**Draft Prospectus 3.4 "*Abrupt Climate Change*"**

Collated Public Comments

7 November 2007 -- 7 December 2007

**Reviewers**

**1- Meric Srokosz, Ph.D.**

National Oceanography Centre,

Southampton (NOCS), Empress Dock, Southampton, SO14 3ZH, UK

Tel:+44-(0)23-80596414 (direct line); Fax: +44-(0)23-80596400

e-mail: mas@noc.soton.ac.uk or M.Srokosz@noc.soton.ac.uk

http://www.noc.soton.ac.uk/JRD/SAT/pers/mas.html

Science Coordinator NERC Rapid Climate Change Programme

http://rapid.nerc.ac.uk/

**2- James F. Todd, Ph.D.**

Program Manager, Climate Variability and Predictability Program

NOAA Office of Global Programs

1100 Wayne Avenue, Suite 1210 Silver Spring, Maryland 20910-5603 USA

Phone: 301-427-2383 (after 11/20/2006, 301-734-1258)

FAX: E-mail: james.todd@noaa.gov

**3- Brigid DeCoursey or Camille Mittelholtz**

Office of Safety, Energy, and Environment

Office of the Secretary-U.S. Department of Transportation

400 7th St., SW Washington, DC 20590

Phone: (202) 366-8914

Fax: (202) 366-7618

**4- Ashley D. Williamson**

\(301\) 903-3120

ashley.williamson@science.doe.gov

On Behalf of Jerry Elwood

\(301\) 903-3281

Jerry.Elwood@science.doe.gov

**5- Michael MacCracken, Ph.D.**

Climate Institute

1785 Massachusetts Ave., NW, Suite 100, Washington DC 20036

Phone: 301-564-4255

E-mail: mmaccrac@comcast.net

Areas of expertise: Climate change, climate impacts, and assessment

**6- Jochem Marotzke, Ph.D.**

Max Planck Institute for Meteorology

Bundesstr. 53 D-20146 Hamburg GERMANY

Tel.: +49 (0)40 41173 - 440

Tel.: +49 (0)40 41173 - 311, -467 (secretary)

Fax: +49 (0)40 41173 - 366

jochem.marotzke@zmaw.de http://www.mpimet.mpg.de/

Areas of expertise: Ocean and climate dynamics, Abrupt climate change,
Atlantic thermohaline circulation

**General Comments:**

Your lead authors (section 3) do not have anyone representative of the
oceanographic observing community working on the MOC - in the USA you
could co-opt Prof. Bill Johns of RSMAS, Miami University, who is heavily
involved in observing the N. Atlantic MOC.

*[\[Meric Srokosz\]]{.underline}*

\-\--This issue will be addressed by inviting at least one member of the
oceanographic observing community to attend/speak at the SAP workshops
and participate in the writing process as contributing author.

In the section regarding the meridional overturning circulation (MOC),
the report authors should be aware of the science coming out of the UK
RAPID program, in which the US is a participant. There have been several
recent advances in our understanding of MOC variability from this
effort. Further, the UK RAPID effort seems to be much more up-to-date
with respect to the attack on the problem - when contrasted with this
report. For instance, it seems that it would be very important to ask
the question \"What is the present state of the MOC?\"

I would suggest that the following individuals be considered part of the
writing team:

Jeff Severinghaus (Scripps)

David Battisti (Univ. Washington)

Bill Johns (RSMAS)

Peter Schlosser (LDEO)

Ray Pierrehumbert (Univ. Chicago)

*[\[James F. Todd\]]{.underline}*

\-\--We added the following as a primary question to be addressed in the
SAP prospectus: "What is the present state of the MOC?" The
oceanographic observing community will be involved in both the workshops
and the writing process (see response to comment above). We will
consider the individuals mentioned in this comment.

SAP 3.4 seems to reflect some of the information that was in the NASA
presentation on the polar ice caps given at the September \"blue-box\"
meeting. This prospectus does not seem to reflect any coordination with
this work. We suggest coordination with NASA.

*[\[Brigid DeCoursey or Camille Mittelholtz\]]{.underline}*

\-\--The coordination team for SAP 3.4 will investigate the ways in
which NASA may become involved in this process. We will make sure that
there is representation at the workshops and on the writing team.

