We have discussed that persistent question here before: what word to use when talking about people who simply refuse to acknowledge in the slightest the rather solid case for the theory of anthropogenic global warming.
I was thinking it would be worth a very in depth and lengthy post. But I gratefully bow to Greenfyre’s excellent essy on the subject which you can (and should IMO) read in full right here.
He makes all of the points I would have plus a good deal more.