Global warming exists. Anyone who denies that is also a moron. But it's certainly not manmade.
I don't get the focus on whether or not the warming is anthropogenic. Should we ignore all problems that we didn't make?
Supposing that the warming isn't primarily anthropogenic, there's still plenty of reason to believe that the greenhouse gases we're adding are making it worse, and in fact we can even make some reasonable estimates of how much worse they're making it.
At the end of the day, you'd really better hope that you're wrong about our ability to modify the climate. Because the current climate of Earth is not typical. In fact, there isn't really a "typical" climate for the planet. Ice core histories show us that it swings between much hotter than it is, and much, much colder (by "colder", think "equatorial oceans frozen 30 feet deep for millenia"). Both extremes will be unpleasant for us, and I say "will", not "would", because it's gonna happen. When? We have no idea. We know that climate changes can happen very rapidly (couple of decades), even without an obvious precipitating event (big meteor, supervolcano eruption, etc.), and that they come at apparently-random intervals.
So if we want this planet to be nice for us long-term, we'd better learn to engineer our climate. Or get even better at adapting our local environment. Or both.