date: Thu, 21 Oct 2004 15:31:24 +0100 from: Sarah Raper subject: Re: [Fwd: 2004GL021238 Decision Letter] to: Tom Wigley --Apple-Mail-1--197200143 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Dear Tom, So its good news really on this one, but lots of things to cover re Jonathan. I have just reworked my calculations for a paper for GRL on glacier and ice cap volume and am just adding some details, its the one which says only 24 cm of SLR equivalent in GSICs. Will send it to you at the end of the weekend hopefully (then I have to do some IPCC drafting). I think you should see it before we resubmit this one... cheers, Sarah On 20 Oct 2004, at 14:48, Tom Wigley wrote: > > > -------- Original Message -------- > > Subject: > 2004GL021238 Decision Letter > > Date: > Tue, 19 Oct 2004 17:45:16 UT > > From: > grlonline@agu.org > > Reply-To: > lrinas@agu.org > > To: > wigley@ucar.edu > > > > > Dear Dr. Wigley: > > Thank you for submitting your manuscript, "Extended Scenarios for > Glacier Melt due to Anthropogenic Forcing," to Geophysical Research > Letters. Appended you will find two reviews. Based on these reviews, > I am unable to accept the paper for publication in GRL at this time; > however, a revised version of this paper that takes into account the > reviewers' comments should be of interest to our readers. > > Please include with your revised manuscript a statement indicating how > you have dealt with the review comments. List the comments > individually, explain how you responded to each comment, and provide > the location of the response within the manuscript (page and > paragraph). Should you choose not to make a change recommended by a > reviewer, please justify that decision. I will review your responses > and the revised manuscript before making a final decision on > publication. > > I would like to receive your revised paper as soon as possible. > Please submit a publication-ready copy of the manuscript by 2 November > 2004. When you are ready to submit your revision, use the following > link: > > el=A1K4BFnG2A6BHlO5I4A9ZzXQUHQ15tTFLnd9XQoGQAZ> > > I look forward to reading your revised manuscript. > > Sincerely, > > James E. Saiers > Editor, Geophysical Research Letters > ----------------------------------------------------------------------- > ------- > Reviewer Comments > > Reviewer #1 Evaluations: > Science Category: Science Category 2 > Presentation Category: Presentation Category B > Annotated Manuscript: No > Referrals: No > Highlight: No Preference > > Reviewer #1(Formal Review): > > Review of "Extended scenarios for glacier melt due to anthropogenic > forcing" by T M L Wigley and S C B Raper > > There is a practical need to be able to make projections of glacier > melt on the timescale of several centuries, because these timescales > are relevant to scenarios for stabilisation of atmospheric > greenhouse-gas concentrations. This letter makes a proposal which > could be of immediate practical use on these grounds and therefore > potentially Category 1. However I would assign it to Category 2 in its > current form because I think the *scientific* nature of the > improvement relative to the "old" scheme and its use on these longer > timescales needs to be better justified in order for one to be > confident in using it. I would put it in presentation category B as > there are some corrections and clarifications that would be useful to > make. The general layout and choice of diagrams are good and the > abstract is a good summary. > > Unfortunately there was very little space in the TAR to describe the > method being used, which was derived from the work of Van de Wal and > Wild, as the authors say. The TAR method also used area-volume > scaling, as in section 2, with an exponent of 0.72. The scaling was > applied to ensembles of glaciers of various sizes, for each of the > glacierised regions, from the inventory of Van de Wal and Wild, rather > than being applied to the global totals of volume and area, as in the > present paper. The TAR scheme was simply a fit to the results, done > for convenience in order to be able to interpolate and extrapolate. It > might help the reader to state that the TAR scheme is also addressing > the same point, that the global mass balance sensitivity decreases > because the glacier area decreases. I know that something like this is > said at the end of the para at the foot of p2, > but in the subsequent discussion I think the reader might forget this > and from the start of section 2 might assume that the new scheme is > different in principle from the "empirical correction", although they > have the same motivation in representing the way that the global > glacier area and volume behave. > > I believe that the present paper is suggesting a different way to fit > the results of the TAR computations for the early period, in effect, > since it uses the relation between alpha and gs(1990) from the TAR. I > am not certain I'm right, however, and therefore would suggest that it > could be stated more clearly what the