cc: m.hulme@uea.ac.uk, parryml@aol.com, steve smith , s.raper@uea.ac.uk, Tsuneyuki MORITA , tim.carter@fmi.fi date: Mon, 27 Aug 2001 14:16:16 -0600 from: Tom Wigley subject: Re: TGCIA scenario recommendations to: Rob Swart Rob Swart wrote: > > Dear Tom, > > Thanks for your message and papers. The problem is clearly one of the > science-policy interface. If science cannot demonstrate that it makes a > difference in terms of avoided climate change and impacts if GHG > concentrations are stabilised, why bother? I'M SURE THAT THIS IS JUST A RHETORICAL QUESTION -- BUT HERE IS A SIMPLE ANSWER NEVERTHELESS. IT IS LIKE DRIVING A HEAVY CAR WITH POOR BRAKES DOWN AN UNFAMILIAR ROAD IN MOUNTAINOUS TERRAIN. THERE MAY BE NOTHING SERIOUS IN SIGHT, BUT SOME FINITE (BUT POORLY DEFINED) PROBABILITY OF A ROCK FALL OR CLIFF OR OTHER DANGER OUT OF SIGHT. SINCE THE CAR HAS LARGE INERTIA, IF WE PUT THE BRAKES ON, WE WILL NOT SEE A RAPID RESPONSE. THE TRICKY QUESTION IS JUST WHEN AND HOW HARD TO PUT THE BRAKES ON. Currently a Danish guy, Björn > Lomborg, is making the headlines again (Guardian, New York Times, > Economist), TV programmes, etc.) telling the public (and policymakers) not > only that there aren;'t any environmental problems, but also, even if > climate change may be real, it does not make any sense at all to do > something about it, since efforts to control GHG emissions are expensive > and the mitigation would not make any difference at all anyway in terms of > avoiding negative consequences. Very popular message. AND A MUCH MORE COMMON ONE HERE IN THE USA. DIFFICULT TO DEAL WITH. Now clearly, > scientists should clearly explain what they can say about this issue. My > expectation would indeed be that comparing climate changes resulting from > reference cases and from stabilization cases would not be distinguishable > until well into the 2nd half of the century (like in the GRL paper), but if > this is so, so be it. YES -- BUT A LOT OF PEOPLE DON'T EVEN REALIZE THIS. 2050 seems a lot closer now in 2001 (2050 is THIS > century and our childrens' lifetime) than it was in 1999 (when 2050 was > something of the next century and some abstract next generations). It is a > matter of communication skills to get the message across about the long > timescales and inertia of the systems involved, and the difficulty of > identifying the climate change signal in the noise of natural variability. OF COURSE -- HAVEN'T WE BEEN SAYING THIS FOR YEARS? I CERTAINLY HAVE. UNFORTUNATELY, THE MESSAGE DOESN'T GET ACROSS TO THE RIGHT PEOPLE. > I would be curious what your opinion is about the UK work of Nigel Arnell, > Martin Parry, John Mitchell and others, analysing the (significant) avoided > impacts of 550 stabilisation from an IS98a reference. I PRESUME YOU MEAN IS92a, NOT IS98a. I HAVE NOT SEEN THIS WORK, BUT I NOTE FOUR THINGS: (1) NONE OF THESE THREE PEOPLE ARE ECONOMISTS; (2) IF THIS IS BASED IN ANY WAY ON THE HADLEY CTR'S GRL PAPER ON STABILIZATION, THEN IT IS LIKELY TO BE FLAWED BECAUSE THE CALCULATIONS IN THAT PAPER WERE TOO IDEALIZED; (3) MY OWN WORK COMES TO A DIFFERENT CONCLUSION; (4) THE ISSUE IN ANY EVENT IS COST OF MITIGATION VERSUS BENEFITS OF REDUCED CLIMATE CHANGE. Another strategy of > concerned scientists may be not to do these analyses at all in order to > avoid a possible result that the differences between reference and > stabilisation can not be demonstrated in a scientifically credible and > unambiguous way and hence climate policy action may be obstructed. To me, > this does not seem to be the honest way to go. I AGREE COMPLETELY. EVEN IF SOME PEOPLE COP OUT, *SOMEONE* WILL DO THE WORK. IT JUST HAS TO BE CAREFULLY PACKAGED. > > I am not sure what this all implies for the planned recommended > stabilization runs. Your points about the climate sensitivity and non-CO2 > gases are well taken. I am not sure the sulfur emissions in the proposed > post-SRES scenarios would make a lot of difference, since already in the > SRES base cases sulfur emissions are pretty low, and these would only be > slightly different (usually lower) in the stabilisation cases. THE RESULTS I USED IN THE STABILIZATION PREPRINT PAPER USED MiniCAM TO ESTIMATE THE CONCOMITANT EFFECTS ON SO2 OF CO2 STABILIZATION AT 550ppm. ARE YOU SAYING THAT MiniCAM IS RADICALLY WRONG? I DOUBT IT. OF COURSE, THIS SHOULD BE (AND I BELIEVE IS BEING) DONE WITH A BUNCH OF MODELS; BUT I AM WILLING TO BET THAT MY RESULTS ARE QUALITATIVELY CORRECT. You suggest > "carefully