date: Fri, 8 Sep 2006 20:52:08 +0200 from: Dominique Raynaud subject: Re: [Wg1-ar4-ch06] Latest version of the Chap 6 Executive Summary to: Jonathan Overpeck , IPCC Chapter 6 Dear Peck and ch.6 LA's I propose two modifications: page 6-1 lines 15 to 19 and page 6-3, line 35. They are highlighted in cyan color. The purpose is to make sure that we highlight that greenhouse gases very likely have played a major role in the amplification process. Have all a nice week end Dominique Hi Chapter 6 LA's: Please review the attached latest version of the chapter 6 executive summary. As before, changes have only been made for the purpose of clarification - thank you to those who provided feedback. Most changes (highlighted in yellow) are quite minor, however a couple warrant some highlighting to make sure we have the optimal final wording: 1) the glacial bullet was debated by a couple team members and we decided that the bullet needed to be more specific. For example, the use of the terms early and mid-Holocene wasn't precise. So, how do you like: o Glaciers of several mountain regions of the Northern Hemisphere retreated in response to orbitally-forced regional warmth between 11,000 and 5000 years ago, and were smaller at times prior to 5,000 years ago than at the end of 20th century, or were even absent. Note that this formulation also manages to get in the role of orbital forcing and the fact that this orbital forcing caused regional, as opposed to hemispheric or global, temperature anomalies. The revised bullet is also now more consistent with the glacial box figure in terms of years cited. Ok? 2) Fortunat came up with the magic bullet (we think) describing the climatic implications of the recent pre-industrial trace gas changes when he suggested: The small preindustrial greenhouse gas variations also provide indirect evidence for a limited range of decade- to century-scale variations in global temperature. Sound ok to all? 3) Fortunat also queried regarding the why Europe, Asia and Australia were not included along with parts of Africa and North America in the drought of the last 2000 bullet. The reason for not including this other regions is that we don't have much evidence for recurrent droughts lasting decades or longer in these other regions. They may have happened, but the literature is apparently not well developed in this regard. Thus, without the backup in the main text, we can't expand the bullet to include more regions. No reviewers in any review cycle provided insights to change this assessment, so we feel it's better to leave as it is. Also, it would be a substantive change to include them at this stage - another reason to leave as is. Ok? 4) Then there is the tricky bullet on the amplification of orbital forcing. We appreciate the debate on this one and suggest we go with the following: Changes in greenhouse gas concentrations, ice sheet growth and decay, ocean circulation and sea ice changes, biophysical feedbacks, and aerosol (dust) loading have very likely influenced this amplification. Note that the use of "influenced this amplification" (the "amplification" is a main topic of the bullet - don't want to lose it) helps clarify that some of the listed factors may have reduced the amplifications, some increased. Also, it makes the use of the term "very likely" more sound - hard to imagine the factors listed played no roles. Is this ok? Again, many thanks for your input. Please note that we're close to having a CLA edited (and shortened as necessary) complete final draft, and plan to circulate this early next week for FAST final checking. Please set aside time so that you can read and suggest final edits within 24 hours of receipt. Best, Peck and Eystein -- Jonathan T. Overpeck Director, Institute for the Study of Planet Earth Professor, Department of Geosciences Professor, Department of Atmospheric Sciences Mail and Fedex Address: Institute for the Study of Planet Earth 715 N. Park Ave. 2nd Floor University of Arizona Tucson, AZ 85721 direct tel: +1 520 622-9065 fax: +1 520 792-8795 http://www.geo.arizona.edu/ http://www.ispe.arizona.edu/ Attachment converted: Macintosh HD:Ch06_FinalDraft_ExecSumV6.doc (W8BN/MSWD) (000F366B) _______________________________________________ Wg1-ar4-ch06 mailing list Wg1-ar4-ch06@joss.ucar.edu http://lists.joss.ucar.edu/mailman/listinfo/wg1-ar4-ch06 Attachment Converted: "c:\eudora\attach\_Ch06_FinalDraft_Exec#F3CC4.doc" Content-Type: text/plain; charset="iso-8859-1" X-MIME-Autoconverted: from 8bit to quoted-printable by joss.ucar.edu id k88IqJBO025529 -- Dominique Raynaud Research Director at CNRS Laboratoire de Glaciologie et Géophysique de l'Environnement BP 96 38402 Saint Martin d'Heres Cedex, France raynaud@lgge.obs.ujf-grenoble.fr PH: +33 4 76 82 42 52 FAX: +33 4 76 82 42 01 _______________________________________________ Wg1-ar4-ch06 mailing list Wg1-ar4-ch06@joss.ucar.edu http://lists.joss.ucar.edu/mailman/listinfo/wg1-ar4-ch06