I hate to pick on Jay Leno, but he really makes it too easy. While Leno is a famous gearhead, he seems to share the same basic misunderstanding as many environmentalists who paint the internal combustion engine as the scourge of the planet. Specifically, he seems to think that if a car is powered by something other than gas, it magically becomes non-polluting:

LENO: it's pretty neat. and this week, we drove -- today, I drove the ford escape hybrid. This is what they call a plug-in hybrid. Now, this is not something on the market yet. It's still a little bit experimental. It's a hybrid car, but you plug it in at home and you get 40 miles free, essentially.

EUBANKS: Whoa.

LENO: So, after about 40 miles, the gas engine will kick in. You can charge up the battery if you drive it again. But my commute is like, 18, 19 miles. So, I drive in, plug it in here, drive home. I use no fuel at all...

If Ford really had developed a car that can travel 18 or 19 miles using no fuel, the company would undoubtedly be doing a lot better. The reality is that Leno is eschewing gasoline in favor of a combination of coal, natural gas, and nuclear to power his car. (That's assuming he lives in the City of Los Angeles and gets his electricity from Los Angeles Water and Power). I don't know how old the Los Angeles coal-fired plants are, but the Sierra Club warns that coal plants are a significant global warming threat.

This is just a reminder that when it comes to policy responses to global warming, you're rarely going to get the unvarnished truth. The lawmakers that point to alternative fuels and CAFE standards rarely talk about the cost to taxpayers and car owners. The Leno example is a reminder that for all the excitement over electric cars, there's no such thing as a free lunch -- no matter who tries to tell you there is.