**Model Information of Potential Use to the IPCC Lead Authors and the
AR4.**

**IPSL-CM4 model.**

22 Februry 2005

# Model identity:

A.  Institution, sponsoring agency, country

    -   Institution: Institut Pierre Simon Laplace (IPSL)

    -   Main sponsoring agencies: CNRS, CEA.

    -   Country: France

B.  Model name (and names of component atmospheric, ocean, sea ice, etc.
    models)

    -   coupled model: IPSL-CM4 *(TAR = IPCL-CM2)*

    -   atmosphere: LMDZ-4 *(TAR = LMD5)*

    -   land-vegetation: ORCHIDEE *(TAR = SECHIBA)*

    -   ocean: ORCA *(TAR = OPA-7)*

    -   sea-ice: LIM *(TAR = IGLOO)*

C.  Vintage (i.e., year that model version was first used in a published
    application)

    -   2005

D.  General published references and web pages

    -   Coupled model:

The IPSL climate system model: IPSL-CM4

<http://dods.ipsl.jussieu.fr/omamce/IPSLCM4/DocIPSLCM4/FILES/DocIPSLCM4.pdf>

-   Atmospheric model.

Hourdin, F., I. Musat, S. Bony, P. Braconnot, F. Codron, J.-L. Dufresne,
L. Fairhead, M.-A. Filiberti, P. Friedlingstein, J.-Y. Grandpeix, G.
Krinner, P. LeVan, Z.-X. Li, F. Lott: The LMDZ4 general circulation
model: climate performance and sensitivity to parametrized physics with
emphasis on tropical convection. Climate Dynamics, submitted, 2005.

Also see the atmospheric part of the coupled model documentation above.

-   Ocean model.

OPA reference manual (Madec at al 1998) available on the web
<http://www.lodyc.jussieu.fr/opa/Docu_Free/Doc_models/Doc_OPA8.1.pdf>

-   Sea-ice model.

Fichefet, T., and M.A. Morales Maqueda, Sensitivity of a global sea ice
model to the treatment of ice thermodynamics and dynamics, J. Geophys.
Res., 102, 12,609-12,646, 1997.

Goosse, H., and T. Fichefet, Importance of ice-ocean interactions for
the global ocean circulation: A model study, J. Geophys. Res., 104,
23,337-23,355, 1999.

-   Land-Surface model.

Krinner, G., N. Viovy, N. de Noblet-Ducoudré, J. Ogée, J. Polcher, P.
Friedlingstein, P. Ciais, S. Sitch and I. C. Prentice, A dynamic global
vegetation model for studies of the coupled atmosphere-biosphere system.
Global Biogeochemical Cycles, in press.

[ORCHIDEE documenation :
http://www.ipsl.jussieu.fr/\~ssipsl/doc/doc_main.html](http://www.ipsl.jussieu.fr/~ssipsl/doc/doc_main.html)

-   Coupler.

OASIS3 users guide:
<http://www.cerfacs.fr/globc/software/oasis/oasis3_UserGuide.pdf>

Sophie Valcke, Arnaud Caubel, Reiner Vogelsang, Damien Declat. 2004:
OASIS3 Ocean Atmosphere Sea Ice Soil User\'s Guide Technical Report
TR/CMGC/04/68, CERFACS, Toulouse, France

E.  References that document changes over the last \~5 years (i.e.,
    since the IPCC TAR) in the coupled model or its components. We are
    specifically looking for references that document changes in some
    aspect(s) of model performance.

F.  IPCC model version\'s global climate sensitivity (KW^-1^m^2^) to
    increase in CO~2~ and how it was determined (slab ocean expt.,
    transient expt\--Gregory method, ±2K Cess expt., etc.)

slab ocean: T = 4.4K; F = 3.48W.m^-2^;  = 1.26 KW^-1^m^2^

G.  Contacts (name and email addresses), as appropriate, for:

    1.  coupled model

Jean-Louis Dufresne \<Jean-Louis.Dufresne@lmd.jussieu.fr\>

Pascale Braconnot \<pasb@lsce.saclay.cea.fr\>

2.  atmosphere

Frederic Hourdin \<Frederic.Hourdin@lmd.jussieu.fr\>

3.  ocean

Gurvan Madec \<Gurvan.Madec@lodyc.jussieu.fr\>

4.  sea ice

Thierry Fichefet \<fichefet@astr.ucl.ac.be\>

5.  land surface

6.  vegetation

Nathalie de Noblet \<Nathalie.De-Noblet@cea.fr\>

7.  coupling procedure

Olivier Marti \<olivier.marti@cea.fr\>

# Besides atmosphere, ocean, sea ice, and prescription of land/vegetated surface, what can be included (interactively) and was it active in the model version that produced output stored in the PCMDI database?

