The first phase of GeoMIP simulations involved four experiments dealing with solar dimming (G1 and G2) and stratospheric aerosol injection (G3 and G4). All of these experiments are described in more detail by Kravitz et al. (2011).
During the course of simulation, modeling groups requested additional information regarding how the simulations should be conducted. We have created an Additional Specifications Document that provides more of these important details.
Official GeoMIP policy for data use is that if you use output from a particular model within a certain time window, you must contact the modeling group and offer them a chance to contribute as authors. Each modeling group is well posed to understand its model and the intricacies of performing the GeoMIP experiments, so their perspectives will undoubtedly be useful. The modeling groups can be found on the Participants page. For the original GeoMIP experiments G1, G2, G3, and G4, this window of time has expired, and all GeoMIP output is now freely available for use without consultation with the modeling groups.
One additional experiment proposed by Simone Tilmes and Mike Mills is G3solar. This experiment has the same specifications as G3 but uses solar dimming instead of stratospheric sulfate aerosol injection. The purpose is to compare the effects of the two different representations of solar geoengineering. G3solar is an unofficial experiment in GeoMIP. For modeling groups wishing to participate in this experiment, please see the data page.