**CCSP Collated Comments Prospectus 1.2**

**[NOAA Comments]{.underline}**

[General Overall Comment]{.underline}

Given, the natural link among the meridional overturning circulation
change, the Greenland ice sheet variability and the increase of
greenhouse gas is addressed in these two separate products (S&A Products
1.2 and 3.4 \[1.3i, iii, iv\]), the author teams need to coordinate
closely.

The Agency Leads for these two S&A products recognize this overlap and
plan to assist the writing teams in coordination of the two products. It
is likely that there will be cross representation on the two teams in
order to ensure coherence without redundancy, and to ensure that both
teams benefit from the work of each other.

[General Comments]{.underline}

Since the title of this SAP is ***Past Climate Variability and Change in
the Arctic and at High Latitudes***, it would be helpful if the authors
defined "Arctic" and "High Latitudes".

Discussion among the attendees at the scoping meeting led to the
decision to defer a definition of precisely how far south to extend the
definition of 'high latitudes' until the writing teams began their work.
This decision arose from the recognition that defining a hard boundary
as to which records would or would not be considered based on latitude
could potentially place undue restriction on records derived from
specific sub-polar regions the inclusion of which will provide unique
records. While 'Arctic' is generally accepted as meaning above 66° 33'N
latitude, we wish to defer articulating a definition of 'high latitude'
pending decisions on which records will be included in the synthesis and
assessment product.

The document is a little "thin" on details. For example: Which paleo
proxies provide the best opportunity for good records? Which physical
(or other) variables will the paleo record allow the authors to
investigate? What tools will they use to understand the cause and effect
they intend to elucidate? How complete (or incomplete) is the paleo
record as far as yielding information over the various regions that make
up the Arctic, i.e., regional differentiation? Admittedly, some of this
will come out of the assessment itself, but it would be nice to know
upfront what the prospects for success are and where the emphases will
be.

Paleo data are not only proxy records. Ice cores provide many direct
measurements including atmospheric gas composition and gas isotopes,
accumulation, aerosol and dust content of the atmosphere (including
isotopic concentrations in dusts), sea salt loading, and records of
unique events such as volcanic eruptions. Proxy records from ice cores
include atmospheric temperature via stable isotopes, terrestrial
productivity via entrapped pollen, and oceanic productivity from methane
sulfonate. Additional records will include but not be limited to those
derived from tree rings, pollen records, lake sediments, marine
sediments, past permafrost records, surface exposure dating, and
periglacial and other geomorphic features. Taken together, these records
will provide a comprehensive picture of past climate regimes in the
Arctic.

This is a study of the paleo record but one of the questions is**: What
will be the fate the Arctic sea ice cover in the 21^st^ century?** This
implies that projections/predictions will be referred to, but there is
no mention of this. It appears that events (e.g., warming episodes) in
the paleo record will be the sole source of inferring changes in the
future. Is this correct?

The paleo record integrates into the record of modern observation. To
the extent that the paleo record of arctic sea ice cover can provide
insight into future behaviors and/or provide some boundaries on these
behaviors, this information will be elaborated in the SAP.

A similar comment applies to the question: **How much warmer/colder,
wetter/drier is it going to get in the next 100 years?** Here the method
will presumably be "Past warm periods provide analogs for future
change". If this is true, is there sufficient information in the paleo
record?

Yes, there is sufficient information in the paleo record to provide
insights and analogy for future change provided that the record
considered extends far back enough to include prior warm periods that
are analogous to the present.

In regard to the question **What is the status of the Greenland Ice
Sheet?**, how does this relate to the Product 3.4 focus on this same
phenomenon? Product 3.4 does mention that there is some overlap. There
will have to be some coordination of approaches and/or results reported
between these two assessments.

Please see remarks under 'General Overall Comments' above. We recognize
the need to coordinate these two products.

The question **What will be the rates of change?** will, presumably, be
addressed, also, by referring solely to the paleo record, but it is not
made clear that the conditions (i.e., the forcings) that the Arctic will
experience in the future have their counterpart in the paleo record.

This point is well taken. We fully appreciate that, although the paleo
record clearly indicates that current temperatures in the Arctic are not
unprecedented, the current rates of temperature change are unusually
rapid. We anticipate that although the current rates of some changes are
more rapid than has been seen in the past, the basic mechanisms that
underlie these changes are fundamentally the same mechanisms as those
which have operated in the past.

Recommend that the author list be expanded to cover more expertise.

The list of authors given in the prospectus represents only the lead
authors for each of the questions. Lead authors will assemble writing
teams with broad expertise to develop a record that draws on as many
pertinent fields as possible. A need that was immediately recognized is
the requirement for input from the field of paleobotany in order to
incorporate information on the type and extent of prehistoric ecological
systems. We anticipate that the final product will include a much
broader information base than that represented by the makeup of the
current team of lead authors.

[Detailed Comments]{.underline}

**Page 2, line 39-40**: *"... changes in sea ice will influence weather
systems both in the Arctic and in the middle latitudes."*

Not only the weather systems but also the short term climate variability
(from submonthly to interannual timescales, including ENSO, NAO, MJO,
monsoons, etc.) are affected through complex interactions between the
lower boundary forcing and internal dynamics. The potential impact of
Arctic sea ice and Greenland ice sheet variability and change on the
predictability of weather-climate system in the middle and subtropical
latitudes, particularly over North America, could be large and should be
on the synthesis and assessment list to support national weather-climate
forecast improvement. Because of the vital importance and critical
needs, an independent question arises:

> "What is the potential impact of Arctic sea ice and Greenland ice
> sheet variability and change on the predictability of short-term
> climate and weather systems in middle and subtropical latitudes?"

This question could be the first paragraph of the first key issue in
section 1.3 (line 36-42).

The text will be modified to refer to the impact of ice variability on
the predictability of short-term climate and weather systems as
indicated in this remark, but an attempt to elaborate on the impact that
such variability may have had in the past is beyond the scope of
resolution possible this S&A.

**Page 3, lines 29-30:** I would delete \"continued retreat will
potentially impact ecotourism as well.\" Why?

**Page 5, line 7:** Use the word "Stakeholders." concur

**Page 6, line 6:** Use Kathleen, instead of Kathy. concur

**Page 6, line 21:** Insert Dr. David Verado. concur

**Page 11, line 3:** Leningrad, instead of Lenigrad. concur

**[DOE Comments]{.underline}**

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.

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 but will
entrain much older portions of the record where doing so yields
additional insights.

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

The authors declined to specify this because the spatial variability in
the Arctic is high enough to make the use of an average number
inappropriate in the prospectus.

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

The authors intend to utilize the record of past climate changes in the
Arctic to both inform the current process of change and to provide a
long-term context for it.

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'.

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.

The timetable will be amended to reflect FACA process time requirements,
but the Agency Lead will seek to expedite the process.

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.

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 21^st^ century?'  This question
can only be answered using climate change projections.

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.

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.

From these remarks we understand that by casting our key questions to
address the future we have raised a question as to what role global
climate models will play in this S&A. Since it is not the intent of the
Lead Authors to entrain the results of such models to any great extent
in S&A 1.2 we have rephrased the key questions as suggested by this
reviewer.

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.

Abrupt Climate Change in the Arctic is the sole focus of S&A Product
3.4. The focus of S&A Product 1.2 is the entire span of climate
behaviors as documented in the paleoclimate record for the high
latitudes. There is no intention to concentrate specifically or solely
on rapid events alone. We recognize the need to coordinate activities
between the two products in sections that make reference to the same
events. Please see our remarks under 'General Overall Comments'.