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4. Description of the simulations

4.1 Initialization

4.2 Duration

Simulation

All "C" injection simulations (C800, C1500, C3000) begin at year=2000.0 and will be continued until year 2500.0. Thus, the duration of the C simulations is 500 years. Conversely, the "E" simulation (E1500) begins in year=1765.0 and ends in year=2500.0; thus its duration is 735 years.

Injection Period

In all simulations, artificial sequestration of anthropogenic CO2 will occur for 100 years, beginning on the first timestep of the year 2000 (Jan. 1) and continuing until the last timestep of the year 2099 (Dec. 31). Each year during the 100-yr injection period, 0.1 Gt C is injected at each site, for a total of 0.7 Gt C/yr for the global ocean (seven sites). This amount corresponds to the emissions necessary to produce 350 GW by coal-fired plants or 700 GW by gas-fired plants. Meanwhile, 0.6 Gt C/yr should be removed from the fossil fuel emissions to the atmosphere. The difference between the injection and the removal from fossil fuel emissions is due to the 14% cost penalty (see section Conservation equation for the atmosphere)

4.3 Atmospheric boundary conditions

The atmospheric boundary conditions depend on the chosen scenario:

Standard scenario (C1500) and other C runs (C3000 and C800)

Atmospheric pCO2 follows the IPCC S650 stabilization scenario. Atmospheric pCO2 stabilizes to 650 uatm at year 2200.

The ASCII file pco2.s650.dat ( Fig. 2) provides mid-year values of the atmospheric pCO2 that must be prescribed in the IPCC S650 cases (C800, C1500, and C3000). See concent.f and related technical notes in Section 3). Concentrations from pco2.s650.dat are to be imposed only in the second and third atmospheric boxes B(2) and B(3). Conversely, in the first atmospheric box B(1), atmospheric pCO2 must be held to its preindustrial value 278 uatm.

Emissions scenario (E1500)

We require a smooth emissions scenario to avoid needlessly complicating analysis. Thus we avoid using historical emissions and IPCC future scenarios. Instead we rely on total emissions deduced from an IPCC S650 "concentration" run in one model. The choice of the model is not critical for our objectives of model comparison. We have chosen to use deduced emissions from the S650 concentration run with the HILDA model because (1) HILDA's deduced emissions are already available from 1765 to 2500, (2) its emissions will produce smooth atmospheric CO2 (and time deriviatives) in the other OCMIP models, and (3) HILDA has been used as the IPCC reference model. For further information about the HILDA model, see http://www.climate.unibe.ch/~joos/model_description/model_description.html.

The ASCII file emissions.dat ( Fig.3) provides values of the total emissions every half year that must be prescribed in the Emissions scenario (E1500). These values should be interpolated at each time step of the model. See emit.f and related technical notes in Section 3. This emission scenario is prescribed in the second and third atmospheric boxes B(2) and B(3). Conversely, in the first atmospheric box B(1), there are no anthropogenic emissions.


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