There is no bulk transport
of molecules because the gas is hydrodynamically stable by construction so no parcel
of air experiences a net upward or downward force, begins at
rest, and according to Our Friend Newton, remains at
rest.
Either
of these GHGs will gain energy if they absorb IR from the ground (or from GHGs in the atmosphere), but then when they collide with other
molecules (almost always N2 or O2) they will give away that extra energy until they are at the same average energy as the
rest of the
air.