[jraines]

You are correct about this. Without getting into probabilities of the different outcomes resulting from action or non-action on climate change, I'd recommend the video someone posted lower down in this thread.

The weight given to an outcome in considering it in decision making would be the probability x magnitude (+ or -). So on your drive home the risk of death might not affect your decision to make the drive, if you had to drive across Johannesburg or Kuala Lumpar, you might consider taking a cab.

So even while the probability that the Country A would survive a nuclear first strike with the capability to retaliate was quite low -- the magnitude of the outcome from its doing so was enough to dissuade Country B from taking that chance.

To the other commenter below -- just google 'prisoner's dilemma' or 'Nash equilibrium' for some sources to get you started on game theory.

Note: I'm not claiming to be an expert on game theory by any means. I'm recounting the Mutually Assured Destruction example from an economics class's subsection on game theory and would be happy if someone wanted to prove me wrong or elaborate on the subject.