The problem is that practically all the climate models used so far are wrong. From a scientific viewpoint it is just an unproven theory, because its predictions are either not proven (because we're waiting the results) or proven wrong.
In other words, it's a scientific hypothesis. That doesn't mean it's wrong. That doesn't mean it's likely to be wrong. It only means that we don't have a bunch of extra Earths lying around with which to conduct repeatable experiments that would confirm the predictions of the hypothesis. The hypothesis might be wrong, even if the likelihood of its being wrong is very low.
By the way, science is never proven. Proofs are for mathematicians.
Human-made global warming: every sensible man should consider this a wild speculation at the moment
Uh, no, a sensible, scientifically literate person should consider it a valid scientific hypothesis. Sure, it might be completely wrong, but it probably isn't.