Where you attend school? Is it a conservative college/uni? What topic is the professor supposed to be covering? (What class, in other words?) Trump doesn't believe in global warming either.... All I know is something weird is going on with the weather, and if we humans are affecting it, then I think we need to figure out why and stop doing it!

Maybe ask some questions such as what does he think is causing the climate change and if he's off topic, then try to bring him back to the subject at hand. I think we all have our soap-box topics, but good professors don't veer much from their subject matter. (Is this going to be on the next test? )

I doubt you'd be able to change his mind. Perhaps he doesn't have both oars in the water.

(I was a college professor, off and on for 20 years.)