In his new book “Climate Justice: What Rich Nations Owe the World — And the Future,” Professor Cass R. Sunstein ’78 argues that wealthy nations, which have benefited the most from industries that cause greenhouse gas emissions, have a responsibility to compensate poor nations as well as future generations.
During a recent book talk at Harvard Law School, Sunstein lasered in on the evolution of the “social cost of carbon,” the measure used by global policymakers to determine the financial cost of emitting one additional ton of carbon dioxide into the atmosphere.
Sunstein, the Robert Walmsley University Professor, recalled working in the Obama White House, heading the Office of Information and Regulatory Affairs when the measure was first adopted in 2009 in response to an executive order.
“The process was extremely nonpolitical, I can vouch for that,” he said. “It was highly technical, by people whose political views I had no idea of.” In a chart during the talk, he described the statistic as “the most important number you’ve never heard of.”
Borrowing a catchphrase from Taylor Swift, he embarked on an “eras tour” of how this cost came to vary in different administrations. Initially, the cost was calculated at $50 per ton, which Sunstein said was a fair ballpark figure at the time. It plummeted to $2 during the first Trump administration, only to jump to around $190 after Joe Biden entered the White House.
Sunstein believes the cost is likely to drop again during Trump’s second term. He said President Donald Trump recently issued an executive order that seems to call for jettisoning the social cost of carbon altogether, putting it in “some sort of purgatory” for the time being.
These large fluctuations, Sunstein said, have a profound effect on climate policy. “The number really matters, in the sense that if the damage done by a ton of carbon emissions is [calculated as] zero or little, then the justification for regulations that reduce climate emissions is small, maybe invisible,” he said. “And the justification for eliminating regulations that reduce climate change emissions is very strong … The differences between President Trump and Presidents Biden and Obama shouldn’t be directionally surprising, given their general views about these topics.”
But how, he asked, was the number able to go down so dramatically during the Trump administration? The answer, he said, was “staggeringly simple.” Previous administrations calculated global climate damage; the Trump administration only considered it domestically.
While the Biden and Obama administrations factored in consequences to other nations, Trump’s was guided by “DSI,” domestic self-interest. “They thought … that what matters when the United States regulates is what happens to American citizens … We focus on our own people, not on other people,” Sunstein said. “That is the great debate.”
The DSI philosophy and use of the domestic number, he said, fails to consider the extent to which all nations are connected. “If there’s harm done, let’s say, to people in Mexico or South Africa, the United States is affected … first because there are Americans living in [those countries], and second because bad things that happen [there] end up harming Americans, either through migration or through interconnected economic relationships.” Another argument made by Presidents Obama and Biden, he said, is that the social cost for any particular country is a challenge to tally accurately.
A return to the global number would make sense both morally and practically, Sunstein said. The “moral cosmopolitan” argument, he said, is that a country causing harm to the citizens of another country is obliged to stop doing so and to give compensation. More practically, he said that “if every country on the planet used the domestic number, every country on the planet would be hurt badly.”
Thus, if China used only the domestic measurement for the cost of its carbon emissions, it would not be factoring the harm it was doing to the rest of the world. And if the U.S. uses the domestic number, that can prompt other nations to do so, and further harm would result.
So, he said, America’s self-interest would be best served by using the global number. “We might say loud and proud … that we use the global number in order to protect the American people, who’d be at risk if the rest of the world’s nations didn’t consider the harm they were doing to the rest of the world from their emissions.”
Turning to “brass tacks,” he said the U.S. has quantifiably contributed the most to greenhouse gas emissions, while China now contributes the most annually. Meanwhile, poorer nations have become the most affected by climate change, notably Pakistan which recently experienced extreme flooding. In that way, he said, nations that contribute the least to climate change are the most vulnerable to it. “This is an asymmetry of the most unwelcome sort.”
Invoking songwriter Bob Dylan, Sunstein noted that richer countries have brought “hard rain” onto poorer ones through climate change, and that some form of corrective justice is morally required, just as it would be if one individual harmed another.
“One nation has benefited from economic activity that’s inflicted serious harm on others,” Sunstein said. “And that gets us enough of the way to a corrective justice argument.”
The actual amount of mitigation needed, he admitted, would be hard to calculate — particularly since rich countries have also aided poor ones through medical and technological innovations. Still, he noted the obligation to devote resources to protecting vulnerable countries, and to providing mitigation in the form of reduced emissions. “How much? Let’s just say, a lot. And then we can haggle over the price.”
The political timing “may not be exactly perfect” for his book, he said, joking that he was considering changing the title to “Tariff Justice” or “Buying Greenland.”
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