Description of Simulations for the IPCC AR4

Meteorological Research Institute

10 Febrary 2005

1. PIcntrl

   The “PIcntrl” is pre-industrial simulation used for the reference to the historical (20C3M) and SRES experiments, and also provides initial states for the “20C3M”.
   The initial state of “PIcntrl” is taken from the final state of a 450-year pre-industrial spin-up (PIspup) which initiated from the end of present-day spin-up run (428 year length, see comments on PDcntrl). The PIspup is fully coupled mode time integration, and is long enough so there is little climatic drift in PIcntrl at least in the upper ocean.
   The forcing agents of the “PIspup” and “PIcntrl” experiments, greenhouse gases, sulfate aerosol direct effects and solar forcing, are fixed at levels of year 1850 (CO2 = 290 ppmv, CH4 = 792 ppbv, N2O = 285 ppbv, solar constant = 1366.0 Wm?2, and sulfate aerosol from natural source).
   
   
   

2. PDcntrl
   

   The “PDcntrl” is a present-day control simulation, and is used for reference to the 1%/year CO2 increase experiments (1%to2x and 1%to4x).
   The initial state of the “PDcntrl” is taken from the end of the present-day spin-up (PDspup) of 428-year length, which is initiated from Levitus climatological ocean state. The “PDspup” is executed with fully coupled mode, and consists of a 334 year restore stage and a 95 year flux-correct stage. In the former stage, the temperature and salinity is restored to the observational climatology. In the latter stage, the ocean is driven by atmospheric fluxes and flux correction that is made from the climatology of restoring terms in the last part of the restore stage.
   The forcing agents of the “PDspup” and “PDcntrl” experiments, greenhouse gases, sulfate aerosol direct effects and solar forcing, are fixed at the ‘present-day’ (CO2 = 348 ppmv, CH4 = 1650 ppbv, N2O = 306 ppbv, solar constant = 1367.0 Wm?2, sulfate aerosol from natural and anthropogenic source).

   
   
   

3. 20C3M
   

   This experiment consists of 5-member ensemble simulations of the 20th Century climate (starting from mid-19th Century).
   The initial state of each member simulation is taken from the different states of the pre-industrial control (PIcntrl) experiment at 1, 51, 101, 151, and 200 years. The forcing agents of the experiment are the historical record of (or estimated) greenhouse gases (CO2, CH4, N2O and CFCs), sulfate aerosol direct effects, volcanoes and solar forcing.
   

   
   
   

4. SRESA1B
   

   This experiment consists of 5-member ensemble simulation of future climate projection for IPCC SRES-A1B scenario.Each member simulation starts from the state of respective year 1990 in the “20C3M” ensemble, although the “20C3M” are extended until year 2000.
   The forcing agents of the experiment includes greenhouse gases (CO2, CH4, N2O) and sulfate aerosol direct effects, which are based on IPCC SRES-A1B for 1990-2100.
   One of the members (run-1) is extended until 2300 with holding the concentrations fixed at 2100 level, and the rest of the runs end at 2100.
   

   
   

5. SRESA2
   

   This experiment consists of 5-member ensemble simulation of future climate projection for IPCC SRES-A2 scenario.
   Each member simulation starts from the state of respective year 1990 in the “20C3M” ensemble, although the “20C3M” are extended until year 2000.
   The forcing agents of the experiment includes greenhouse gases (CO2, CH4, N2O) and sulfate aerosol direct effects, which are based on IPCC SRES-A2 for 1990-2100.
   
   
   

6. SRESB1
   

   This experiment consists of 5-member ensemble simulation of future climate projection for IPCC SRES-B1 scenario.
   Each member simulation starts from the state of respective year 1990 in the “20C3M” ensemble, although the “20C3M” are extended until year 2000.
   The forcing agents of the experiment include greenhouse gases (CO2, CH4, N2O) and sulfate aerosol direct effects, which are based on IPCC SRES-B1 for 1990-2100.
   One of the members (run-1) is extended until 2300 with holding the concentrations fixed at 2100 level, and the rest of the runs end at 2100.

   
   
   

7. 1%to2x

   This experiment simulates transient climate response to 1%/year increase of CO2 concentration.
   The initial state is identical to the beginning of “PDcntrl” simulation, which is taken from the end of the 428-year present-day spin-up (PDspup).
   The CO2 concentration increases (starting from 348 ppmv) with 1%/year compound rate and reaches doubled (696 ppmv) at 70th year, and is fixed doubled after that. The other forcing agents are same as in the “PDcntrl” simulation (e.g., CH4 = 1650 ppmv, N2O = 306 ppbv, solar constant = 1367.0 Wm?2 and sulfate aerosols of the ‘present-day’ level).
   
   
   

8. 1%to4x
   

   This experiment simulates transient climate response to 1%/year increase of CO2 concentration.
   The initial state is identical to the beginning of “PDcntrl” simulation, which is taken from the end of the 428-year present-day spin-up (PDspup).
   The CO2 concentration increases (starting from 348 ppmv) with 1%/year compound rate and reaches doubled (1392 ppmv) at 140th year, and is fixed quadrupled after that. The other forcing agents are same as in the “PDcntrl” simulation (e.g., CH4 = 1650 ppmv, N2O = 306 ppbv, solar constant = 1367.0 Wm?2 and sulfate aerosols of the ‘present-day’ level).

   
   
   

9. Slabcntl

   This simulation is a control simulation with the slab ocean model, which is used for reference to the equilibrium response experiment (2xCO2).
   Starting from the initial state with observed SST climatology (Levitus, 1994), the model is spun-up with coupled mode by restoring the slab temperature to the observed SST climatology to make ‘Q-flux’. By using the ‘Q-flux’ the model is run long enough (250 years) to reach a complete equilibrium and to produce stable statistics for the sampling period of the last 50 years.
   The forcing agents are same as in the “PDcntrl” simulation (CO2 = 348 ppmv, CH4 = 1650 ppbv, N2O = 306 ppbv, solar constant = 1367.0 Wm?2 and sulfate aerosols of the ‘present-day’ level).
   
   
   

10. 2xCO2

    This is a simulation of equilibrium response to an instantaneous doubling of CO2 (696 ppmv) with the slab ocean model.
    The initial state is identical to the “Slabcntl” simulation. It’s run is long enough (250 years) to reach a complete equilibrium and to produce stable statistics for the last 50 years for the sampling period.
    The other forcing is same as in the “Slabcntl” experiment (CH4 = 1650 ppmv, N2O = 306 ppbv, solar constant = 1367.0 Wm?22 and sulfate aerosols of the ‘present-day’ level).
    
    
    

11. Commit
    

    This simulates committed climate change by the forcing in the past, assuming all the anthropogenic forcing is fixed at year 2000 levels (CO2 = 393.7 ppmv, CH4 = 1738 ppbv, N2O = 315.5 ppbv, solar constant = 1367.0 Wm?2, and sulfate aerosols at the year 2000 level.
    The initial state is taken from the end of the run-1 of “20C3M”.
    
    
    

12. AMIP
    

    This is an ‘AMIP type’ simulation with the atmospheric component of the MRI-CGCM2.3.2 which is identical to other IPCC experiments. The atmospheric initial state, anthropogenic forcing and solar forcing are same as in the “PDcntrl” experiment (CO2 = 348 ppmv, CH4 = 1650 ppbv, N2O = 306 ppbv, solar constant = 1367.0 Wm?2 and sulfate aerosols of the ‘present-day’ level).
    The simulation period is through 1978 to 2002, for which the ‘AMIP II SST and sea ice boundary condition data set’ is used.