relationship is between the > schemes. It is certainly interesting that they are close together up > to 2100. The proposed new fit is the global scaling relationship. It > is a good idea to try this, but some comment might be in order about > whether you'd expect it to work. The scaling relationships apply to > *individual* ice masses, and if you look at it analytically you > wouldn't expect the same (or any) power-law scaling to apply to the > sums of the areas and volumes, would you? > > Secondly, I think more should be said on whether it is justifiable to > use any such scheme when a significant proportion of the total mass > has been lost. The reason is the final caveat on p11. Mass will be > lost preferentially at low altitude, and a hypsometric scheme with > dynamics is needed to model this properly. It is clear that the > empirical scheme used in the TAR is invalid for large changes, but is > it clear that the scaling law is valid? The argument on timescales is > also maybe open to question. There may be an implication on p12 that > one can go to 2400 because the timescale calculated on p6 is ~800 > years. But this timescale is the time for melting all the ice at the > 1990 rate. Rates get much larger in the future, as your results show. > 800 years is probably a lot longer than the dynamic response timescale > for most glaciers. > > Minor comments > > p2 2nd para and elsewhere. The TAR chapter is Church et al. (2001) and > all the lead authors should be listed, as requested by the IPCC, not > just the coordinating LAs. > > p4 sect 2 1st para and p7 eqn 13. I think beta is a mass balance > sensitivity, so isn't beta=1/T dgs/dt rather than dgs/dT? Beta0 is the > initial sensitivity, I guess. Is beta0=alpha? In transforming eqn 1 to > eqn 4, alpha has vanished without comment. It might be clearer to say > (beta(t)/beta0) = (A0-A)/A0, rather than writing a proportionality. > > p4 eqn 3. I was a slightly put off by the different use of [] in the > two formulae. Why not [(V0-V)/V0]^n in the first one too? > > p4 bottom. "As becomes clear below". Where do we return to the > discussion of n? I can't find it. Having started with n=0.82, on p5 we > change to n=1 and it is not clear to me which value of n is used in > the computations. > > p6 just before eqn 10. Do you have a ref for T(1990)=0.65 degC? > > p6 eqn 11. You could point out that this is just a constant rate of > loss forever. > > p9 2nd para. The TAR calculations do have an initial ice volume. Do > you mean that neglect of the *uncertainty* in this is unimportant? > > Fig 3. I'm not sure which lines are temperature and which sea level. > > > > Reviewer #2 Evaluations: > Science Category: Please choose one > Presentation Category: Please choose one > Annotated Manuscript: No > Referrals: No > Highlight: No Preference > > Reviewer #2(Formal Review): > > Accept with minor revisions > > Science Category 1 Innovative research with interdisciplinary/ etc. > > Presentation Category A > > Comments > > This is an important piece of research which extends the period over > which we can make quantitative predictions of the magnitude of > global-sea-level rise. In terms of the upcoming IPCC AR4, it is > especially timely. > > Suggested Minor Revisions > > Page 3, First para -- state time period of projections > Page 3, last para "is almost certainly greater than this" -- link to > latter estimates. > Page 4, Define V > Page 6 time scales are short or long, not small or large. > Page 7 suggest numbering or bulleting the three conditions to make > clearer. > Page 8 Change "this figure" to "Figure 1". > Page 16 onwards -- all figures and captions should be reviewed to make > as clear as possible to a general audience, as I am sure this paper > will > be used by climate impacts scientists, as well as climate change > scientists. Figure 1 is fairly clear, but Figure 2 has a number of > lines > -- can this be made clearer? Figure 3 needs most work. Suggest left y > axis be labelled GSIC melt and right y axis be labelled Temperature -- > as presented could accidently interpret a 45oC rise! Also review > caption. > > > > > > ----------------IMPORTANT LINKS TO GRL > INFORMATION------------------------------ > > To ensure prompt publication: > > 1. Follow file format guidelines > 2. Provide a color option > 3. Limit character count of total manuscript to <25,600 characters and > spaces, > including text, figures, tables, and equations > 4. Combine figure parts or provide separate captions > 5. Sign and send the (1) publications option form and (2) copyright > transfer agreement > > For information on all of the above items, see Tools for Authors at > http://www.agu.org/pubs/inf4aus.html. If you have any questions, reply > to this e-mail. > > A manuscript tracking tool is available for you to retrieve the status > of > your article after acceptance: > http://www.agu.org/cgi-bin/ms_status/ms_status.cgi > > You can download a free version of Adobe Acrobat Reader at > http://www.adobe.com/products/acrobat/readstep2.html > > > >