constructed idealized scenarios". Do you mean carefully > constructed from the climate system point of view in order to get > "distinguishable results", or carefully constructed from the socio-economic > point of view so as to analyse real-world consistent and plausible futures > (the latter is what Morita's exercise tried to achieve)? My answer would > be: both. YES -- THAT IS EXACTLY MY POINT. FROM WHAT I CAN SEE (AND MY APOLOGIES IF THIS IS WRONG) NOT ENOUGH CLIMATE EXPERTISE HAS GONE INTO THE ECONOMIC WORK SO FAR -- I AM ARGUING FOR BETTER COMMUNICATION. > > I'd like to reflect a little bit more on this and since I am a scenario > expert rather than a climate expert, await reactions from people more > expert in the area of climate modelling, like Sarah, Mike and Tim, and > Martin himself as chair of the TGCIA. MANY THANKS FOR THIS QUICK RESPONSE. THESE ARE DIFFICULT ISSUES. > > Thanks again, > > Rob > > > Tom Wigley > > edu> cc: parryml@aol.com, tim.carter@fmi.fi, m.hulme@uea.ac.uk, > s.raper@uea.ac.uk, Tsuneyuki MORITA , steve smith > 25-08-01 , (bcc: Rob Swart/RIVM/NL) > 01:47 Subject: Re: TGCIA scenario recommendations > Please > respond to > wigley > > > > Rob and others, > > The key thing with doing stabilization runs with AOGCMs is (as Rob says) > that the different cases "would have to be distinguishable from one > another". This is the crux of the problem (in fact, it is a non-trivial > problem even to define what is meant by "distinguishable from one > another"). > > A few years ago we decided to try to do some matched no-climate-policy > and (550ppm) stabilization runs where the two scenarios had some > semblance of realism. (It turns out that the only similar work is that > done by the Hadley Ctr, but the scenarios they used are highly > idealized.) Our runs were also idealized in that we only changed CO2 -- > in the best scientific tradition of changing only one thing at a time to > assess sensitivities. The first results of our exercise (using CSM) are > in Dai et al., J. Climate 14, 485-519, 2000. A number of things were > clear from this. First, one cannot tell much from single realizations of > the two cases -- ensemble runs are essential. Second, as we already knew > from running simple models, the no-policy and stabilization runs diverge > only slowly. Even after 50 years, the two are only just distinguishable > at the global-mean level; so, clearly,differences at the regional level > (especially for precipitation) would not be detectible above the noise > of natural variability. > > So our next step was to do ensembles of 5, this time using PCM instead > of CSM (this paper is in press in BAMS -- for a pdf preprint, look at > www.cgd.ucar.edu/cas/adai/). Even then, for ensemble means, the > separation between the no-policy and stabilization cases is slow. So I > devised an extended no-policy case out to 2200 (50 years beyond where > the CO2 level stabilizes in the stabilization run), and we extended some > of the runs out to 2200. This work is in press in GRL (and downloadable > from the above site). Additional important results come from these > experiments. One important result is that, even for precipitation, the > *patterns* of change are not detectibly different between the no-policy > and stabilization runs. A second important result is that, for most of > the world the intra-ensemble differences are similar to or greater than > the underlying signals of change. Distinguishing the no-policy and > stabilization runs therefore presents a much greater challenge than any > of you probably realize. > > There are two issues to keep in mind, however. The first is that PCM and > CSM have quite low climate sensitivities. So, will things be different > if one used a more sensitive model? I suspect not in any major way. The > reason is because inter-annual variability tends to be higher in more > sensitive models, so the signal-to-noise ratio may not change much. This > also applies to the intra-ensemble noise, since the root cause of these > intra-ensemble differences is the internal variability of the model. > > The second issue is that we have only changed CO2 in our experiments. We > know that attempts to stabilize CO2 via emissions reductions also affect > SO2 emissions -- so perhaps the no-policy and stabilization cases might > be more distinguishable if one accounted for these concomitant SO2 > effects? I have addressed this issue at the global-mean level in a paper > on stabilization that I will