John Allen Paulos in his brilliant Who’s Counting column at ABC News:
…Robert Louis Stevenson’s story “The Imp in the Bottle” provides a fictional illustration of the psychology behind one sort of dismissal of global warming. It is the story of a genie in a bottle who will satisfy your every wish for love, money and power. You can buy this amazing bottle for any amount that you care to offer. The only constraint is that when you are finished with the bottle, you must sell it for a price strictly less than that you paid for it. If you don’t sell it to someone for a lower price, you will lose everything and suffer everlasting torment in hell. What would you pay for such a bottle?
Certainly, you won’t pay 1 cent for it because then you won’t be able to sell it for a lower price. You won’t pay 2 cents for it either because no one will buy it from you for 1 cent for the same reason. (Everyone knows that it must be sold for a price less than the price at which it is bought.) Neither will you pay 3 cents for it; the person to whom you would have to sell it for 2 cents would object to buying it at that price since he wouldn’t be able to sell for 1 cent.
A similar argument applies to a price of 4 cents, 5 cents, 6 cents and so on. Mathematical induction can be used to formalize this argument, which proves conclusively that you shouldn’t buy this magic bottle for any amount of money. Yet you would almost certainly buy it for $1,000. I know I would. At what point does the argument against buying the bottle become practically convincing?
As the above thought experiment illustrates, the consequences of our decisions need not occur in the distant future for us to discount them. They can occur far away or after so many steps as to seem distant.