A.  atmospheric chemistry? no

B.  interactive biogeochemistry? yes, active only for C4MIP

C.  what aerosols and are indirect effects modeled? sulfate aerosols
    only, and first indirect effect only *(TAR = no aerosols)*

D.  dynamic vegetation? yes, but not active in the runs currenty stored
    in the PCMDI database

E.  ice-sheets? extension does not change, thickness changes

# List the community based projects (e.g., AMIP, C4MIP, PMIP, PILPS, etc.) that your modeling group has participated in and indicate if your model results from each project should carry over to the current (IPCC) version of your model in the PCMDI database.

Complet or in progress: CMIP, CFMIP, AMIP, C4MIP and PMIP

*(TAR = CMIP, AMIP, PMIP)*

# Component model characteristics (of current IPCC model version):

A.  **[*atmosphere:* LMDZ-4 model]{.underline}**

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1.  resolution: 2.5° x 3.75° (i.e. 96x71 grid points). Vertical: 19
    levels

*(TAR = 3.6°x5.625°, i.e. 64x50 grid points; vertical: 15 levels)*

2.  numerical scheme/grid

The dynamical part of the code is based on a finite-difference
formulation of the primitive equations of meteorology. The
discretization insures numerical conservation of both enstrophy for
barotropic flows and angular momentum for the axi-symetric component.
Both vapor and liquid water are advected with a monotonic second order
finite volume scheme. The time integration is done with a leapfrog
scheme, with, periodically, a predictor/corector time-step. An
horizontal dissipation operator is applied on both winds and
temperature. For latitudes poleward of 60 degrees, a longitudinal filter
is also applied.

On the vertical, the model uses a classical hybrid -P coordinate. They
are 5 layers below 850 hPa and 8 layers above 200 hPa.

*(TAR = water transport using an upstream scheme. On the vertical, use
of coordinate)*

3.  list of prognostic variables.

    -   temperature

    -   northward and eastward wind components

    -   total water

    -   surface pressure

4.  name, terse descriptions, and references (journal articles, web
    pages) for all major parameterizations. Include, as appropriate,
    descriptions of:

    a.  clouds

The cloud cover f and in-cloud water q_c are deduced from the large
scale total (vapor + condensed) water q and moisture at saturation,
q_sat, using a Probablity Distribution Function P(q) for the
subgrid-scale total water q. This PDF P(q) is described throug a
generalized log-normal function bounded to 0, following Bony and
Emmanuel (2001). The PDF moments are diagnosed interactively from the
condensated water predicted by the convection scheme at the subgrid
scale and from the large scale degree of saturation of the atmosphere.

The indirect effect of aerosols has been introduced using an update
version of the formula \"D\" of Boucher and Lohmann (1995). The
parameters of this formula have been adjusted so that the model
reproduces the decrease of the effectif radius when the aerosols index
increases, as observed by POLDER.

*(TAR = The formulation was based on top-hat probabilituy distribution
functions of total water (Le Treut and Li, 1991). Indirect effect was
not considered)*

Bony, S., and K. A. Emmanuel, 2001: A parameterization of the cloudiness
associated with cumulus convection; evaluation using TOGA COARE data,
J. Atmos. Sci., 58, 3158-3183.

Boucher O,Lohmann U (1995)The sulfate-CCN-cloud albedo effect- a
sensitivity study with two general circulation models. Tellus, 47B,
281-300.

b.  convection

Condensation is parameterized separately for convective and
non-convective clouds. Moist convection is treated using a modified
version (Grandpeix et al., 2004) of the Emanuel (1991) scheme.

*(TAR = a Manabe-Kuo scheme was used)*

Grandpeix, J.-Y., V. Phillips, and R. Tailleux: Improved mixing
representation in Emanuel\'s convection scheme, Q. J. R. Meteorol. Soc.,
in press.

