Radiative energy balance for this atmospheric layer requires that (realclimate.org)
Nevertheless, the results described here provide key evidence of the reliability of water vapor feedback predicted by current climate models in response to a global perturbation in the radiative energy balance.» (realclimate.org)
Since much of this is an indirect process through the thermohaline circulation that would seem to act like ice, it would also not be part of the process by which equilibrium was reached in the radiative energy balance calculation. (realclimate.org)