From a scientific perspective there is some indication that a nuclear war could deplete the earth's ozone layer or, less likely, could bring on a new Ice Age - but there is no suggestion that either the created order or mankind would be destroyed in the process.
“The only thing we don't do together is get in front of an actor and show any indecision at all about what we think. We don't always agree, so we meet privately, then one or the other will approach the actor.”