Emanuel, K. A., A scheme for representing cumulus convection in
large-scale models, J. Atmos. Sci., 48, 2313-2335, 1991.

c.  boundary layer

Turbulent transport in the planetary boundary layer is treated as a
vertical diffusion with an eddy diffusivity depending on the local
Ridcharson number (Laval et al., 1981). The formulation of the boundary
layer is very sensitive to the minimum diffusivity in high latitudes.
Specific care was given to this threshold in order to get the right
strength of the polar inversion. The surface boundary layer is treated
according to Louis (1979). The formulation of Smith\'1988 was introduced
to compute the surface roughness length over ocean.

*(TAR = since the TAR, the minimum diffusivity was adusted to have a
better polar inversion, The stability functions were those of Louis
(1982) and Beljaars and Millers (1990) )*

Laval, K., R. Sadourny, and Y. Serafini, Land surface processes in a
simplified general circulation model, Geophys. Astrophys. Fluid Dyn.,
17, 129-150, 1981.

Louis, J.-F., A parametric model of vertical eddy fluxes in the
atmosphere., Boundary-layer Meteorol., 17, 187-202, 1979.

d.  SW, LW radiation

The radiation scheme is the one previously introduced in the model of
European Centre for Medium-Range Weather Forecasts (ECMWF) by Morcrete:
The solar part is a refined version of the scheme developed by Fouquart
and Bonnel (1980) and the thermal infra-red part is due to Morcrette et
al. (1986).

*(TAR = same code)*

e.  any special handling of wind and temperature at top of model

No

f.  other

Effects of mountains (drag, lifting, gravity waves) are accounted for
using a new scheme (Lott and Miller, 1997; Lott, 1999).

For coupling purposes each atmospheric grid box is divided into 4
sub-surfaces corresponding to land surface, free ocean, sea-ice and
ice-sheet. For each atmospheric column, vertical diffusion is applied
independently for each sub-surface, and the resulting tendencies are
averaged.

Lott, F., Alleviation of stationary biases in a gcm through a mountain
drag parametrization scheme and a simple representation of mountain lift
forces, Mon. Weather Rev., 127, 788-801, 1999.

Lott, F., and M. Miller, A new sub-grid scale orographic drag
parametrization: its formulation and testing., Q. J. R. Meteorol. Soc.,
123, 101-128, 1997.

B.  ***[Ocean : OPA]{.underline}***

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1.  resolution

quasi-isotrope tri-polar grid (2 poles in the northern hemisphere, on
over Canada and the other over Siberia. 2° resolution Mercator grid
(i.e. x=y) with enhanced meridional resolution in the vicinity of the
equator and in Med and Red seas (1°)

2.  numerical scheme/grid, including advection scheme, time-stepping
    scheme, vertical coordinate, free surface or rigid lid, virtual salt
    flux or freshwater flux

advection scheme : 2nd order arakawa

time-stepping : leap-frog except for lateral diffusion (forward) and
vertical diffusion (backward)

vertical coordinate : z-coordinate

free surface, freshwater flux

3.  list of prognostic variables and tracers

U, V, T, S, TKE

4.  name, terse descriptions, and references (journal articles, web
    pages) for all parameterizations. Include, as appropriate,
    descriptions of:

All the descrition of the model physics can be found in the OPA
reference manual (Madec at al 1998) available on the web
(<http://www.lodyc.jussieu.fr/opa/Docu_Free/Doc_models/Doc_OPA8.1.pdf>)

a.  eddy parameterization

Isopycnal mixing on tracers (no horizontal background) with a constant
coefficient of 2000 m2/s (Guyliardi et al 2001, Clim. Dyn.) Eddy induced
velocity (Gent and McWilliams 19xx) with a coefficient varying in
function of the growth rate of baroclinic instability (ranges 15 m2/s to
2000 m2/s). Note that the coefficient is set to 0 in the vicinity of the
equator (lengaigne et al JGR 2003)

b.  bottom boundary layer treatment and/or sill overflow treatment

diffusive bottom boundary layer (Beckmann and Dorscher 19xx)

c.  mixed-layer treatment

TKE scheme (Blanke and Delecluse JPO, 1992 + modification Madec et al.
1999)

d.  sunlight penetration

yes with 2 master lengths (Blanke and Delecluse 1992)

e.  tidal mixing

None

f.  river mouth mixing

spread over several grid points (the number depending on the magnitude
of the runoffs)

g.  mixing isolated seas with the ocean

no mixing (Red and Med seas are explicitly connected to the remaining
ocean) . For closed \"seas\" (Black Sea, Great lakes, Caspian Seas) the
mean sea level remain constant, excess (deficit) of water been either
redistributed over the world ocean (Caspian Sea) or in St Laurent river
mouth (Great lakes) or Dardanel strait area (Black Sea).

