Or, in this case, by their fruitcake ideas.
I'm not even sure all these wingnut Republicans really truly believe global warming is natural. Oh, sure, Michele Bachmann is vacuous enough to believe it, and so do many of the others, especially the idiots who've gone to fundie schools and have not even a passing acquaintance with science, at least not as anything other than a source of evil-ution and a punching bag for bullshit fundamentalist denial.
But surely some of these deniers are intelligent enough to understand the data. Those are worse than the sincere deniers. They are simply hypocrites who know what they have to say to be viable Teapublicans.
The fact that success in one of the two main American political parties requires a declaration of one's own stupidity - because so many of its base voters have chosen denial as their core epistemic principle - is truly frightening and a far greater existential threat than terrorism could ever be.