Not sure, but I believe there are nuke-proof bunkers that could secure humanity if such an event were ever to occur.

General "Buck" Turgidson: Mr. President, we must not allow a mineshaft gap!"

President Merkin Muffley: [Turns to Strangelove] You mean people could actually stay down there for a hundred years?

Dr. Strangelove: It would not be difficult, Mein Führer. Nuclear reactors could - heh, I'm sorry, Mr. President - nuclear reactors could provide power almost indefinitely...

> Dr. Strangelove: It would not be difficult, Mein Führer. Nuclear reactors could - heh, I'm sorry, Mr. President -

This makes much more sense after learning the story of Werner von Braun (via Tom Lehrer's song)

Fully appreciating that movie requires a lot of knowledge of history.

Deep deep underground with lots of canned food, diesel and light that can simulate sunlight... Think Zion in the matrix :)

More like Howey's "Wool" (Silo Series[1]).

[1]: http://en.wikipedia.org/wiki/Silo_(series)