Klaus Lackner, a Columbia University physicist, has proposed a new solution to global warming: massive carbon dioxide vacuums. The Los Angeles Times reported last month that "placing enough carbon filters around the planet could reel the world's atmosphere back toward the 18th century, like a climatic time machine." The only major obstacle is cost. Lackner "estimates that sucking up the current stream of emissions would require about 67 million boxcar-sized filters at a cost of trillions of dollars a year." Though some researchers claim that there is enough room in rock formations below ground to trap filtered carbon "forever," the storage process isn't cheap. "Experts estimate that it would cost up to $200 a ton to filter and store carbon dioxide from the air. That means the yearly vacuuming bill could reach $5.6 trillion." But carbon vacuuming may prove more feasible than some other large-scale proposals floating around. "One idea is to block sunlight, either by constructing artificial volcanoes to blast sulfur particles into the atmosphere or by launching millions of tiny satellites into space and arranging them into a giant mirror."

http://www.latimes.com/news/science/la-sci-carbon29apr29,0,2175412.story?page=1