Quoted from: Kiehl, Jeffrey T., and Peter R. Gent. "The community climate system model, version 2." Journal of Climate 17, no. 19 (2004): 3666-3682.  https://doi.org/10.1175/1520-0442(2004)017%3C3666:TCCSMV%3E2.0.CO;2 

The first version of the Climate System Model (CSM1) was developed mainly at the National Center for Atmospheric Research (NCAR) and was released in 1996. A 300-yr fully coupled control simulation was performed that had a stable upper-ocean, sea ice, atmosphere, and land climatology. This was the first such simulation obtained without the use of flux adjustments (see Boville and Gent 1998). There was a second release in 1998 that improved the software and corrected the air–sea ice drag coefficient, which was much too large in the original code. CSM, version 1.3 (CSM1.3), released in 2000, contained physics improvements in all components for use in transient climate simulations (see Boville et al. 2001).

Since then, work has continued to develop a second version of the model with the involvement of many scientists from both the academic community and other national laboratories. In recognition of this fact, the new model has been renamed the Community Climate System Model, version 2 (CCSM2). Completely new land and sea ice components have been developed that are briefly described below, and the ocean component has a new base code. One reason for these changes and choices is that CCSM2 now runs efficiently on massively parallel computers, while the first version did not. A considerable amount of software engineering work has been done on the CCSM2 components and the coupler to make the code portable and efficient on a variety of platforms and easier to understand and run. Much of this work has been done in collaboration with several scientists at institutions funded by the Department of Energy. The CCSM2 project is jointly funded by the National Science Foundation and the Department of Energy.

The CCSM2 components are briefly described in section 2. Sections 3 and 4 describe the control simulation mean climatology and interannual variability. A discussion and conclusions are given in section 5.