**Response to Public Comments on the Prospectus for SAP 1.2**

**General Comments:**

First General Comment: I was rather surprised at the summary of the
science included in the prospectus, in that I would have thought a
number of the statements (especially those sentences including the word
"will") would end up being in the results of the study rather than in
the opening statement of the situation (see specific comments for some
examples). Responses given under specific comments. We have revised the
language to be more consistent as per this suggestion.

*[\[Michael MacCracken\]]{.underline}*

Second General Comment: In preparing the CCSP synthesis and assessment
report itself, It would be helpful to very carefully explain the use of
words regarding likelihood and level of confidence. This is being done
in the IPCC report s and was done in the US National Assessment report
using lexicons that were carefully explained and other words (like "may"
and "could" were intentionally avoided as not communicating useful
information about likelihood or confidence in the statements. I would
urge that a similar sort of approach be used here.

We concur and will adopt the approach of the IPCC in this matter. This
is now noted in section 1.7.

I wish to comment on the choice of Lead Authors of SAP1.2.

I have some concern about lead author Dr J, Brigham-Grette, the lead
signer of a recent article in Eos. The signers do not distinguish
between a warming of the climate and one that is anthropogenic. Further,
to support their arguments, they misquote the findings of SAP-1.1. (see
attached). I would feel more comfortable if Gerald North and/or Kurt
Cuffey were added as lead authors.

*[\[Fred Singer\]]{.underline}*

A cadre of contributing authors and reviewers will be involved in the
production of this report. Of the two suggestions offered, Prof. Cuffey
has the appropriate expertise in paleoclimate to be engaged in this SAP.
He is currently on sabbatical and has declined to participate at the
lead author level. Dr. North's expertise lies outside the realm of
paleoclimate analysis but his climatology expertise would be most
welcome and will be sought as a reviewer.

It would be useful to know what time scales 1.2 will span. The draft
prospectus says beyond the historical period, but it's not clear how far
back in time they will go.

*[\[Jerry Elwood\]]{.underline}*

Similar to the line of reasoning arrived at during the scoping session
on drawing hard limits on the geographical definition of 'high
latitudes', the participants agreed that at the outset they would focus
on a timescale for which meaningfully-resolved records exist, for which
the role of orbital forcing would come into play, and for which good
analogs for present conditions exist. There was general consensus that
the timescale needs to be flexible enough to yield meaningful insights
and not be artificially constrained by setting a limit which might
exclude consideration of important analogs that lie outside such a
limit. Having said this, it is likely that the record to be considered
will extend back at least as far as the last full interglacial (125Kyr)
but will entrain much older portions of the record where doing so yields
additional insights.

There is a lack of reference to global coupled climate models. If the
questions raised in 1.2 dealt with determining the range of variability
based on the paleo record to provide a context of current changes in
Arctic, based on past observational and proxy data, it's fine to bypass
dealing with climate projection results. But Question 1, Question 3,
Question 4 need GCMs to answer. Question 1, Question 3, Question 4 are
all to do with future... simply analyzing the past record won't do.
There is no mention of how these will be addressed using climate change
projections.

*[\[Jerry Elwood\]]{.underline}*

Introductory material has been added to elucidate the intended
relationship between the record of the past and its implications for the
future. The questions have been rephrased to indicate this. Each of the
following questions (below) that raises the issue of the role of climate
models should be addressed by the added material. The utility of the
paleoclimate record, as intended by the authors, is to shed light on the
range of possibilities as supported by clear demonstration of prior
existence. Insofar as the past record can shed light on possible other
states it has application to potential futures. It is not the intention
of the authors to enter into the realm of global coupled climate
modeling extensively, but rather to answer the questions..'has this
happened before' and 'under what circumstances'.

**The paragraphs under Question 1**, do not deal with answering Question
1 per se. They deal with the impact of decreased sea ice cover. Either
the question should be substituted to be the one that will be answered
by the text, or the text should be altered to answer Question 1 'What
will be the fate of the Arctic sea ice in the 21st century?' This
question can only be answered using climate change projections.

