I was arguing with a climate change denier. 

He said that appealing to a scientific consensus, even one as overwhelming as 97%, is fundamentally an appeal to authority fallacy and hence invalid. He said that it was no different than appealing to a religious body on the state of the universe or the existence of a god. 

In response, I pointed out to him that an appeal to authority was only fallacious if it referred to an "authority" who wasn't actually a qualified expert on the topic being discussed. Hence, deferring to the consensus of qualified climate scientists was logically valid in a discussion about climate change. 

To this, he said that the term *qualification* is itself ambiguous. To believe a person is qualified would be to believe that the body giving out the qualifications (e.g. an university) was actually doing its job correctly. This belief itself would be predicated on a form of faith, which, in his view, is irrational. According to him, this faith would literally be the same as putting faith in the Church that the Pope is a messenger of God. 

He also said that the selection bias that would exist in the climate science community would invalidate any arguments they might make. 

Now, intuitively, I know that his whole argument was incredibly idiotic. But I seem to have no way to actually refute his argument in the scenario of rational discussion, without introducing the concept of trust/faith in the scientific community and the qualifying bodies. 

It is incredibly unlikely that I will encounter such an out-of-left-field argument from anyone else. But if I do, what arguments should I arm myself with?