h.  treatment of North Pole \"singularity\" (filtering, pole rotation,
    artificial island?)

semi analytical tri-polar grid, no singular point in the ocean domain.
based on Madec and Imbar (Clim. Dyn. 1996) and Murray (JCP 1995)

C.  ***[sea ice: LIM]{.underline}***

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1.  horizontal resolution, number of layers, number of thickness
    categories

    -   Horizontal resolution: same as ocean model (2° in longitude and
        roughly 2° cos(phi) in latitude; equations for ice motion and
        transport written in curvilinear, orthogonal coordinates;
        staggered spatial grid of type B).

    -   Number of layers: 3 (1 in snow and 2 in ice).

    -   Number of thickness categories: 2 (level ice and leads).

2.  numerical scheme/grid, including advection scheme, time-stepping
    scheme,

    -   Heat-diffusion equation: fully implicit scheme.

    -   Momentum equation: semi-implicit scheme (combination of a
        modified Euler time step scheme and a point successive
        relaxation procedure).

    -   Advection equations: forward time marching scheme which
        conserves the second-order moments of the spatial distribution
        of the advected quantities.

3.  list of prognostic variables

    -   snow thickness;

    -   ice thickness;

    -   ice concentration;

    -   ice velocity;

    -   internal temperatures of snow and ice;

    -   heat content of brine reservoir.

4.  completeness (dynamics? rheology? leads? snow treatment on sea ice)

    -   Effective thermal conductivity to account for the effect of the
        subgrid-scale snow- and ice-thickness distributions on sea-ice
        thermodynamics.

    -   Surface albedo dependent on the state of the surface (frozen or
        melting), the thickness of the snow and ice covers, and the
        cloudiness.

    -   Parameterisation of leads.

    -   Snow-ice formation scheme.

    -   Viscous-plastic rheology.

5.  treatment of salinity in ice

    -   Constant ice salinity.

    -   Heat reservoir to account for the storage of latent heat inside
        the ice resulting from trapping of shortwave radiation by brine
        pockets

6.  brine rejection treatment

    -   Salt rejected during ice accretion and snow-ice formation is put
        in the first oceanic layer.

7.  treatment of the North Pole \"singularity\" (filtering, pole
    rotation, artificial island?)

    -   Same as ocean model (pole rotation).

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D.  **[land / ice sheets]{.underline}** (some of the following may be
    omitted if information is clearly included in cited references.

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1.  resolution (tiling?), number of layers for heat and water

Surface properties (albedo, roughness\...) and variables (temperature,
humidity) are specific to each of the 12 PFTs (see below). The soil is
decrised into 11 layers for the heat transfer calculations and 2 for
water calculation.

2.  treatment of frozen soil and permafrost

No

3.  treatment of surface runoff and river routing scheme

Yes

4.  treatment of snow cover on land

Snow albedo following Chatita and Le Treut (1994).

5.  description of water storage model and drainage

6.  surface albedo scheme

The albedo values for all PFTs are averaged and combined with the bare
soil albedo.

7.  vegetation treatment (canopy?)

Vegetation is described using the concept of plant functional type
(PFT), and uses 12 PFTs with precribed geographical distribution.
Stomatal resistance and photosynrhesis are calculated for each PFT
separately following Ball et al. (1987), Fargquhar et al. (1980),
Collatz et al.(1992) and depends on CO2 concentration.

8.  list of prognostic variables

9.  ice sheet characteristics (How are snow cover, ice melting, ice
    accumulation, ice dynamics handled? How are the heat and water
    fluxes handled when the ice sheet is melting?)

Snow and ice melting and accumulation are like for the other surfaces.
The only specificity is that ice sheet fraction does not change (no
dynamic), which mean that ice melting does not affect ice thickness and
fraction. When ice or snow are melting, the water is drained toward the
ocean. In order to ensure watter conservation, when snow accumulates
above a threshold, the exeeding snow is drained to the ocean with a 10
years smoothing.

