Salt Lake Tribune: These should be hopeful times for environmentalists. Junk science no longer rules in Washington. President Barack Obama has spoken forcefully about the need to take action on climate change; the people I talk to are increasingly optimistic that Congress will soon establish a cap-and-trade system that limits emissions of greenhouse gases, with the limits growing steadily tighter over time. And once America acts we can expect much of the world to follow our lead. But that still leaves …