Yes, he was downvoted: for denying climate science - nothing personal.
I think it's appropriate to downvote posts/comments that deny well-established scientific or historical facts, examples include Holocaust denial (see also here), Climate science denial (see also here), Flat eath etc.
Also I prefer to avoid discussions with deniers about the topics of their denialism, because it gives the impression there is a debate where in fact there is no debate. While some deniers are just victims of disinformation, lack education or intelligence (or suffer from some mental condition), others do it to further a political agenda or for the purpose of trolling.
Recommended reading (in particular the part about irrationality) related to this issue is this post.
Usually I don't explain my downvotes in such detail - here I do it because @diabolika asked.
RE: What is Evil? (Bloody Fields)