One crude answer is money. The fossilfuel industry has deep wells of it—no business in history has been as profitable as finding, refining, and combusting coal, oil, and gas. Six of the ten largest companies on earth are in the fossil-fuel business. Those companies have spent some small part of their wealth in recent years to underwrite climate change denialism: Jane Mayer’s excellent New Yorker piece on the Koch brothers is just the latest and best of a string of such exposés dating back to Ross Gelbspan’s 1997 book The Heat Is On.

Read the comments on one of the representative websites: Global warming is a “fraud” or a “plot.” Scientists are liars out to line their pockets with government grants. Environmentalism is nothing but a money-spinning “scam.” These people aren’t reading the science and thinking, I have some questions about this. They’re convinced of a massive conspiracy.

What missionaries and militaries have in common is that they have to deal with reality. In fact, that was always the trump card of conservatism: It refused to indulge in sentimentality and idealism, insisting on seeing the world as it was. But, at the moment, it’s the right that is indulging in illusion, insisting, fists balled up and face turning red, that the reports from scientists simply can’t be true.

I understand why those reports are bad news. Dealing with climate change really will be the most difficult thing we’ve ever done. (Too many progressives are clinging to their own illusion that we can simply rip the internal combustion engine out of our economy, toss in a windmill, and carry on as before.) The only thing harder than dealing with it will be not dealing with it and inheriting a world radically changed.