Klaus Lackner a physicist at Columbia  University,has a solution to global warming:Vacuum carbon dioxide out of the air. Klaus Lackner ,suggested placing enough carbon filters around the planet could reel the world's atmosphere back toward the 18th century like a climatic machine. He 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. The dream has pushed scientists to work on massive schemes to reengineer the planet. The filters would have to be powered by new nuclear plants,dams,solar farms or other clean-energy sources to avoid adding more pollution to the atmosphere.