*[\[Jerry Elwood\]]{.underline}*

Question 1 was rephrased in response to the earlier CCSP review and the
header text has been altered to indicate that the material presented
under each question is meant to provide both background information that
gives the reader a sense of why the question has been deemed important
(i.e. the 'so what?') and also states the relevance of the paleoclimate
record in helping to answer the question. Similarly, questions 3 and 4
have also been rephrased.

**Similarly the paragraphs under Question 3**, do not deal with
answering Question 3 per se. They deal with the impact warming would
have, and historical records. Either the question should be substituted
to be the one that will be answered by the text, or the text should be
altered to answer Question 3 'How much warmer/colder, wetter/drier is it
going to get in the next 100 years?' This question can only be answered
using climate change projections.

*[\[Jerry Elwood\]]{.underline}*

See response to prior question.

**Question 4** 'What will be the rates of change?' We'd need to refer to
climate model results. But page 4, line 44 is how the report will answer
this question, viz the report will summarize paleoclimatic data ...
filling those gaps'. I believe this will not provide the answer to
Question 4. Either change question, or change text to answer question.

*[\[Jerry Elwood\]]{.underline}*

See response to prior question.

How is 1.2 related to 3.4? 1.2 will look at Abrupt Climate Change in the
Arctic; 3.4 deals solely with Abrupt Climate Change. So will both deal
with Abrupt Climate Change. It is not clear where climate processes will
be dealt, under 1.2 or 3.4? Given these assessment products in the same
stage of evolution, there needs to be some cross-talk so redundancy is
reduced.

*[\[Jerry Elwood\]]{.underline}*

This is now specifically addressed on pg.6 line 28. The paleoclimate
record is the only extant record of abrupt climate change. The timing,
scope, and extent of the past abrupt events will be examined in SAP 1.2,
with discussions of causes and impacts where the record supports them
(e.g. the paleoclimate evidence for the outburst flooding from Lake
Agassiz and the subsequent cooling and freshening of North Atlantic
surface water 8.2Kybp). The discussion of the climate processes for
these event will be dealt with in depth in SAP 3.4. The overlap of the
two products is recognized and a plan for cross-communication between
the two writing teams is in place.

**Specific Comments:**

**Page 1 Line 43**: can you put numbers on 30 year trend in Arctic?

(comment not addressed, why not?)

We feel that we did address this question in our response. To
reiterate... any numbers that state specific [average]{.underline}
temperature changes in the prospectus have the potential to be
misleading in the face of the large spatial variability of average
temperatures in the Arctic over the past 30 years. The authors do not
wish to create a level of specificity where it is likely to be
misinterpreted in the prospectus. A general statement about air
temperatures over Arctic land masses in the 20^th^ century has been
added

**Page 2 Line 44**: Some of these are already occurring. Why is the
draft prospectus talking in future tense.

(comment addressed, OK)

*[\[Jerry Elwood\]]{.underline}*

Text has been adjusted..

**Page 3 Lines 9-15**: How will the CCSP product address this, if at
all? What is the relevance of this para to 1.2? Page 3, line 32 also
refers to iceberg distribution and 'thus shipping'.

Section deleted.

*[\[Jerry Elwood\]]{.underline}*

**Page 8**: Final prospectus is scheduled for Dec 2006. It will take at
least a couple of months before FACA committee is approved. Page 9
timetable is not realistic.

FACA approval has been received. The timeline has been adjusted to
reflect this.

**Page 1, line 43**: An uncertainty range should be associated with the
amount of overall warming.

*[\[Michael MacCracken\]]{.underline}*

Uncertainty range has been inserted.

