the attached files (one for the manuscript, one for the response to the editor). Many are simple changes. Some are questions/comments for you, that I've put in CAPITALS. I've also written an improved description of the MXD data. And the "Osborn et al. (in preparation)" paper that describes the gridding and low-frequency aspects of the MXD data (as well as our "local" calibration of it) is now referred to as Osborn et al. (2004, submitted to Global and Planetary Change). It is not, in fact, submitted as I write, but should be very soon - a full draft is complete and I have comments from Phil and Fritz, and Keith is halfway through providing his comments. I'll let you know as soon as its submitted - it would be preferable if you could hold off returning your revised manuscript until we have actually sent off Osborn et al. - it should be done by the end of the week. Then "Osborn et al. (submitted)" will be true! Cheers Tim At 19:15 28/05/2004, Scott Rutherford wrote: Dear All, Attached is a revision of the Northern Hemisphere comparison for J. Climate. Also attached is a reply to reviewers. (both microsoft word format) I've been getting extensions for the submission of the revision and would like to try to get it in around June 15. If you want to make suggestions/comments directly in the text, please use Microsoft Word's "track changes" feature if possible. There are a few highlighted parts that need particular attention. Please let me know if you have question or difficulty with the files. Regards, Scott ______________________________________________ Scott Rutherford Assistant Professor Dept. of Natural Sciences Roger Williams University e-mail: srutherford@rwu.edu phone: (401) 254-3208 snail mail: One Ferry Road Bristol, RI 02809 Dr Timothy J Osborn Climatic Research Unit School of Environmental Sciences, University of East Anglia Norwich NR4 7TJ, UK e-mail: t.osborn@uea.ac.uk phone: +44 1603 592089 fax: +44 1603 507784 web: [1]http://www.cru.uea.ac.uk/~timo/ sunclock: [2]http://www.cru.uea.ac.uk/~timo/sunclock.htm ______________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137 [3]http://www.evsc.virginia.edu/faculty/people/mann.shtml