Thursday, June 14, 2012


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
TS Reviewer: Stephen Schneider

pg 11; lns28-30: Is this language confusing the WG1 "likehood" with the
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
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
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
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
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
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
TS Reviewer: Stephen Schneider


Stephen H. Schneider
Dept. of Biological Sciences
Stanford University
Stanford, CA 94305-5020 U.S.A.

Tel: (650)725-9978
Fax: (650)725-4387

No comments:

Post a Comment