**Page 1, line 45**: The phrase "although the variability is also
greater in the Arctic" seems a bit strange. First, it should explicitly
say greater than what, but more importantly, it is not made clear why
this is important and what the time scale of the variability being
talked about is? Is it the century long variability, or over the 30
years or what? And is the comparison to the variability over a small
region like the Arctic to the planet as a whole, to other latitude
bands, or to other regions of similar size around the world---it is just
not clear what is meant. And, a key issue for the Arctic is having
representative data across the whole region over the times of the
comparison---there is little observational data over much of the Arctic
for period prior to 1950, so some of the variability likely being
referred to (i.e., that during the early 20^th^ century) is compromised
by the changing coverage of data. Finally, on this point, in that
human-induced climate change for the Northern Hemisphere, as
reconstructed by the models, extends back through the 20^th^ century and
has a similar pattern to the observed trends in the North Atlantic (and
sulfate aerosols likely played a role in the temporal pattern, it is not
really clear what was variability and what was change. I would hope that
this assessment report would address a number of these questions, so
seeing them apparently settled in the prospectus seems a bit troubling.

*[\[Michael MacCracken\]]{.underline}*

The phrase has been deleted. The authors appreciate the suggestion to
ensure that the variability/change issue is adequately addressed in the
report.

**Page 2, lines 3-4**: The shallow inversion in the Arctic also plays a
role in making it a more sensitive region---less mass of air to be
affected.

*[\[Michael MacCracken\]]{.underline}*

Noted

**Page 2, lines 9-11**: Just to note that the Arctic Climate Impact
Assessment also found it useful, at least for the early 20^th^ century
and in regions where formal observations were lacking, to draw forth
information about climate and climate proxies from the recollections of
elders. Proxy information such as the appearance or absence of certain
species (like birds, insects, etc.) can give a useful sense about
whether conditions during the early-mid 20^th^ century were comparable
to those today. So, I would urge consideration be given to traditional
knowledge as a useful augmentation of traditional proxy indicators,
seeking, of course, to also find collaborating evidence of other types.

*[\[Michael MacCracken\]]{.underline}*

Indigenous knowledge will be very valuable in filling the gaps between
the paleo-record and the instrumental record and in elucidating impacts
to human and animal populations. The authors will seek a contributing
author to cover this aspect of the record.

**Page 2, lines 25-27**: The words used here need to be clarified, in
particular, what does "in the recent geologic past" mean? My
understanding is that, from studies of the presence of trees and boreal
habitat, that the Arctic has not been warmer than at present since the
Holocene Optimum some 6000 years ago when Milankovitch forcing was quite
different---is 6000 years ago the "recent geologic past," or does this
term mean earlier or later. In that this phrasing could be misconstrued
to mean that the present warming is not all that unusual, this phrasing
needs to be made much more specific.

In the context of the prospectus text the 'recent geologic past' is
taken to mean the past 125K years. However this phrase is likely to
suggest some unintended constraints on the use of paleo-data. It has
therefore been deleted.

*[\[Michael MacCracken\]]{.underline}*

**Page 2, line 42 to Page 3, line 2**: This paragraph is one where
careful application of the lexicon would seem to be needed. First, the
paragraph indicates that "reduction in sea ice *will* accelerate" and
then that this "*will* influence weather systems" (so, in both cases
suggesting complete certainty, but all in qualitative terms, so this
does seem reasonable) and then it is said, "changes in ice cover and
freshwater flux out of the Arctic Ocean *may* also affect ..."
\[emphasis added\]. I would suggest that if one says "will" in the first
two cases, then "will" should apply in the same sense for the third
phrase---these are qualitative and not quantitative sentences and doing
otherwise implies some sort of judgment is being made about quantitative
aspects and importance. If that is the case, then all the phrases should
be couched in a lexicon like that of the IPCC (i.e., virtually certain,
very likely, etc.). This problem continues in the next paragraph, where
it is said that "reduction of sea ice will also accelerate coastal
erosion" and "food web will change" but only that wildlife "are likely
to be adversely affected." Then the assertion is made that "a loss of
sea ice will allow for greater commercial exploitation" without seeming
to consider a number of qualifications that are likely applicable, such
as whether this can be done with permafrost melting, the potential of
hazards and pollution and clean-up liabilities and capacity, issues of
sovereignty, problems and liabilities associated with shipping in
dangerous waters for ice-free seasons of varying length and intensity,
etc.---and so on.

