Correct, this is not a theory, like the theory of gravity.
It is an attempt to understand the steady increase in global temperatures over the years. There's plenty of refutable science at work. Researches uncover trending data of global temperatures. Other researchers could show problems in approach, or show data that disagrees.
Modelers make predictions of change over the course of years. The accuracy of their predictions speaks to the quality of the models.
Fundamentally, though we have a problem. It would be great if we had two planets. One where we toss as many greenhouse gases into the atmosphere, and another where we do everything the super enviro-crazy vegan wants us to do. Then a hundred years later, we compare temperatures. The problem is that we don't have spare planets to play with. So we have a relatively high stakes game where we work with models, and do a lot of falsify-able detailed science to help inform those models. Only in the models can we run the data for 100 or 1000 years quickly and without much consequence.
Oh, and anyone who would blame Bush for climate change is a nut job. Most of the damage done so far was done before his birth, while he was a child, or while he was a drunk and playboy. It's hard to blame him for any of that. But to argue only against the nut jobs is strawman bullshit. You're right though, czars aren't going to help. A carbon tax might (and might help balance budget or free money for other tax cuts). Helping China build cleaner coal plants might (and would be cheaper than retrofitting ours). But yeah, czars won't help much.