E.  **[coupling details]{.underline}**

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1.  frequency of coupling:

    -   atm-land surface: every time step (30 mn)

    -   atm-ocean and atm-sea-ice: once a day

    -   ocean-sea ice: every oceanic time step

2.  Are heat and water conserved by coupling scheme?

yes

3.  list of variables passed between components:

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a.  atmosphere -- ocean

    -   Net short wave on open ocean

    -   Non solar flux on open ocean

    -   Water budget (precip-evap)

    -   Wind stress over open ocean

    -   Ocean surface temperature

b.  atmosphere -- land

    -   Net short wave

    -   Non longwave flux

    -   water vapor flux

    -   liquide precipitations

    -   solide precipitations

    -   heat flux

    -   surface albedo, rougness\...

    -   surface temperature

c.  land -- ocean

    -   Runoff

    -   Ice sheet melting

d.  sea ice -- ocean

    -   Stress under sea ice

    -   Fresh water flux (concentration/dilution)

    -   Fresh water flux (volume flux for free surface)

    -   Sea ice fraction

    -   Ocean surface temperature

    -   Ocean surface salinity

    -   Surface current

e.  sea ice -- atmosphere

    -   Net short wave on sea ice

    -   Non solar heat flux on sea ice

    -   Solid precipitation

    -   dQ/dT (sensitivity of surface heat flux to surface temperature,
        sens+lat) over sea ice

    -   Wind stress over sea ice

    -   Sea ice fraction

    -   Sea ice albedo (weighted)

    -   Sea ice surface temperature (weighted)

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4.  Flux adjustment? (heat?, water?, momentum?, annual?, monthly?).

No

# Simulation Details (report separately for each IPCC simulation contributed to database at PCMDI):

A.  **[PIcntrl]{.underline}**

B.  Describe method used to obtain initial conditions for each component
    model

The spin-up procedure is the following: The ocean starts from rest with
temperature and salinity set to the values of the Levitus (1982) atlas.
The sea-ice characteristics correspond to a ten years adjustment of the
sea-ice model from a forced ocean-ice simulation. The atmosphere is
initialized from the ECMWF (ERA15) for 1979, January 1st . The land
surface model starts with soil moisture initialized to 300 mm at each
grid point and the snow reservoirs start from zero.

The concentration of the different trace gazes concentration are
prescribed to their pre-industrial values (see below). Starting from
those initial states, a coupled run of 330 years is performed, during
wich the very last smal adjustments of the model have been included.

C.  Radiative forcing agents

For the GHG, we use the same pre-industrial values (circa 1750) as in
PMIP: CO2: 280ppm, CH4: 805 ppb, N2O: 276 ppb, CFC11: 0, CFC12: 0. For
the sulate aerosols, we use the "natural" distribution as computed and
provided by Olivier Boucher. No other aerosols are considered (this is
very clear when looking to the clear sky albedo). The solar constant is
1365 W/m2. All these values are maintained constant.

The aerosols distribution comes from :
http://www-loa.univ-lille1.fr/\~boucher/sres/

A.  **[PDcntrl]{.underline}**

B.  Describe method used to obtain initial conditions for each component
    model

The spin-up procedure is the following: The ocean starts from rest with
temperature and salinity set to the values of the Levitus (1982) atlas.
The sea-ice characteristics correspond to a ten years adjustment of the
sea-ice model from a forced ocean-ice simulation. The atmosphere is
initialized from the ECMWF (ERA15) for 1979, January 1st . The land
surface model starts with soil moisture initialized to 300 mm at each
grid point and the snow reservoirs start from zero.

The concentration of the different trace gazes concentration are
prescribed to their 1980 values (see below). Starting from those initial
states, a coupled run of 70 years is performed.

C.  Radiative forcing agents.

For the GHG, we use the1980 values: CO2: 348 ppm, CH4: 1650 ppb, N2O:
306 ppb, CFC11:280 ppt, CFC12: 484 ppt. For the sulate aerosols, we use
the 1980 distribution as computed and provided by Olivier Boucher. No
other aerosols are considerd (this is very clear when looking to the
clear sky albedo).The solar constant is 1365 W/m2.

The aerosols distribution comes from :
<http://www-loa.univ-lille1.fr/~boucher/sres/>

**[A) 20C3M]{.underline}**

B\) Initial conditions.

Start from first year of PIcntrl run

C)  Radiative forcing agents.

