Nathaniel Keohane ’93, a senior vice president at the Environmental Defense Fund, where he leads the climate program, visited Yale on Thursday to discuss climate change and what can be done to stop it. Keohane, who has previously served as a special assistant to former President Barack Obama and as a professor at the Yale School of Management, spoke for an hour at 77 Prospect St. Yale’s Program in Ethics, Politics and Economics organized the talk, which approximately 40 people attended.

“The world is warming, we’re responsible and if we don’t do anything about it, the impacts are really significant. So, what are we going to do about it?” Keohane said to the audience.

Keohane began his talk with a brief data presentation, using graphs displaying the usual markers of climate change, from rising carbon dioxide levels to rising temperatures. His conclusion: Many recent and significant climate-related changes can only be explained by taking into account human influence.

Keohane said scientists are not certain how much temperatures will rise and can only estimate the probabilities — sort of like a weighted roulette wheel. While making that point, he spun a digital roulette wheel on the projector screen with predicted temperature increases, to the mild amusement of the audience.

Around halfway through the talk, Keohane shifted from identifying problems to proposing solutions.

The latter part of the talk focused on what methods for convincing people and organizations to lower their carbon output. In short, he said, to get people to use cleaner energy, they need a financial incentive to do so. On average, each American’s emissions cost society $800. Because no one person pays the cost, though, it can be hard for people to understand their impact, Keohane said.

During his time at Yale, Keohane worked with professor of economics Robert Mendelsohn. Mendelsohn agreed with Keohane’s use of an economics-oriented approach to studying climate change, saying that he agreed that smart policy can make many climate programs more efficient. According to Mendelsohn, who teaches numerous courses on environmental economics, the talk is great for students because it shows them how the things they learn about in class can be put into action.

“You hear all this work that’s academic, but it takes more than that to make the world go around,” Mendelsohn said. “You need someone with ideas who’s going to take those ideas to Washington and actually see if you can form policy around them, and that’s what he has done with his career.”

Mendelsohn did not fully agree with some of Keohane’s more radical claims, however, such as his prediction of potential temperature increases as great as 7 to 8 degrees by the end of the century.

Carrie Heilbrun ’19 attended the talk in part because she plans to work at the Environmental Defense Fund over the summer and wanted to hear Keohane’s perspective on current environmental issues. Heilbrun said she was particularly interested in Keohane’s skillful management of political struggles over carbon taxes and cap-and-trade programs. While Keohane talked at length about politics, Heilbrun said she was glad the discussion covered more substantive matters as well.

“It’s also nice to hear that there’s a lot of optimism at EDF about the potential for technological innovation as a solution,” she said.

Keohane’s talk was part of The Robert H. Litowitz Lectures, which focus on the ethics underpinning big policy questions, according to Charlotte Hulme GRD ’21, one of the organizers of the lecture. As both an academic and a practitioner, Keohane was an ideal candidate for the series, she continued. While some might have been surprised by the talk’s focus on economics, Hulme said, she agrees that it is a valuable approach to studying solutions to climate change.

“You’ve got hardcore environmentalists, and people who are skeptical about how to tackle such a huge political problem,” she said. “By coming at it from an economics incentives approach, you might be able to maybe draw in some of the skeptics and give the environmentalists something different to talk about.”

According to the National Aeronautics and Space Administration, global sea levels are projected to rise another one to four feet by the year 2100.

Maya Chandra | maya.chandra@yale.edu