A nuclear attack may have started now.

And now, and now, and now. The reality of the situation is that from launch of missiles carrying a nuclear payload, many primary strike locations (which would likely be airburst to disrupt communications and electronics) would be hit within 15 minutes. Civilians would likely not be informed, or would simply be told to shelter in place. Looking at the declassified primary strike plans for both NATO and Russia, we can safely conclude that in the event of an all-out nuclear attack (which is the most probable outcome of any nuclear engagement) we would neither be equipped nor informed on how to survive.

Before you conclude that such an eventuality is distant, I would ask you to look again at instances of "close-calls" between states in which nuclear weapons were involved. The world has come to the brink of extinction several times. When will our luck run out? Did it run out 10 minutes ago?