Gary Yohe with the “burning embers” diagram

written for the Yale Climate Media Forum

Economist Gary Yohe is no newcomer to the costs and benefits of combating climate change.

For decades, the Wesleyan University mathematician-turned-economist has been calculating the price of climate change—what it would cost the economy if countries act, or don’t, to reduce greenhouse gas emissions. As a senior member of the Third and Fourth Assessments of the Intergovernmental Panel on Climate Change, Yohe shares with his IPCC colleagues a fair claim on the 2007 Nobel Peace Prize, and he has emerged from his academic milieu into a more public one.

Now he finds himself translating his expertise into layman’s language for policy makers and ordinary citizens. Three times in recent years he testified to congressional committees on how he believes climate change and our response to it will affect the world economy in dramatic ways.

Yohe is in a strong position also to evaluate how the media have handled – both stimulated and responded to – increased public interest in climate science with the release of the IPCC’s Fourth Assessment Report two years ago. With a clear consensus in the scientific community that humans have accelerated rising world temperatures, Yohe sees evidence that reporters better understand the difference between covering politics and opinions and covering scientific consensus.

“In a political story, when it’s 55 to 45 or 51 to 49, it makes sense to cover both sides of the argument,” Yohe said in a recent interview in his campus office. “But when it’s a scientific argument, when there’s 99 on one side and one on the other, it makes no sense to cover both sides. They are doing better.”

Yohe in particular credits The New York Times’s Andrew C. Revkin for helping spread increased understanding of the strength of the scientific consensus in coverage and helping others in the media understand that consensus.

Yohe says that good articles about climate change should reflect the scientific consensus that the climate is warming and that humans have accelerated this warming. Then they can go from there to say that, notwithstanding these strong conclusions, scientists are still testing various theories, such as those that link hurricanes and severe weather to climate change.

Accuracy Still “Spotty”

While acknowledging improvements in climate science coverage on the part of many news organizations and reporters, Yohe nonetheless is bothered by continued sloppiness in some media reports.

Overall, “the level of accuracy is spotty,” he says. Reporters’ tendency to seek concrete examples of climate change has led to problems in some cases. An oft-repeated example, for instance, involves media pointing to melting glaciers on the iconic Kilimanjaro as a sign of global climate change. The mountain figured prominently in the Al Gore movie, “An Inconvenient Truth,” and the media might not be entirely at fault for focusing on the snows made famous by Ernest Hemingway, since the IPCC Fourth Assessment Report itself dealt with the issue at length.

But scientists more recently have learned much more about Kilimanjaro’s glaciers, and Yohe points out that some in the media have been slow to pick up on that new knowledge. He points to research published by respected scientists Phillip W. Mote and Georg Kaser, who wrote in the American Scientist in Spring 2007 that the story on Kilimanjaro snow-melt is more complicated. The rapid melting in fact is primarily the result of sublimation, or evaporation from solid to gas, itself brought about by a range of factors (”The disappearing ice cap of the ’shining mountain,’ which gets a starring role in the movie,” Mote and Kaser write, “is not an appropriate poster child for global climate change.”)

Prefers Carbon Taxes to Cap and Trade

The important message Yohe repeats these days is that he favors a carbon tax on greenhouse gas emissions rather than a cap-and-trade system, as included in legislation moving through the House of Representatives. Over the years he has written many academic articles exploring that rationale. (For a partial list of his scores of related writings, see the end of this article.)

Yohe has taught economics at Wesleyan since 1977, and he is currently the Woodhouse/Sysco professor of economics there. This academic year he also was visiting professor of economics at the Yale School of Forestry & Environmental Studies. He studied mathematics as an undergraduate at the University of Pennsylvania, and graduated Phi Beta Kappa in 1970.

From Math to Economics to Carbon Emissions and IPCC

After earning a master’s degree in mathematics at the State University of New York at Stony Brook, he decided that he wanted to change focus. He claims that he realized that he wasn’t smart enough: “I figured out that the people in Ph.D. programs were really smart. I’d end up driving a taxicab.” So he altered his path and went to Yale University, where he earned his doctorate in economics in 1975.

