There's been a bunch of mini-dooms along the way as well, everything from y2k causing planes to drop from the sky to terrorists attacking cities more frequently

There's been a bunch of mini-dooms along the way as well, everything from y2k causing planes to drop from the sky to terrorists attacking cities more frequently. I think it's in peoples nature to mentally take trend lines straight up, or even exponentially up. So, if there were x nuclear warheads in 1987, then they assumed it would be 100 * x in 2012. The same pattern is at work with the climate now, as you've pointed out. Those who speak of the largest catastrophes get the most airtime, and it's a self-reinforcing cycle. Any room full of teenagers will inevitably predict the world will be uninhabitable by their 40th birthday, when in reality it will probably be much the same.