Maybe I’m naïve, but I’m feeling optimistic about the climate talks starting in Copenhagen on Monday. President Obama now plans to address the conference on its last day, which suggests that the White House expects real progress. It’s also encouraging to see developing countries  including China, the world’s largest emitter of carbon dioxide  agreeing, at least in principle, that they need to be part of the solution.

Of course, if things go well in Copenhagen, the usual suspects will go wild. We’ll hear cries that the whole notion of global warming is a hoax perpetrated by a vast scientific conspiracy, as demonstrated by stolen e-mail messages that show  well, actually all they show is that scientists are human, but never mind. We’ll also, however, hear cries that climate-change policies will destroy jobs and growth.

The truth, however, is that cutting greenhouse gas emissions is affordable as well as essential. Serious studies say that we can achieve sharp reductions in emissions with only a small impact on the economy’s growth. And the depressed economy is no reason to wait  on the contrary, an agreement in Copenhagen would probably help the economy recover.

Why should you believe that cutting emissions is affordable? First, because financial incentives work.