[CCSM-participants] Draft plan for CMIP5 (IPCC AR5 model output)

[Barbara Ballard]

Dear all,

As most of you know, plans are well underway for a coordinated set of 
climate model experiments, which will constitute the Fifth phase of 
CMIP.  Attached is a description of the proposed experiments.   As 
members of the CMIP panel, which was established by the WCRP's Working 
Group on Coupled Modelling (WGCM) to help coordinate this activity, we 
are seeking your comments.  Considerable thought and input from a wide 
community of scientists have already contributed to the CMIP5 design, 
and therefore major changes are not envisioned.  Competing interests and 
various tradeoffs have been carefully considered before coming up with 
the proposed suite of experiments.  Please keep in mind that modeling 
groups have limited resources and the experiment must represent a 
compromise among various priorities. We will not be able to please everyone.

The CMIP panel must present a final design plan for CMIP5 to the WGCM at 
its annual meeting in September, just two months from now.   Given this 
tight deadline (which cannot slip if the CMIP5 results are to be 
available in time for the IPCC's Fifth Assessment Report).   For this 
reason, we ask that you send us (taylor13 at llnl.gov and  
Ronald.Stouffer at noaa.gov) any comments and suggestions you have by 
September 1, 2008.
Feel free to pass this document on to anyone you think will have an 
interest in it.  We invite comments from scientists associated with all 
aspects of the climate change issue, spanning the three IPCC working groups.

With best regards,
Karl Taylor (PCMDI) and Ron Stouffer (Chair, CMIP panel).

P.S. Please note that there are remaining details yet to be worked out.  
In particular it has been suggested that experiments 4.2 a&b described 
in the document should be performed in conjunction with the so-called 
RCP-driven experiments given in Table 2 rather than with the idealized 
(1% CO2 increase per year) experiments of Table 4.  Experiments 4.2 
allow us to separate out the climate-carbon cycle feedback. The original 
proposal was in fact to do this separation for the RCP runs, but several 
scientists offered compelling arguments for switching this diagnostic 
analysis to the 1% runs.  Some of the reasons for making this change 
from the original proposal can be found in section 9.  Still, there are 
some scientists who continue to express a preference for the original 
design.  Please let us know what you think about this.

-- 
Barbara Ballard
Administrative Assistant III
CCSM Program Office
Oceanography Section
National Center for Atmospheric Research
P.O. Box 3000
Boulder, CO  80307-3000
Phone: (303) 497-1358
Fax:   (303) 497-1700