Just the day before Kurt Cobb made a similar point in discussing the need for "vigorous preparations" on climate change, even if the worst scenario is only 5% likely:
If you were told that the trans-Atlantic flight you were about to board only crashes 5 percent of the time, would you still board that plane? My guess is that you would change your reservations. Even with a 95 percent chance of surviving the flight, you would find the risk of death too high.
It is akin to the old adage of an ounce of prevention being worth a pound of cure. The cost of preparation for something that might never occur dwarfs the costs (financial, political, social) of dealing with it when it does. It is this straightforward calculation that impels people to buy insurance.
Why would we treat climate change differently?
One difference of note is that this we would be buying this figurative insurance to mitigate something with a much higher likelihood of occurring than just 5%. It's rather more like buying fire insurance after your attic is already ablaze.
Another difference is that, unlike actual insurance, we'd be buying something that produces real benefits even if (in some bizarrely unlikely scenario) somehow climate change never occurs or has no significant effects. Investing in the cleantech economy, reducing fossil fuel use, and promoting sustainability will pay real benefits: creating jobs, improving air quality and human health, and boosting global economic competitiveness.
The airline analogy "shows how sensitive humans are even to low probability events if the outcomes are severe enough." The intelligent choice is to take immediate action. It's simple game theory.