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6ka Experimental Design

Boundary conditions

Summary of 6ka boundary conditions

PMIP3/CMIP5
Orbital parameters	[ ecc = 0.018682 ] - [ obl = 24.105° ] - [ peri-180° = 0.87° ]
Date of vernal equinox	March 21 at noon
Trace gases	[ CO2 = 280 ppm ] - [ CH4 = 650 ppb ] - [ N2O = 270 ppb ] - [ CFC = 0 ] - [ O3 = same as in CMIP5 PI ]
Aerosols	Same as in CMIP5 PI
Solar constant	Same as in CMIP5 PI
Vegetation	prescribed or interactive as in CMIP5 PI
Ice sheets	Same as in CMIP5 PI *
Topography and coastlines	Same as in CMIP5 PI *

* Sensitivity experiments will be proposed as part of a working group to test the uncertainties due to the remnant ice-sheet. If you are interested in participating to this working group contact Pascale Braconnot

Vegetation

The vegetation should be treated as in the CMIP5 PI experiment. The reason is that in CMIP5 we test the version of the model used for future climate projections. Since OA and ESM models will be considered, depending on the model used the vegetation will be

prescribed to PI (which means both vegetation types and LAI are prescribed )

Prescribed to PI with interactive LAI (models with interactive carbone cycle, but no vegetation dynamics)

Computed by the model (models with dynamic vegetation)

For Earth System Models with interactive carbon cycle

The simulations should be forced by the prescribed 6ka CO2 concentrations. Please use the same protocol as in CMIP5 to store the diagnostic carbon fluxes and the variables needed for PCMIP (see pcmip Project and CMIP5)

Insolation

Note that insolation should follows PMIP requirements. Please check it carefully using the following tables (6ka BP insolation tables)

Check carefully the date of the Vernal equinox, because it has implications when we compare paleo and PI seasonal cycle

6ka for groups only running PMIP3 experiments

If you only run PMIP3 experiments we recommand that you follow CMIP5 (see taylor_cmip5_dec31.pdf) or PMIP2 (PMIP2 web site) for the PI simulation

Initial conditions

PMIP3	Alternative solution
Initial conditions	Branch off PI after adjustment	Same as in PI
Model spin up	Same as in PI

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