date: Wed, 05 Jan 2000 11:21:09 +0200 from: Timothy Carter subject: Canberra decisions to: emilio@ppe.ufrj.br, rik.leemans@rivm.nl, lindam@ucar.edu, naki@iiasa.ac.at, barrie.pittock@dar.csiro.au, semenov@glasnet.ru, j.skea@psi.org.uk, roger.jones@dar.csiro.au, m.hulme@uea.ac.uk Dear colleagues, I set a 4 January cut-off for your comments on the annotated comments and on the general decisions reached in Canberra. This was primarily to ensure that we are all working with the same set of agreed actions when revising the text. The annotated comments will eventually have to be sent to the TSU, but we don't need to do this yet. I haven't received any suggestions for revisions on these (yet). However, Serguei has made some suggestions concerning the general decisions, which you should all have received yesterday. This is by means of a reply to Serguei and for all of you to note (so I don't have to send out a revised set of comments at this stage): Serguei's first point concerns palaeoclimatic analogues: < The proposed response: We will add a few references to illustrate cases where < palaeoanalogues have been developed for impact assessment, but we feel that the use of < analogues is more relevant for considering climate model validation (WG I) than for < constructing detailed climate scenarios for use in policy-related impact assessment ( cf. < F. Oldfield general comment and further justification below). Moreover, the use of < analogues is described at more length in Chapter 13/WG I report, which is devoted < exclusively to climate scenarios. < My comment: I disagree. As I definitely said in Canberra, there are two equally < solid and usable approaches at the moment: analogue and model ones (with all < respect to modelers). IPCC is not a proper place to judge which approach is < more solid, this should be decided through scientific discussions at SCIENTIFIC < conferences, in articles in leading scientific periodicals, etc. Professor < Andrew Velichko has just given me very interesting and detailed scenarios map < on future changes in vegetation in Europe. No principle differences with AOGCM < predictions were found be me. I think that interaction of these two approaches < will be mutually beneficial, and there is no need to vote within IPCC for ONE < of these approaches. I will strongly stay for methodological diversity. < Let me propose the following compromise version of our response: We will add a < short paragraph and few references to illustrate cases where palaeoanalogues < have been used for developing climate scenarios as well as respective impact < assessments. A reference to Chapter 13/WG I report, which is devoted < exclusively to climate scenarios, will be also made. I can live with this compromise decision as it sidesteps the contentious issue of the validity of the approach. However, we probably still have to address this issue somewhere (possibly in Chapter 13/WG I) since it is raised forcibly by Oldfield and less directly by Anisimov and Borzenkova (and Velichko). We may have to annotate relevant general reviewers' comments on the whole TAR (where the Oldfield comments appear), which we haven't yet done. I am still uncomfortable with the idea of using past reconstructed climate for "prediction", where the mechanisms for past changes (e.g. altered solar insolation) may be quite different from anticipated future changes (i.e. greenhouse gas forcing). I use the term "prediction" here to imply that they should offer plausible scenarios of the future. Can we accept that they are plausible simply on the grounds that they have occurred in the past? I concur with Oldfield that there are numerous examples of rapid warming events in the past that are difficult to explain and may be relevant as plausible scenarios for a future unstable climate response to rapid forcing. However, to my knowledge, I don't believe that past rapid warming events have been applied as scenarios in impact assessment. IPCC cannot easily review and evaluate scenarios that have not been developed and applied. On the other hand, I recognise that other palaoeanalogues have been widely applied in impact assessments and (appear) to give similar patterns of change as some AOGCMs in some regions (though I don't see that this is a sufficient argument for using them for prediction!) We can reference some of this work. However, perhaps we don't need to raise the issue of the validity (or otherwise) of paleaoanalogues here in the chapter, as this will be covered in Chapter 13/WG I. Note that we may include a Table from Chapter 13/WG I showing attributes of various scenario construction techniques, where there is some evaluation of the different methods. Serguei's second point: < Decision: The section on water resources will be revised to read marine and freshwater < scenarios. A new paragraph will be required on marine scenarios (we need to identify < someone to draft this). The section on freshwater could be shortened and reference made to < Chapter 4. Nigel Arnell, CLA for Ch 4, has been contacted to discuss this. < My comment: Basically I agree. However, let me finally clarify the point. I suggest to < retain a structure of the subsection as it is (Reference conditions, Methods of scenario < development, Application and interpretation…), but in addition to water resource scenarios < write something on marine scenarios and freshwater scenarios emphasizing environmental < aspects (e. g., pollution, acidification). OK, but we must try to keep this section concise! < Professor Alla Tsyban (CH6 CLA) can drafted 0.5 page on marine issues and Anne Koukhta < (who is already our CA) can take care on freshwater environmental issues (also 0.5 page). < Tim, please, respond, whether you are agreeable. This would be useful - can Prof Tsyban and Dr Koukhta take a global view on these issues? Again, we should be looking for a very brief mention of the issue. < In addition to Tim's contacts with Nigel Arnell I think I shall contact (if you do not < mind) with Igor Shiklomanov to get his opinion on our freshwater resource subsection (as < he is respective CLA in WGII). That's a good idea, as the tables that we currently have in the text are based on his work. I think that Arnell may also have contacted Prof. Shiklomanov. Finally, please remember that we have set ourselves a 21 January deadline for revised sections. Let's see if we can keep to this ambitious schedule. Best wishes and a Happy New Year to you all, Tim ************************************************ Dr. Timothy Carter Finnish Environment Institute Box 140, Kesäkatu 6, FIN-00251 Helsinki, FINLAND Tel: +358-9-40300-315; GSM +358-40-740-5403 Fax: +358-9-40300-390 Email: tim.carter@vyh.fi ************************************************