The stream one simulations make use of the methodology and the forcings that were defined for the CMIP3 simulations contributing to the IPCC AR4 assessment (http://www-pcmdi.llnl.gov/ipcc/about_ipcc.php)

In order to insure the consistency of the simulations in RT2A the following set of coordinated simulations has been produced.

1) Historical simulations:
The historical simulations were started from a balanced initial condition obtained in a long control preindustrial integration with fixed forcings corresponding to the observed values for the year 1860
-    A first historical simulation with observed anthropogenic forcings only (greenhouse gases, aerosols and ozone concentrations) over the period 1860-2000.
-    A second historical simulation similar to the previous simulation, but with in addition the observed natural forcings (solar and volcanic)

2) Future scenarios:
The scenarios were started from an initial condition obtained for year 2000 in the first historical simulation with anthropogenic forcings in order to insure continuity
-    The scenarios over the 21^st century and beyond use only anthropogenic forcings (GHG, aerosols and ozone) defined for the CMIP3 simulations from impact assessment models with the different SRES scenarios chosen for the AR4
o    A2
o    A1B
o    B1