There is a low-tech way to sequester carbon dioxide: don't dig up so much coal and oil in the first place. Princeton University's Carbon Mitigation Initiative concludes that using the most efficient building technologies for commercial and residential buildings could avert as much carbon dioxide as is produced by 800 one-gigawatt coal power plants. Doubling automotive efficiency -- possible with existing technology -- would achieve the same. Do both and you've canceled out the emissions of 1,600 coal power plants -- more than all the coal plants proposed globally today.

Clearly, even partial deployment would yield enormous benefits. So what's the problem? "The classic reason why efficiency didn't fare well [is that] it took five guys in a corporate boardroom to spend a couple billion bucks to build a power plant that can power 250,000 homes," says Steve Selkowitz, who manages building-efficiency research programs at Lawrence Berkeley National Laboratory in Berkeley, CA. "Getting 250,000 homeowners to each change 10 light bulbs and buy a more efficient refrigerator and air conditioner takes much more effort."