Back in June, we wrote about Cash for Clunkers, noting that it was very expensive for the small amounts of CO2 it reduced.

Now, our conclusions are being cited and echoed by many others.

Slate Magazine, picking up on our analysis, wrote this:

Was spending $1 billion a particularly cost-effective way to achieve those CO₂ reductions? Probably not. Assuming the above calculations are correct and that each consumer keeps his or her car for 10 years, then the total savings should be a little less than 5.7 million tons of carbon dioxide. That means each ton of carbon dioxide would be worth about $175.53 to the U.S. government. As the Washington Policy Center pointed out on its blog in June, a ton of CO₂ currently goes for about $17.50 on the European Climate Exchange.

AP environmental writer Seth Borenstein echoed that sentiment, quoting an MIT expert who comes up with numbers similar to ours.

Paying up to $4,500 per clunker means the government is spending more than $160 for every ton of carbon dioxide removed over 10 years, said MIT's Jacoby, co-author of the book "Transportation in a Climate-Constrained World." That's five to 10 times more than the estimated per-ton cost of carbon dioxide for power plants in the cap-and-trade system passed earlier this year by the House.

We are frequently bombarded with claims that one policy or another will make significant reductions in CO2 emissions. Too often, however, the estimates of cost and effectiveness are done only after the policy is being implemented. It shouldn't be surprising that we are often disappointed about the results of those policies.