Coupling grid applications developed by different teams requires code modification and high S/W engineering effort. In the Ensemble methodology message passing components are developed separately as independent modules, and applications, whether regular, irregular, SPMD or MPMD, are composed from these modular components, without any code modification. We demonstrate by developing two downsized atmospheric and ocean components, which may run on their own or coupled together (limate model) in any configuration depending on geography or other design issues.