At Yale, he became interested in price and quantity controls – two areas germane to the debate between cap-and-trade and a carbon tax.

By the early 1990s, his mentor, William Nordhaus, asked him to collaborate on a project for the National Academy of Sciences involving carbon emissions. That work led to more work on climate change and some reviewing for the IPCC Second Assessment in 1995. He was lead author for four chapters in the IPCC Third Assessment Report in 2001, and convening lead author and a member of the synthesis report for the IPCC 2007 Fourth Assessment.

As a mathematician who turned early to economics, Yohe has an interest in climate policy that has little to do with politics. It has to do instead with linking temperatures to risk, to comparing costs of reducing greenhouse gases now or in a few more decades. But with the political discourse having entered the world of climate modeling, Yohe is comfortable facing up to the task of explaining the models to opinion leaders and decision makers who struggle to understand climate statistics and how to use them to anticipate outcomes.

On the wall of his office hangs a diagram well-known to those in the climate change field: “the burning embers diagram,” showing that the higher the global average temperature rises in the future, the greater the risk of disruption to, essentially, all aspects of life. Having first appeared in the IPCC Third Assessment Report in 2001, the diagram has since been updated to show even more alarming risks ahead – but this visual was not part of the most recent IPCC report. (To read Yohe’s explanation of the diagram and to view it, see his testimony before the Senate Foreign Relations Committee in 2006.)

Tell Truth or Set Yourself Up for “Looking Silly”

A soft-spoken professor in command of his topics, Yohe is not one to set out to ingratiate himself with anyone. He once disagreed with then-Senator Joe Biden at an informal meeting after he had testified on climate risks before the Senate Foreign Relations Committee. He doesn’t recall the exact point of contention, but he does remember well that his daughter Courtney, working as a lobbyist at the time, sat in the meeting and kicked her father’s chair when he stood up to Biden.

This sort of thing had come up before. In October 2007 he told a subcommittee of the Senate Banking Committee that even though some groups were pushing to calculate the material risk of climate change, he had to advise them that the risk should probably be calculated at zero for the time being, since such a calculation was so difficult, perhaps impossible, to do without more information. He says he could not provide a reasonable answer in the absence of a lot more information not then available to him, including how proceeds from a carbon tax would be used.

“The senators didn’t seem to be shocked,” he said. “It strikes me—it always has in this game—you really have to tell the truth. If you don’t, then you just set yourself up for looking silly. You absolutely have to give it to them straight. And if you don’t know, it strikes me that you have to say that you don’t know. Or, ‘I’ll get back to you.’”

For all his confidence in both his knowledge and his drive to know more before commenting on an issue, Yohe says he doesn’t take himself too seriously. He likes to golf, but he says his game has gotten rusty over the past several years. He still plays nine holes once a week in Portland, Connecticut. His best score for 18 holes? “Sixty-two. Last century,” he says. “These days, I try to break 80.”

Perhaps his higher golf score reflects his having spent much of his free time traveling the world for meetings and lectures. He takes no pay for his work for the IPCC, which does reimburse him for his travel expenses.

Is he hopeful about the future? He says he is, and that’s why he keeps doing what he does to better understand, and help others better understand, the costs of acting, or not acting, on climate change.

His professional life has expanded beyond teaching to perfecting and analyzing models that conclude, to put it brutally simply, that it is becoming more expensive not to reduce greenhouse gas emissions from power plants and cars than it is to continue examining the issue.

The costs of not acting show up years from now in damage from a dramatically altered climate, he says. That’s a cost he seems unwilling to pass on to future generations.


About This Article

Gary Yohe’s office at Wesleyan is a 20-minute drive for me. He was very easy to talk to and did not think any question was too elementary. This first was posted to the Yale Forum on Climate Change and the Media on June 25, 2009. See…

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