I endorse this explanation, and prediction, from Crispin Sartwell:
as i've said, the insane jackup of rhetoric with regard to global warming, “the greatest crisis the species has ever faced,” the death of the planet, etc, is the secular humanist liberal apocalypse. it's a sheer competition for who's most dire, most obsessed, and who's more unanimous than whom. it's the flood, complete with the reasons: our moral culpability. i predict this: when obama is elected, liberals will feel better about themselves and the probable verdict of cosmic judgment, and they'll tone down the eschatology, the ranting cant.
Climate eschatology really is the ultimate in big lie crisis politics. The far-left has failed so comprehensively to make the case for its vision of society and economy that the only thing left to do is to brazenly and repeatedly assert that the world will literally collapse unless we implement this otherwise indefensible vision.
this piece, for example, has no motivation except that some website claims that we've got a hundred months until our incineration becomes inevitable. in other words, it's not about science; it's not even about the columnist's interesting moves in an argument, his poetry or rhetoric or something: it's simply reporting that someone else has jacked up the volume, yet again.
I think the point is that the clock really is ticking. If we don't “do something” soon, we'll probably see that we don't really need to do anything really dramatic, and then the window for radical social change will be closed. So I expect the volume to get much louder.