Bob TippeeEditorAs efforts to cut emissions of carbon dioxide founder, negotiators at the latest round of United Nations climate change talks are looking to other greenhouse gases.According to news reports from meetings in Cancun, Mexico, some policymakers are considering curbs on emissions of, among other non-CO2 gases, methane. But that route will lead to the same dead-end that stymied the push for CO2 reductions.As proposed sacrifices become clear, people begin demanding convincing answers to an important question: Why?With CO2, answers have been muddled by scary projections increasingly seen as exaggerated and, in Europe, by an inexplicable push to lead the world into ever-increasing ...