cc: tar_cla@earth.usgcrp.gov, tar_la@earth.usgcrp.gov, wgii.bureau@earth.usgcrp.gov, tar_reved@earth.usgcrp.gov, ipcc@earth.usgcrp.gov, ipcc@usgcrp.gov date: Sun, 24 Sep 2000 10:06:38 -0700 (PDT) from: Stephen H Schneider subject: Re: TS - PLEASE REVIEW! to: Neil Leary Hello all. My TS reiview is below. I look forward to the next draft and thank the drafters for their hard work!! Cheers, Steve ------ TS FGR 1st Draft Review by Stephen Schneider General: Like the SPM, it just keeps getting better. Please be sure any comments of any of us on the SPM that are accepted are also reflected in the TS as I and likely others may not repeat them here if we made them for the SPM. TS Reviewer: Stephen Schneider Pg 11, line 2: A change in the bottom line from 0.7 to 3.5 to 1.3 to 4.9 is hardly "somewhat higher"! This is a dramatic change as many took the reduction in the SAR by a smaller percentage--due to aerosol scenarios--as a major revision. Let's avoid hard to interpret words like "somewhat" and just give facts: say "estimated warming is about 50-100% higher than..." This is a very improtant issue and we need to discuss it if there are strong feelings, but by giving the range we avoid such contentious arguments. TS Reviewer: Stephen Schneider pg 11; lns28-30: Is this language confusing the WG1 "likehood" with the wg2 CONFIDENCE? TS Reviewer: Stephen Schneider pg 11; ln39: Once again the myuthical and hard to define "rapid shutdown" is given for the THC. Why not just "a substantial weakening"--say 50% reduction or more. In that case the confidence rating is medium as at least one third of the studies have a significant THC decrease by 2100, and we don't mislead people by picking a full collapse--a somewhat arbitrary concept given the high spatial heterogeniety in deep water formation anyway--in some distant century and duck out from the tough question of what might happen in this century for some rapid CO2 buildup scenarios and in some models. Let's not fear the type 1 error so much we let society alone worry about the type 2. And, as written it is not telling policy makers all we know about this difficult topic TS Reviewer: Stephen Schneider Page 11, footnote: the confidence/likelihood issue again. Isn't the 99% thing a "likelihood scale' as we agreed with WG1, and only to be applied when real frequentist information--data--is available, but that we use confidence scale when there are judgments embedded. Either way, first "likely" needs a strong word in front of it like "exceedingly" or replace it with "virtually certain", since it is 99% case--best is to use what WG 1 is using for this top 1% likelihood category--if we are going to use the likelohood scale at all in WG2. TS Reviewer: Stephen Schneider pg 12; lns 47-45: It is not the job of WG2 to assess the likelihood of climate scenarios being true, and we are to avoid cascade statements. Yet there are statements about being "definitive"--what ever that means statistically-- about attribution to human induced climate. This must be reworded to reflect whether the evnets are significant locally--that is whether local climate changes can be confidently associated with local hydrological changes. The most we can responsibly say about attribution is whether observed hydrological changes are consistent with most scenarios of anthropogenic climate change, and even that is tough to do without a comprehensive set of such projections available to test against. If there were a robust conclusion about warming effects on hydrology maybe we cousl say something stronger, but given the usual lower confidences applied to precipitation forecasts by WG 1, I don't think we can attribute competently. On lines 50 and lines 53 the same problem occurs. This MUST be revised to eliminate any strong claims about attribution to human induced climate change as that is not our charge and we didn't have a fully vetted debate on it. TS Reviewer: Stephen Schneider pg 14; lns 28-29: Given the conditional word "can" it makes the very high confidence a bit silly given that the statement is pretty obvious. I'd consider dropping any confidence level here. TS Reviewer: Stephen Schneider pg 15; ln 12: Again a conditional word like "could" renders the medium confidence redundant, for if we knew nothing than this statement would have a 50% chance of being true as written. Think about dropping the confidence level for this if the wording stays as is. TS Reviewer: Stephen Schneider pg 15; lns 27-28: This statement about increased interannual variability and benefits/risks is too sweeping, since what kinds of variability are not specified and it is not adding anything to make vague and partially true statements when some kinds of variability changes coud make all impacts better--or worse--.If there is some major block of assessment information behind this statement better to summarize it briefly and specifically than to have a meaningless truism that is unclear as a placeholder. TS Reviewer: Stephen Schneider pg 15; ln 42: Replace "other" with "many" as climate also shapes ecosystem services. Or better perhaps, is simply to add to the sentence at the beginning--line 40-- after "impacts" the words "of climate change" and them you can keep the word "other". TS Reviewer: Stephen Schneider pg 16; ln 36: It seems pretty likely to me that habits rendered"unsuitable for many target species" woulld have lower adaptability--maybe this is a med-high confid to be sure nobody thinks we think it is less than an even bet? TS Reviewer: Stephen Schneider pg 17; ln 15: Most readers will not understand that the restriction of equilibrium assumptions renders nearly all conclusions much less than highly confident. Thus any seemingly highly confident conclusions based on such studies--even with a caveat sentence following--are too easy to misinterpret of misquote. Thus I'd attac a "medium confidence" to this statement so it can't be misquoted except by those with the gall to drop the confidence level at the end. TS Reviewer: Stephen Schneider pg 20; lns 36-44: In the discussion of Table 3, and the table itself, some indication of the kinds of climate change scenarios used to construct would be helpful--i.e., it was based on 2xCO2 studies from a variety of GCMs etc. Be sure that cascades are eliminated to the extent possible in assigning confidneces, by making the scenarios used more explicit. TS Reviewer: Stephen Schneider pg 23; ln 27: Is it really less than one chance in three that this would occur? That is what low