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}*

\-\-- The members of the Organizing Committees for SAP 1.2 (*Past
Climate Variability and Change in the Arctic and at High Latitudes)* and
3.4 (*Abrupt Climate Change*) have met to address the issue raised in
several reviewers' comments regarding the potential for overlap between
these two products. The members have agreed on the following process in
order to ensure that a large-scale duplication of effort does not occur
and that the two synthesis and assessment products achieve maximum
impact.

Based on the individual scopes identified in the respective prospectuses
of the two products, the Organizing Committees will issue guidance to
the writing teams regarding the potential for overlap and suggest a
logical separation of emphasis. Examples of these areas of emphasis are
given below.

Communication between the two writing teams will be established through
joint representation from the respective SAP's organizing committees at
each others' workshops.

As the outlines for the individual products are developed, the
coordinating lead authors for both SAPs will be asked to review each
others' outlines to identify and resolve potential redundancies before
major sections of the reports are written.

Areas of Emphasis -- Examples

  ---------------------------------- ------------------------------------
  SAP 1.2                            SAP 3.4

                                     

  Evidence for past abrupt changes   Evidence for past abrupt changes in
  in the Arctic paleoclimate record. the global record.

  Extent of impacts as evidenced in  Factors controlling abrupt change
  Arctic paleo-records.              events and evaluation of global
                                     impacts

  No emphasis                        Evaluation of models in simulating
                                     or predicting abrupt change events

  Steady-state inputs into the       No emphasis
  paleoclimate record                

  Evidence for rapid ice melt in     Mechanisms for rapid ice melt
  past arctic records                
  ---------------------------------- ------------------------------------

First General Comment: This prospectus describes an interesting,
excellent and very important effort. It should certainly go forward and
be well supported.

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

\-\--No action necessary.

Second General Comment: In the discussion of Question iv that the report
will consider, a particularly important instance of apparently rapid ice
sheet melting that should be presented and evaluated is the lead-in to
the Eemian interglacial, when there are some indications that melting of
the Greenland and/or Antarctic ice sheets could have been contributing
to a rate of sea level rise of order 1 meter/century.

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

\-\--We thank the author for this advice. The Committee will consider
the Eemian interglacial period while dealing with question #1 in Section
iv: "What is the paleoclimate evidence regarding rates of rapid ice
sheet melting?"

Third General Comment: In addressing each of the four questions, the
report should make clear the limitations of the analyses done to date
(e.g., as reported on in the IPCC assessments), and compare the
potential magnitude and rate of what is found in these studies with the
magnitudes and rates of the estimates contained in the IPCC assessments.
This would greatly help in making clear that the findings reported by
the IPCC and agreed to unanimously by roughly 150 countries over the
past two decades have necessarily not included a full characterization
of the risks posed by human-induced climate change, meaning that the
published IPCC estimates are actually conservative rather than worst
case.

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

\-\--This advice will be presented to the Committee at the first
workshop for their consideration.

One quick comment on the prospectus: It is disappointing that, although
the report aims to investigate the Atlantic MOC, among other phenomena,
there is no expertise on or even real mention of measuring its current
state. In that, the report, from its basic design, is not even up to
date with the RAPID programme, which as one of its great successes has
brought together observations of the modern ocean and climate modelling
(plus strengthening ties with palaeo). It would be important to remedy
that problem, lest the report be marred by being obsolete before it\'s
written. The easiest (?) would be to add Bill Johns (Univ. Miami) to the
list of authors.

Info on the NERC UK funded RAPID, with significant additional funding
from NOAA and NSF:

<http://www.soc.soton.ac.uk/rapid/>

*[\[Jochem Marotzke\]]{.underline}*

\-\--See responses to general comments #1 and #2 above.

**Specific Comments:**

Page 6, lines 5-6: It should be noted whether this comparison is on a
per molecule or per mass basis.

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

\-\--The author of this comment refers to this sentence from the draft
prospectus: "Methane is a powerful greenhouse gas, and is about 24 times
more effective at absorbing long wave radiation than is carbon dioxide."
The sentence was change to read: "Methane is a powerful greenhouse gas,
and is about 24 times more effective on a mass basis at absorbing long
wave radiation than is carbon dioxide."

Page 9, lines 26: I was very pleased to see that "\[a\]ll comments and
responses," presumably to all stages of the review process described in
section 6 of the Prospectus, "will be documented and made publicly
available." This will be an important step in contributing to the
credibility of the report, and this should be the case for all CCSP
products.

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

\-\--No action necessary.