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.
When I pointed out to him that scientists actually used evidence to support their arguments, he said that since this evidence was out of the scope of his understanding, it was equally as valid as the spiritual experiences of a religious person claiming that his experiences were "evidence" of the existence of God. Thus, according to him, the conclusions of a religious fanatic would exactly be the same as the conclusions of scientists, from a rational person's point of view.
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?