confidence means. Maybe you want to assign a qualitative staet-of-science indicator like "competing explanations "here by stitching that phrase into the sentence and dropping the confidence level at the end. TS Reviewer: Stephen Schneider pg 23; ln 37: we can't know the number of malnourished to 3 significant figures. Better to give a range reflecting the literature--like 500,000 to 1,000,000--or whatever range is justified. Such a precise number as 790 won't seem credible. TS Reviewer: Stephen Schneider [Sorry, I have not had time to read all the regional sections in detail, but please note my many comments on the regional table for the SPM and be sure that if any of those comments are accepted the changes are reflected both here and in the chapter texts as well--thanks] pg 40; lns 41-48: It is gratifying to see that after so many rounds of revison this statemnt seems balanced and will have both credibility and influence. Good job drafters! (by the way, check to be sure the 90% number is still right since more work has been done on this over the past few weeks I understand) TS Reviewer: Stephen Schneider pg 41; ln: USE MORE "ipcc-LIKE LANGUAGE: replace "result in us having" with "lead to" or something like that. TS Reviewer: Stephen Schneider Page 8; ln 8: As I discussed in the SPM comment extensively, I think the "four lines of evidence" are really better described as " four categories of impacts". Also add the word "monetary" between "aggregate" and "impacts" wherever used--as argued in my SPM comments in detail. TS Reviewer: Stephen Schneider Page 41, footnote 3: I know words like "small" moderate" or large are arbitrary and somewhat normative--depends on what system you are looking at. I also know we need some categorization. I guess I have a bit of a problem with 2 deg C being a "small" change, given that it is as large or larger than any global changes over the Holocene epoch in which human civilization evolved. I guess for me one degree fits the small category--despite loss of some unique and valuable systems as the Chapt 19 authors responsibly point out--but two degrees is getting more than modetate given we have no experience with it, just questionalble models of its impacts. Maybe 1.5 is a better cutoff for the small/moderate boundary--and 1.5 is the lower range limit for climate sensitivity so not an unfamilar number in the literature. The best would be wholly non-normative words, like precedented for small, but I have a hard time finding them for the other categories. I guess I can live with this given you've defined what you mean by each--a definitation that might get lost by quoters of the draft--but have the most trouble believing 2 deg C is some how "small" given that empirical evidence for such a sustained global change is about zero for the Holocene conditions--and cross sectional studies do not qualify as empirical evidence in my book forthe transient changes that the real earth will undergo. TS Reviewer: Stephen Schneider pg 42; ln 9: "aggregate monetary impacts" again, add the middle word please. TS Reviewer: Stephen Schneider pg 42; ln 15: How can the confidence be low in a statement with a "could" in it? I think you are referring to the poor state of the science--so maybe best to put a "speculative" or "competing explanations" phrase in the text and to drop the confidence parenthesis at the end? TS Reviewer: Stephen Schneider pg 19; ln 42: To prevent misunderstanding that this refers only to market estimates, please add "Aggregate monetary" before "global economic welfare".TS Reviewer: Stephen Schneider pg 42; ln 48-50: This sentence refers to best guesses based on very uncertain state of science with competing explanations. As I've long argued, isn't it better to give a range of what is in the literature with some short caveats on the conclusions. Or how about the following to make the redrafting easier: "Even a small temperature incerase...(med confid), but could have net positive impacts..." That way it is qualified in the sentence and you wouldn't need the confidence parenthesis at all? Most important is not to convey more understanding than we have or to let naive readers take a best guess statement embedded in a wide range out of context and I'm not sure a medium confience at the end is enough to do that. TS Reviewer: Stephen Schneider pg 43; lns 19-20: Also might mention transients are harder to predict and thus foresight is lost along with adaptive capacity. TS Reviewer: Stephen Schneider pg 44; lns 29-31: This important warning about the THC weakening needs to be reflected in the table--why I have long opposed useing a full shutdown as the table enrty event--it triviliazes the issue and ducks the medium confidnece in substantial partial shutdowns even in this century--with potential for catastrophic shutdowns in later cneturies--a point made in footnote in table. TS Reviewer: Stephen Schneider Table 2: Please see my SPM comments as they apply here as well--and the need to replace the "rapid shutdown" phrase with "substantial weakening' and to assign that a low to med confidence needs to be discussed. We do not have to reflect the type 1 error proneness of WG1 as our task is impacts and if we have concerns about type 2 errors and partial THC shutdowns than there is no reason we can't put that in as long as the confidence we assign to it is not inconsistent with WG 1 language in their chapters--and I'm am fairly confident we can defend a L-M confidence for a substantial weakening for THC in 21st century. We need to discuss this if there is disagreement, and can't just ignore it because the draft is due in two weeks--too important. TS Reviewer: Stephen Schneider Table 3: How did you get a less than 5% chance (IE< very low confidnece) for fires? If you mean poor state of science, say that, but the idea of only a 5% chance here seems way off? TS Reviewer: Stephen Schneider Table 11: Too much precision on tourism receipts--need a footnote or text comments on why so many significant figures--is it possible to know it to this degree of precision? TS Reviewer: Stephen Schneider Figure 8: See earlier and SPM disucssion about lines of evidence versus categories of impacts and to put "monetary" between aggregate and impacts. TS Reviewer: Stephen Schneider HAVE FUN REDRAFTING EVERYONE--AND NICE WORK TO THIS POINT!! ------ Stephen H. Schneider Dept. of Biological Sciences Stanford University Stanford, CA 94305-5020 U.S.A. Tel: (650)725-9978 Fax: (650)725-4387 shs@leland.stanford.edu