The series of annual values of GHG we used have been gathered by J-F
Royer (CNRM) in the framework of the ENSEMBLES European project. See:
<http://www.cnrm.meteo.fr/ensembles/>

**CO2:** Historical CO2 record from the Law Dome DE08, DE08-2, and DSS
ice cores.

Authors : D.M. Etheridge L.P. Steele R.L. Langenfelds R.J. Francey
Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia
J.-M. Barnola Laboratoire of Glaciologie et Geophysique de
l\'Environnement, Saint Martin d\'Heres-Cedex, France V.I. Morgan
Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania,
Australia

<ftp://ftp.ngdc.noaa.gov/paleo/icecore/antarctica/law/law_co2.txt>

**CH4:** The series for methane CH4 concentrations is generated from the
file ftp://ftp.ngdc.noaa.gov/paleo/icecore/antarctica/law/law_ch4.txt

Etheridge, D.M., et al., 2002, Ice Core, Firn Air and Archived Air
Atmospheric Methane Concentration Data, IGBP PAGES/World Data Center for
Paleoclimatology Data Contribution Series #2002-039. NOAA/NGDC
Paleoclimatology Program, Boulder CO, USA.

Etheridge, D. M., Steele, L. P., Francey, R. J., and Langenfelds, R. L.,
1998, Atmospheric methane between 1000 A.D. and present: Evidence of
anthropogenic emissions and climatic variability J. Geophys. Res. Vol.
103, No. D13, p. 15,979 (98JD00923)

**N2O:** The series is derived from the IPCC values for 1970,1980,1990
and 2000 and from the series of measurements in ice from Machida et al
(1995). The observed values range from 1735 to 1964 (their table 1)

Machida, T., T. Nakazawa, Y. Fujii, S. Aoki and O. Watanabe, 1995:
Increase in the atmospheric nitrous oxide concentration during the last
250 years. Geophysical Research Letters, 22, 2921-2924.

**CFC-11, CFC-12:** The series is derived from the Reconstructed
histories of the annual mean atmospheric mole fractions for the
halocarbons CFC-11, CFC-12, CFC-113 and Carbon Tetrachloride
(http://gaslab.ucsd.edu/pub/cfchist/) described in: Walker, S. J., R. F.
Weiss and P. K. Salameh, Reconstructed histories of the annual mean
atmospheric mole fractions for the halocarbons CFC-11, CFC-12, CFC-113
and carbon tetrachloride. Journal of Geophysical Research, 105, C6,
14,285-14,296, 2000

**Sulfate aerosols:** The aerosols distribution has been provide by
Olivier Boucher (LOA/CNRS)

<http://www-loa.univ-lille1.fr/~boucher/sres/>

Boucher, M. Pham, C. Venkataraman, Simulation of the atmospheric sulfur
cycle in the Laboratoire de Meteorologie Dynamique General Circulation
Model. Model description, model evaluation, and global and European
budgets, Note scientifique de l\'IPSL n. 23, juillet 2002.

O. Boucher and M. Pham, History of sulfate aerosol radiative forcings,
Geophysical Research Letters, 29(9), 1308, 10.1029/2001GL014048, 2002.

**Other variables:** All other variables are kept constant. There are no
natural forcings.

**[A) SRESA2, SRESA1B, SRESB1]{.underline}**

B\) Initial conditions.

Start from end of year 2000 of run 20C3M

C\) Radiative forcing agents.

The series of annual values of GHG we used have been gathered by J-F
Royer (CNRM) in the framework of the ENSEMBLES European project. See:
<http://www.cnrm.meteo.fr/ensembles/>

GHG concentration are those provided by the IPCC (for CO2, Bern-CC
reference model is used).

Sulfate aerosols ate those computed by Olivier Boucher (LOA/CNRS)

<http://www-loa.univ-lille1.fr/~boucher/sres/>

**[A) Commit]{.underline}**

B\) Initial conditions.

Start from end of year 2001 of run 20C3M

C\) Radiative forcing agents.

Same as year 2000 of run 20C3M

**[A) 1%to2x and 1%to4x]{.underline}**

B\) Initial conditions.

Start from first year of PIcntrl run

C)  Radiative forcing agents.

Initial value of CO2: 286 pp. CO2 increase 1%/year during 70 years
(1%to2x) or 140 years (1%to4x), then CO2 concentration is kept constant
with a value of 574 ppm (%to2x) or 1152 (1%to4x).