Back in June when I wrote about the upcoming Cash for Clunkers program, few observers actually thought many people would take advantage of it. Surprisingly, then, as you’ve probably heard on the news, it was so wildly successful that it used up its entire $1 billion allotment in a single week!

Great. But what about the environment? The program was sold in part on its carbon-cutting benefits. Giving the owners of gas guzzlers vouchers to buy more fuel efficient cars was supposed to go a long way to improving the fuel efficiency of automobiles on U.S. roads.

So what happened in practice? Here’s a roundup of a few conclusions:

• A CBSNews.com reporter calculated ^[1] that, if the world’s total carbon emissions were represented by the driving distance between San Francisco and New York, the amount of emissions reduced by Cash for Clunkers was equal to the distance between CBSNews.com’s San Francisco office and the nearest subway stop.
• Put another way, the Associated Press calculated ^[2] that the amount of carbon savings from Cash for Clunkers was the equivalent of shutting down power in the entire United States for… one hour. Or, as the Wall Street Journal’s Environmental Capital blog ^[3] put it, “that’s a $1 billion lunch break.”
• The extra $2 billion that Congress approved last week to extend the program came out of ^[4] the Department of Energy’s $6 billion renewable energy loan guarantee program that was part of the stimulus package. That means that the Clunkers program now gets one third of the money that could have supported clean energy start-ups developing new smart grid, wind, and solar technologies.
• The only good news is that among the top new cars that were bought with Cash for Clunkers vouchers were ^[5] models that were much more energy efficient than the program required, like Toyota Priuses and Honda Civics.