While the media are busy hyping the melting of the Antarctic glaciers, they're conveniently ignoring the ice elsewhere in the world, which in many cases is growing rather than shrinking. I rather doubt either an ice age or global warming is going to kill us any time soon. The biggest chance for disaster is that some nut will get his hands on a few nukes and start blowing things up, which belongs more under the category of Apocalypse than anywhere else.
Or we could be impacted by a rock the size of a small moon. One can never predict these things, otherwise they wouldn't be disasters, would they?