National Public Radio: There’s an experiment going on in the redwood forests of northern California: people are trying to turn trees into "carbon banks." The idea is to manage forests so they absorb more carbon dioxide from the atmosphere and slow down global warming. Carbon banking will be a hot topic at next month’s big climate conference in Copenhagen, especially if negotiators can’t agree on how to get industrialized countries to lower their own emissions. Carbon banking could be a way to cut those …