Read the argument
There's no question the creationism and intelligent design are screwball concepts, but when you parse, AGW is just about as screwy as ID. So, while some of his ideas may be cockeyed, not even a majority of biologists can actually talk coherently about evolution with descending into ontological confusion. The question is not whether all of his ideas are screwy, just if this one is. Spencer's arguments are directed at recognized problems in existing GCMs having to do with atmospheric moisture, cloud formation, etc. He concludes sanely that satellite evidence strongly suggests that there really is no "missing" energy. That guarantees an attack from AGW theorists because implies they can't do their sums properly.
He isn't the only scientist to argue so either. In fact, contrary to the media-provided impressions one might develop, there is no general agreement among atmospheric scientists that a "greenhouse effect" theory is even necessary to understand climate, or in fact to explain earth's weather and average climate. There are physicists that are quite blunt in pointing out that the "physics" of current climate theory should mean that perpetual motion machines are possible. It might be best to regard the arguments and logic and not the men. We might actually form a consensus about what we don't know.