CCSP SAP3.1 Climate Models: An Assessment of Strengths and Limitations : CCSP SAP3.1 Climate Models: An Assessment of Strengths and Limitations Status and Plans
8 August 2007
SAP3.1 Recent History & Schedule* : SAP3.1 Recent History & Schedule* 07 February 2007: First Draft to peer reviewers
22 May 2007: Second (Public Review) Draft released together with response to peer reviews
06 July 2007: Deadline for public review comments
25 July 2007: Extensive additional comments from CPDAC member Dick Lindzen
E-mail discussion initiated between Lead Authors and Lindzen
Isaac Held volunteers to lead rewrite of climate sensitivity section
31 July 2007: “First draft” response to public comments from Bader and Covey to other SAP3.1 Lead Authors
Most but not all LAs replied to first-draft response as of 02 August: so far, consensus on how to respond to public comments
Sep 2007: Third Draft to be released?
Oct 2007: Final report to be published? **
* according to www.climatescience.gov/Library/sap/sap3-1
(31 Jul 2007)
** final technical editing, copy editing and production by ORNL
Response to Peer Reviews : Response to Peer Reviews Response = 40-page PDF document including original comments.
Reviewer #4 (Mote) comments received late (18 Apr 2007). Responded only to general comments, which were similar to those of other reviewers.
Virtually all comments were constructive and were used to help write the Second (Public Review) Draft.
Major Peer Review Comments : Major Peer Review Comments “The tone of the piece is uneven.” (repeated)
Response: Text rewritten throughout subsequent draft to balance length of discussion of different topics and simplify technical points.
Sections on coupled GCM creation and reductive vs. holistic evaluation of models seem “out of place” and “sit uneasily in this report” but “convey something useful about how GCMers work and think.” Disturbing implication “that modeling groups essentially cheat by tuning equilibrium climate sensitivity.”
Response: Misleading language removed and sections combined / condensed in subsequent draft.
Focusing on just 3 US modeling groups “does not give an accurate overview of the ability of GCMs in general . . . too restrictive.” (repeated)
Response: Subsequent draft adds summaries of full IPCC AR4 (CMIP3) model results. The 3 US groups provide examples of GCMs in general (e.g. in ENSO section). Emphasis on US models is appropriate for US target audience.
“Unfortunately, much of the draft does not address user applications and appears to be directed at climate scientists, not decision makers.”
[see response to first comment]
Public Reviews of Second Draft : Public Reviews of Second Draft Received from only four sources:
NOAA Research Council
California Department of Water Resources
NOAA Office of Federal Coordinator for Meteorology
NSF
Many detailed comments down to the level of spelling and punctuation (useful proofreading)
Appropriate response to comments seems possible with only minor changes to text
Lindzen’s Comments on SAP3.1 : Lindzen’s Comments on SAP3.1 Very extensive; received just 2 weeks ago.
Criticize undue emphasis on “consensus among models”
Multi-model ensemble averages questionable: “right answer for wrong reasons”?
Criticize model-inferred climate sensitivity
Model / observation discrepancy in relative warming of surface and troposphere (SAP1.1 Fig. 5.4G) < 1/2 of recent global warming is anthropogenic (Lindzen’s new unpublished manuscript)
PDO obs response time of climate system, which scales with climate sensitivity real-world climate sensitivity < models (Roe’s new unpublished manuscript)
Strategy for Responding to Lindzen’s Comments : Strategy for Responding to Lindzen’s Comments Take enough time to respond seriously . . .
Third draft may slip past September 2007.
. . . but don’t wander off SAP3.1’s designated topic.
“The intended use of this CCSP product is to provide information to those who use climate models about the strengths and limitations associated with using models to project the potential effects of human activities on climate and sea-level rise.” (-- Prospectus)
Make direct comparisons between observations and models.
Note that Lindzen’s upper bound to anthropogenic climate change connects to radiosonde-measured tropospheric warming, which on its face disagrees with models.
Note error bars in both observations and models.
For observations of tropospheric warming, SAP1.1 and subsequent published papers point out errors.
Spread of model results is a lower limit on uncertainty of theory.