On Friday, the Federal Highway Administration (FHWA) reported that Americans drove 11 billion fewer miles in March 2008 than in March 2007. According to the FHWA, that's the sharpest drop since the agency began keeping records in 1942.

Calculated Risk provides some context:

This is only the third time since 1970 that the year-over-year change in total U.S. miles driven has declined. The previous two times were following the oil shocks of 1973 and 1979 -- and led to the two most severe U.S. recessions since WWII.

But there is some good news: The Department of Transportation also reported that "greenhouse gas emissions fell by an estimated 9 million metric tons for the first quarter of 2008," presumably in part because of all the miles not traveled.

Right-wing think tanks are always complaining that taking meaningful action to address climate change will choke off economic growth. But it could just as easily work the other way around: A collapse in economic growth might choke off global warming.