attach to this email. (A more extensive > analysis is in another paper, with Steve Smith as my co-author, that I > am not ready to share with anyone just yet.) My judgment, as someone > with quite a lot of experience in this area, is that having full spatial > details will not make the problem any easier; since, as the spatial > scale is reduced so the noise increases. > > My recommendation from all this is that, first, you read the attached > paper (and I would welcome feedback on this) and the three > above-mentioned Dai et al. paper. Then, you might want to re-consider > what your strategy should be. In my view, I do not think we as a > community are at the stage where we can blindly develop paired no-policy > and stabilization scenarios and simply feed them into AOGCMs to see the > consequences. I believe that carefully constructed idealized scenarios > (perhaps based on what Morita is doing) will provide much more useful > information. You are already probably well aware of the need to do > ensemble runs, and I don't need to remind you how computationally > expensive this can be. > > I hope these comments, and the papers, are useful. I'm sorry that it is > impossible for me to come to the Barbados meeting, but I am willing to > help in any way that I can. > > Best wishes (and good luck), Tom. > ******************************** > > Rob Swart wrote: > > > > Dear Sarah, Tom, Tsuneyuki, Martin, Mike and Tim, > > > > Back from holidays I found your email exchange. Let me first apologize > that > > I did not inform Sarah about this TGCIA action. I remembered from the > > IPCC-TGCIA meeting ? apparently wrongly - that Mike and/or Tim would > inform > > Sarah, as they would be in touch with her anyway (I did not even have > > Sarah's email address at the time). Let me also reiterate the reason for > > Tsuneyuki's invited proposal. In order to have comparable GCM results > > available and impact studies based on these results at the time of the > IPCC > > Fourth Assessment Report, and taking into account that GCM teams are > > unlikely to perform dozens of runs, the IPCC-TGCIA (chaired by Martin) > > intends to recommend a limited set of both baseline and stabilization > > scenarios for such runs. In this way, impact modellers in the coming > years > > could base their analysis on different runs from different GCMs for the > > same socio-economic scenario(s). Evidently, teams are free to run > whatever > > scenario they think interesting, but comparability would be preferable, > and > > many teams have proven responsive to IPCC-TGCIA recommendations in the > past > > as I understand it. > > > > The TGCIA has reached agreement on which 4 of the 40 SRES baseline > > scenarios would be most interesting (see meeting report: 4 scenarios > (A1FI, > > A2, B1 and B2) for 3 time periods 2020s, 2050s and 2080s). The next > > question was: since a (maybe "the") core policy question is what the > > benefits (or avoided impacts) would be of stabilizing GHG concentrations > at > > various levels, and since impact analysis should be based directly on GCM > > results rather than on results from simple climate models/IA models, it > > would be useful to also recommend a limited set of stabilization cases. > To > > make this a sensible effort, all the cases would have to be > distinguishable > > from one another from a GCM viewpoint. This may allow for combining > various > > scenarios which may be very different socio-economically, but would give > > very similar climate results for this century, such as the B1 and 550, > and > > the 650 and B2 cases. The stabilization cases would be selected from the > > following table, of which the cells contain available (post-SRES) > scenario > > runs: > > |-------------+-------------+-------------+-------------+-------------| > > | |450 ppm |550 ppm |650 ppm |750 ppm | > > |-------------+-------------+-------------+-------------+-------------| > > |A1T | | | | | > > |-------------+-------------+-------------+-------------+-------------| > > |A1B | | | | | > > |-------------+-------------+-------------+-------------+-------------| > > |A1FI | | | | | > > |-------------+-------------+-------------+-------------+-------------| > > |A2 | | | | | > > |-------------+-------------+-------------+-------------+-------------| > > |B1 | | | | | > > |-------------+-------------+-------------+-------------+-------------| > > |B2 | | | | | > > |-------------+-------------+-------------+-------------+-------------| > > > > It