William D. Nordhaus, an economics professor at Yale, headed a panel discussion at Harvard on Wednesday and proposed a club model to combat climate change that would require countries to pay a fixed amount for their carbon emissions and penalize non-participants through trade sanctions.

The panel, held in a packed Science Center lecture hall and moderated by Kennedy School of Government professor Sheila S. Jasanoff ’64, was co-sponsored by the Harvard University Center for the Environment, the School of Engineering and Applied Sciences, and the Graduate School of Design. The talk was part of a lecture series on science and democracy organized by the Kennedy School’s Program on Science, Technology, and Society.

Nordhaus said his proposal relies on the idea that countries will be more apt to reduce their carbon emissions under a “club model.” He suggested an international treaty in which countries “move into agreements that they want to be in, not ones they are forced to be in.” These agreements are effective, Nordhaus argued, because nations are voluntarily joining them for the benefit of global public goods.

After Nordhaus introduced his club model, three other panelists joined him on stage to weigh in on his proposal. The panelists included Kennedy School professor Richard Zeckhauser, Physics professor David Keith, and Michael Grubb, a professor from the Institute for Sustainable Resources at University College London.

While Grubb and Keith supported Nordhaus’s proposal, Zeckhauser presented some issues he had with the club model. He cited “not so nice” countries that could easily retaliate against trade sanctions as one problem and said policies like tariffs tend to get out of hand.

He added that major economic players such as the U.S. have a larger role to play in combating climate change, something not accounted for in the club model.

“The United States foot dragged on climate policy… by economic precincts we should have been a big contributor, not a reluctant contributor. I would propose that what we should do is recognize at the outset that the United States is going to have to do more,” Zeckhauser said.

Several audience members said they found the discussion interesting.

Marta Marello, a researcher on energy efficiency at Boston University, said the talk was thought-provoking because it discussed climate change from an economic standpoint, but doubted the viability of some of the ideas proposed.

“There were some great ideas, but they’re probably not going to happen. Especially with countries like the U.S., who’ve dragged their feet for so long,” Marello said. “Why would they jump onto something now? Great in theory, but in practice, how is this going to happen?”