Baltimore Sun: Bob Doppelt’s column “Let’s think sustainably” (Commentary, Sept. 9) argues that to tackle global warming, we must shift to “sustainable thinking” and should recognize how our choices about what we consume result in direct and indirect emissions of greenhouse gases. He claims that the climate problem is, at its core, one of vision, not flawed policy. Yet he fails to mention the only policy that could effectively encourage us to think sustainably: a tax on carbon. Under such an …