Fittingly, Krupp's work has framed the global warming debate. He played a key role in enlisting corporate support for government action. And because of the success of the acid-rain program, a cap-and-trade scheme for greenhouse gases is the basis for proposals in Congress to combat warming. Today, lobbying for a tough greenhouse gas law is a top priority for Environmental Defense. "Don't mistake me for someone who thinks markets will solve problems without the government," Krupp says.