Warming: Decreased clouds allow more IR, visible, and UV rays to penetrate lower, get absorbed, and be re-reflected back by the (increased) water vapor still present.
Of course parameterization for cloud cover is included in GCMs!
But my question was about the energy balance, if the radiative forcing (IPCC definition) is 2 W/m2, how is that excess energy expressed, if not as atmospheric heat (sensible/latent)?