On his mock-"conservative news" show, Stephen Colbert once earnestly implored an environmentalist guest who warned about the impact of unrestrained carbon emissions, "Please, tell me, what can I do to cut carbon emissions ... without inconveniencing myself in any way?"

Many businesses feel that way. Their first choice would be for no system, but by now most businesses realize that some sort of regulation is inevitable. Their biggest wish is for a clear signal from regulators about what's required of their companies. Given this reality, their clear second choice among methods to cut greenhouse gases is "cap-and-trade," also known as emissions trading.

Precedent has a lot to do with this. Emissions trading began in the 1990s for sulfur dioxide