fallacy type

Mr.X told me that global warming does not exist and we should not worry about it. Since Mr.X is my art teacher, iam pretty sure we can trust him.

This is the appeal to false authority, which makes it a weak argument for anything not related to art. I agree fully with Dr. Bo. Beyond that, the evidence for global warming is overwhelming. And thus this is also factually incorrect.

This would be an Appeal to False Authority . It has not been established that Mr. X is an authority in the topic. He might be, but again, it has not been established.