Part 6 of 6:

Whether you believe that severe outcomes are certain, merely probable or very improbable if our behavior does not change, you are forced by a proper evaluation of risk to agree that at least something ought to be done; the possible outcomes include ones that are simply unacceptable.

We never make policy or even personal decisions based on absolute certainty. ....

How we misjudge the risks of oil depletion and climate change
http://www.resourceinsights.blogspot.ca/2012/10/how-we-misju...