was suggested to select 2-4 cases from the more than 70 scenarios runs > > in the post-SRES programme co-ordinated by Tsuneyuki. Tom, it may well be > > that your "post-WRE" work serves the same purpose, but the rationale for > > selecting post-SRES cases would be: consistency with the SRES narratives > > and numbers of the IPCC, and the much-acclaimed multi-model > characteristics > > of the (post-)SRES work. To downsize the 70-odd cases to 2-4 cases and > not > > burden Sarah too much, it was suggested to have one model (MAGICC) run a > > subset of some 10-15 cases which seemed to make sense. Please also note > > that not all 70-odd cases are useable, either because they do not have > all > > relevant GHG gases, or there have been questions about the > > consistency/quality of their assumptions, e.g. a correct simulation of > the > > SRES base case by teams participating in post-SRES but not in SRES > (right, > > Tsuneyuki?). More importantly, Tsuneyuki used his intimate knowledge of > all > > cases and their distribution over base cases and stabilization levels to > > recommend 13 cases. This selection was discussed with me and Naki during > a > > brief meeting in Washington in June and seemed to be a very appropriate > > one. > > > > I noted the remark by Sarah that mean climate change results would be > > rather be model-independent (for a given climate sensitivity), while > > Tsuneyuki notes the large differences in the post-SRES work. These > > differences may not have to do with different approaches with respect to > > the carbon cycle or radiative forcing calculations, but rather with the > > freedom modellers had (or rather: took) in selecting the time path > (beyond > > 2100) towards stabilization/time horizon, and the changes in emissions of > > non-CO2 GHG in the stabilization analyses which focused primarily on CO2 > > stabilization. This would need to be clarified in detail for the runs to > be > > selected, and I suggest that only those runs are further used for which > the > > authors provide sufficient information on these issues. > > > > Concluding, I would like to ask Sarah, if she would be willing to take > the > > material provided by Tsuneyuki and perform the required calculations for > > the 13 cases (radiative forcing, global mean temperature and sea level > > rise, right, Mike/Tim?) within the next 1-2 months. The results would be > > discussed electronically in a small group (the addressees of this > message) > > in October/November and a preliminary proposal based on these discussions > > would be the input for a discussion on this issue during the next TGCIA > > meeting in Barbados, in November. Tom's recent work may be useful for > this > > discussion as well, and I wonder if the mentioned (draft) papers could be > > distributed to this group or even the full TGCIA. > > > > Kind regards, > > > > Rob > > > > Dr. Rob Swart > > Head, Technical Support Unit > > Intergovernmental Panel on Climate Change Working Group III: Mitigation > > P.O. Box 1 > > 3720 BA Bilthoven > > Netherlands > > tel. 31-30-2743026 > > fax. 31-30-2744464 > > email: rob.swart@rivm.nl > > ------------------------------------------------------------------------ > Name: ASPEN1.DOC > ASPEN1.DOC Type: WINWORD File (application/msword) > Encoding: base64 > > Name: 10-NONC.XLS > 10-NONC.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 11-TRUEC.XLS > 11-TRUEC.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 12-QCH4.XLS > 12-QCH4.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 13-REACT.XLS > 13-REACT.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 14-QSO2.XLS > 14-QSO2.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 15-TSO2.XLS > 15-TSO2.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 1-FOSS.XLS > 1-FOSS.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 2-DEFOR.XLS > 2-DEFOR.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 3-CO2.XLS > 3-CO2.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 4-CEQUIV.XLS > 4-CEQUIV.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 5-PROFIL.XLS > 5-PROFIL.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 6-EMS.XLS > 6-EMS.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 7-PATHS.XLS > 7-PATHS.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 8-550EMS.XLS > 8-550EMS.XLS Type: EXCEL File (application/msexcel) > Encoding: base64 > > Name: 9-550TEM.XLS > 9-550TEM.XLS Type: EXCEL File (application/msexcel) > Encoding: base64