PMIP Newsletter 5
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PALEOCLIMATE MODELING INTERCOMPARISON PROJECT
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Newsletter N. 5
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23 September 1994
Dear participant,
We thank you (the modeling groups) for having answered the
questionaire.
In the present newsletter, we would like to inform you about :
-A- new specifications for the COMPUTED SST CONTROL RUN experiment
-B- a summary of PMIP experiments
-C- the list of participants in PMIP as obtained from your responses
to the questionaire.
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-A- A CONTROL RUN FOR COMPUTED SST EXPERIMENTS
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John Kutzbach has noticed a problem in the PMIP experimental design
that may complicate comparisons between the model-simulated changes and
the paleo record. In the computed-SST experiment (typically run with a
"slab" or mixed layer ocean), when the CO2 is changed from the
PMIP-recommended value of 345 ppm in the "control run" to the LGM (Last
Glacial Maximum near 21 ka BP) value of 200 ppm, an unrealistically
large global cooling might result. Part of the explanation for such a
disagreement between model and data would be that the current climate
and certainly the modern pollen and plankton have not yet come into
equilbrium with the recent rapid rise in CO2 (345 ppm). "Modern" plankton in
ocean core tops are subject to bioturbation and may represent a century
or several-century average. Modern pollen data may also represent a
time average and in addition must be corrected to remove the effects of
human disturbances. John argues that it would be better to compare
the paleoreconstructions of climate change with simulated equilibrium
change in climate between 21 ka BP and recent PREINDUSTRIAL times.
At this stage we are of course very reluctant to change the original
PMIP experimental design. It appears that several groups have begun
various prescribed SST experiments, but few have actually carried out
the mixed-layer experiments (at least not both the control and last
glacial maximum simulations). We therefore propose :
- to leave unchanged the original PMIP specifications for the
prescribed SST simulations, for which the impact of CO2 changes
from 345 to 280 should be largely damped by the use of prescribed SSTs,
- but to modify the recommended specifications for computed SST experiments
in a way that will minimize any wasted effort by individual modeling
groups while making the experiment more compatible with the paleo record.
Specifically, we recommend that for the computed SST experiment, a
"preindustrial" case replace the "present-day" control. The only
change required from the previously recommended PMIP boundary
conditions is to set the CO2 concentration to 280 ppm (instead of 345
ppm). The new recommended values for CO2 concentration are as
follows:
Prescribed SST experiments:
present-day "control" [CO2]=345 ppm
6 ka BP [CO2]=280 ppm
21 ka BP [CO2]=200 ppm
Computed SST experiments:
preindustrial "control" [CO2]=280 ppm
21 ka BP [CO2]=200 ppm
Note that the only change from the original PMIP specifications is in
the CO2 concentration for the "control" run of the 21 ka computed SST
experiment. Although we are now recommending the above values for CO2
concentration, the essential requirement for PMIP is that the radiative
forcing be the same for all groups. Thus it would be permissible to
specify slightly different values for CO2 concentration AS LONG AS THE
PROPER RATIOS ARE PRESERVED:
Computed SST experiment:
preindustrial/21 ka = 280/200 = 1.400
If, for example, you have already carried out a "control" computed SST
experiment with [CO2]=345 ppm, and you want to avoid repeating the
experiment with 280 ppm, you may instead elect to carry out your 21 ka
simulation with [CO2]=345/1.4=246 ppm. This should give you the same
radiative forcing as you would have obtained using 280 ppm and 200 ppm
for the "control" and 21 ka simulations, respectively.
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-B- SUMMARY OF PMIP RUNS
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WITH PRESCRIBED SST WITH COMPUTED SST
______________________________________________________________________
I PRESENT-DAY I PRE-INDUSTRIAL
I ----------- I --------------
control I present SST I -
I present insolation I present insolation
I CO2= 345 ppm I CO2 = 280 ppm
______________________________________________________________________
I I
6 kyr BP I SST = NO CHANGE I NOT A PMIP RUN
I Insolation 6 kyr BP I
I CO2 = 280 ppm I
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I I
21 kyr BP I Change in SST (CLIMAP, 81) I -
I Ice sheets Peltier I Ice sheets Peltier
I CO2 = 200 ppm I CO2 = 200 ppm
I Insolation 21 kyr BP I Insolation 21 kyr BP
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For 6 kyr BP, more information can be found in the PMIP newsletter 1.
