NARCCAP includes two timeslice experiments. As with the regional models, the timeslice experiments are run for the current (aka "historical") conditions (1969-2000) and the future (aka "scenario") conditions (2039-2070).

In the timeslice experiments, the atmospheric component of an AOGCM is run without the full-coupled ocean component of the model. Instead, the boundary conditions for sea surface and ice for the historical run are based on observational data, and boundary conditions for the scenario run are derived by perturbing the same observed sea-surface temperature and ice data by an amount based on the results of a lower-resolution run of the full AOGCM.

Because the coupled ocean model is omitted, the computational requirements of the simulation are much lower and the atmospheric model can be run at a higher resolution. The NARCCAP timeslice experiments are run at 50-km resolution, the same as the regional climate models.

It's called a 'timeslice' experiment because it only simulates two slices of time, one for the present and one for the future, and skips over the time between them, rather than simulating the full transient all the way from the beginning of the present period through to the end of the future period.

The first NARCCAP timeslice uses the AM2.1 model, which is the atmospheric component of the GFDL GCM. This experiment was run by Isaac Held, et al, at the GFDL. Data from this experiment has been archive and published and is available now through the Earth System Grid for registered NARCCAP users.

The second NARCCAP timeslice uses the NCAR CAM3 model, which is the atmospheric component of the CCSM GCM. This experiment was run by Phil Duffy at LLNL. The experiment has been run, and the data is currently being post-processed and is in the initial stages of QC and archiving.