I'd love to see Jonathan Schell's seminal work on nuclear winter (The Fate of the Earth) get the publicity it had when it was originally released.

It doesn't matter how many of their weapons would work or not work. All it would take for a nucelar winter to wipe out most human life on the planet is a few weapons to ignite. A nuclear winter would then overwhelm the atmosphere and destroy most plant life and anything that subsists on said plant life.

Mother earth would eventually rally. And humans would, rightly, be replaced as the dominant species.