For 21 kyr BP, more information can be found in the PMIP newsletters 2, 3,
and 5.
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-C- LIST OF PMIP PARTICIPANTS
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__________________________________________________________
GROUP - CODE - 6 KBP - 21KBP - 21KBP
- - Fixed - Fixed - Comp.
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COHMAP - CCM1 (R15) - YES - YES - YES
J. Kutzbach - CCM2 (T42) -
B. Gallimore - GENESIS (T42)?- Spring 1995
P. Behling et al- -
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GENESIS ESM - GENESIS 2 - YES - YES - YES
S. Thompson - T42 L18 -
D. Pollard - - Spring/summer 95
J. Bergengren - -
L. Law-Evans - -
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GENESIS/LLNL - GENESIS - YES - YES - YES
K. Taylor - R15 L12 - 6/95 - 6/95 - 1/95
L. Sloan - - - -
__________________________________________________________
GFDL - GFDL - YES - YES - YES
A. J. Broccoli - R30 L20 -
C. F. Ip - - First half of 1995
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GISS - NASA/GISS II - YES - YES - YES
R. Webb - 4x5 -
D. Rind - - Spring 1995
R. Healy - -
J. Overpeck - -
__________________________________________________________
UNIV. ILLINOIS - UI model - YES - YES - YES
M. Schlesinger - 4x5 -
M. Verbitsky - - Fall 1995
A. Ghanem - -
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CCCMA/U. Toronto- CCC - YES - ? - ?
N. McFarlane - T32L10 - done - -
R. Peltier - - - -
G. Vettoretti - -
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UKMO - HC - YES - ? - YES
C. Hewitt - 2.5x3.75,L19 - 10/94 - - 3/95
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UGAMP - UGAMP - YES - YES - YES
P. Valdes - T42 L19 - done - 12/94 - 6/95
D. Buwen - - - -
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LMCE - LMD4 - YES - YES - YES
S. Joussaume - 48x36, L11 - Fall 94 - Winter 94
N. de Noblet - - -
G. Ramstein - LMD 5bis - YES - YES - NO
P. Braconnot - 64x50, L11 - Fall/Winter 94
V. Masson - -
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U. Bremen/MPI - ECHAM - YES - YES - NO
S. Lorenz - T42L19 - done - started
M.Lautenschlager- -
P. Helbig - -
B. Grieger - -
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YONU GCM group - YONU GCM(Tr7) - YES - YES - NO
Jai-Ho Oh - 4x5, L7 - end 94 -
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MRI - MRI II - YES - YES - YES
A. Kitoh - 5x4,L15 - 9/94 - fall/winter 94
H. Koide - - -
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CCSR - CCSR/NIES - YES - YES - ?
A. Abe-Ouchi - T21 - -
A. Sumi - and/or T42 - May 1995 -
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BMRC - BMRC 3.4 - YES - YES - YES
B. McAvaney - R21 L9 - done - beg95 - started
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Antarctic CRC - MUGCM - YES - YES - YES
X. Wu - R21 or R31 - - - 1rst
W. F. Budd - L9 - Mid 1995
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CSIRO - CSIRO GCM 4.6 - YES - YES - YES
J. Syktus - 6k = R21, R42 -
- 21k= R21 - May 1995
- L9 -
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other types of models
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__________________________________________________________
LLN - 2-D LLN model - YES - YES - YES
A. Berger - - to be defined
et al. - -
__________________________________________________________
Moscow Univ. - simplified - YES - YES - NO
A. Kislov - GCM -
et al. - -
__________________________________________________________
Yours sincerely,
Sylvie Joussaume (LMCE)
Karl Taylor (PCMDI)
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Contact Address:
################
Laboratoire de Modelisation du Climat et de l´Environnement
D.S.M. / Orme des Merisiers / Bat. 709
C.E. Saclay
9119 Gif-sur-Yvette cedex
FRANCE
Tel.: (33) 1 69.08.77.11
Fax.: (33) 1 69.08.77.16
email: paleo (NEW! Please check the PMIP 'Contacts' web page)
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