I believe that this claim refers to some of the more extreme climate alarmists. Claims that at least sound like this have in fact been made.

yeah, i know that's what it refers to, but it is a straw man. Nobody actually thinks the world is going to literally end in that short of a time frame, and the existence of claims vaguely like this still don't mean its a widely held belief.

Well, if it's not widely held, then it shouldn't be as widely said. Saying it when everybody knows it's not true just makes you look like a nut case who's lost touch with reality. People who make such claims do their cause more harm than good.