*[\[Michael MacCracken\]]{.underline}*

Text has been rewritten to be more self-consistent. The examples given
in these sections are meant to provide background for why the question
being asked in the SAP has relevance to human and animal populations.
The statement that a 'reduction of sea ice will allow for greater
commercial exploitation...' has been amended to read ''The loss of sea
ice will also provide the opportunity for greater commercial
exploitation....'. However, both statements simply make the point that,
all other things being equal, an open sea route will provide additional
access for activities which are currently limited by the presence of sea
ice.

**Page 2, line 10**: Just to note that in the Arctic Climate Impact
Assessment, the term "northern sea route" was used as this is apparently
preferable to "northeast passage."

*[\[Michael MacCracken\]]{.underline}*

Text changed to this wording.

**Page 2, lines 23-25**: More uses of the word "will"---the first is
fine, but it should not be implied that this report will provide a full
context for evaluating current and future impacts---this will take much
more than paleoclimatic information.

*[\[Michael MacCracken\]]{.underline}*

This has been a difficult line to walk. The authors do not intend that
this report will provide a full context for evaluating current and
future impacts. As Michael observes, that is well beyond the scope of
the paleoclimate record alone. But they do intend that the relevance of
the paleo-record to the present and future is made clear in a
supportable way.

**Page 2, lines 33 and 39**: Why is the word "could" now being used---in
the framing earlier of qualitative statements, "will " is as
valid---"could" is really an innocuous and ill-defined word and should
be replaced by a word in whatever lexicon is to be drawn upon. Similar
issues arise throughout later paragraphs, and not being careful in the
prospectus would seem to bode ill for the report itself.

*[\[Michael MacCracken\]]{.underline}*

In the two particular instances in which 'could' was used, - the first
referring to the breakdown of clathrates in the Arctic shelf and the
second referring to undersea landslides generated by destabilization of
the continental shelf -- the proposed mechanisms are plausible, but have
yet to be demonstrated to have happened through a clear chain of
evidence in the paleo-record. We therefore feel that the use of 'could'
rather than 'will' is more appropriate in these instances.

**Page 2, line 46**: Switch "is it" to "it is"

*[\[Michael MacCracken\]]{.underline}*

Corrected

**Page 3, lines 37-38**: The phrase "are superimposed" seems a poor
choice of words, for it seems to somehow imply that we'll continue to
have conditions like the present, with the baseline just a bit higher.
Actually, the change in the baseline is going to overwhelm natural
variability. Indeed, there will be some variations remaining, but not
like the present ones.

*[\[Michael MacCracken\]]{.underline}*

Text amended to reflect this.

**Page 3, lines 40-42**: It is not at all clear that future variability
will be like past variability, and the "changes of even larger
magnitude" that have occurred in the past were, as I understand it, when
the surrounding continental areas were generally ice-covered and massive
melting and formation of glacial lakes led to outflows that dramatically
affected ocean circulations. Such circumstances don't exist now, and to
imply that one could get such large variations now seems quite
misleading, unless there is a real though that accelerated melting of
Greenland could lead to this, and if that is to be the cause, then the
text should indicate this and what it would be meaning for changes in
sea level. As the text is now, it seems to me to underplay the important
changes human activities are inducing.

*[\[Michael MacCracken\]]{.underline}*

Text has been added (pg. 5, 22-25) that explicitly recognizes that past
warm periods are not necessarily completely analogous to the current
warm period. Nevertheless, the fact remains that we do not yet fully
understand where the triggers for abrupt climate change lie and that our
best clues to this lie in the record of past changes.

**Page 8, lines 15-22**: That this prospectus on line 22 indicates that
the lead authors will participate in the final responses to comments
from the NSTC level review is encouraging for it seems to go beyond the
published guidelines (see the Web site of the guidelines). Thus, this
paragraph, indicating conformance between this prospectus and the
guidelines seems not to be fully the case, and it is about time the
guidelines were revised, as not having the lead authors involved in the
finalization of the document would make it into a political document and
greatly diminish its credibility.

*[\[Michael MacCracken\]]{.underline}*

It is the understanding of the authors that they will be engaged in all
phases of the review process and that once the final language is agreed
upon between the NSTC reviewers and the authors, no re-writing can
occur.