The oceans have been absorbing the heat from the atmosphere, yielding the flat trend in atmospheric temperatures. The total energy in the system is increasing.
Intuitively, adding greenhouse gasses to the atmosphere should, in isolation, increase energy in the system. But what if we really were heading for a new ice age as some feared in the 70s. And the only thing that prevented us from freezing to death, was the concerted effort of those notoriously concerned and altruistic SUV drivers taking one for the team, by revving up their Hummers.
As for the ice age business, climate modeling from 40 years ago is an entirely separate thing compared with today's climate modeling. The advances we've made in model resolution and understanding the physics is quite compelling.