Does Amazon know enough about its supply chain, this fellow asked, to assign a value to the atmospheric carbon attributable to the manufacturing and shipping of its products? Bezos thought that the answer was no, but he was clearly intrigued by the question. So am I.

Consider global warming. We are finally emerging from a long phase of denial and moving into the next phase: ineffectual hand-wringing. In a top news story I read today, for example, United Nations Secretary General Kofi Annan decries the "frightening lack of leadership" on this issue. Perhaps the UN will issue a follow-on report condemning that lack of leadership in the strongest possible terms. Do you think that'll move the needle? Me neither.

Imagine, though, a future version of Amazon.com where the price for each product is reported in two different ways: as dollars (P1), and also as carbon-adjusted dollars (P2). Now consider a pair of competing products, A and B, under two different scenarios.

In one scenario, A's P2 is lower than B's, but A's P1 is higher than B's. Some people will be willing to pay the higher P1 (more dollars) to reward A's lower P2 (less environmental impact), but most won't.

In the other scenario, however, A's P2 is still lower than B's, but its P1 is about the same. In other words, there's no penalty to the buyer for rewarding A's lower environmental impact. If the P2 data is available, it's a rational choice.