Yesterday, President Bush signed the energy bill, saying it would help deal with climate change. Hours later, his Environmental Protection Agency refused to allow 17 states to set their own vehicle emission standards to help curb global warming. Today when asked how serious he is about fighting greenhouse gases, the President defended the effectiveness of a national, rather than state, environmental policy. California is the leader among states who want to set their own emission standards. Zachary Coile reports from Washington for the San Francisco Chronicle.