A new report bobbing around the climate policy waters suggests that over the past five years alone, the United States has directly benefited from international climate action to the tune of at least $60 billion — and that number could be as high as $231 billion. What’s more, argues NYU Law’s Institute of Policy Integrity (IPI), is that if countries follow through on their climate pledges, the U.S. stands to benefit by more than $2 trillion over the next 15 years. Imagine the size of the wall ‘Murca could build with 2 trillion greenbacks.

These are words carefully chosen, though. What does it actually mean to directly benefit from climate action?

To punch out dollar figures, the IPI report leverages a metric called the social cost of carbon. The basic idea here is that CO2 emissions are fairly awful for the world as we know it, and pricing emissions per ton in a commensurate fashion should allow policymakers to better conduct cost-benefit analyses surrounding climate action. Right now, a U.S. federal working group pegs the social cost of carbon at around $41 per ton (although this value is the subject of much economic debate).

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Then, the authors argue, the economic benefits of carbon cuts are simply the opposite of their social cost, had they been emitted. By summing up countries’ emissions reductions and multiplying this number by the appropriate social benefit dollar value (which rises over time, since additional emissions are even worse in the future), they calculate the global social benefit of these carbon cuts. The next step is to weight this global value by the proportion of total climate benefits that researchers estimate flow to the U.S. given any reduction in global emissions (the authors use the range 7–23 percent). The resulting figure represents global climate action’s direct benefits to the United States.

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It’s a fickle set of calculations. The Interagency Working Group on the Social Cost of Carbon, for example, which came up with the $41 figure and the 7–23 percent range, described that same range as “approximate, provisional, and highly speculative.” And the social cost of carbon wasn’t really designed to capture benefits. It was designed to quantify the environmental, public health, and economic damage wrought by greenhouse gas emissions. What the report really says, then, is that emissions reductions in other countries are saving the U.S. relative dollars. That CO2 and climate change cost a lot, and with cuts in carbon emissions, they’ll cost the country a bit less. But these are not real dollars appearing in federal coffers.

In other words, there’s no counterfactual here. The report states, for example, that “we can calculate a range of direct benefits that the United States has already gained from Europe’s actions as, at minimum, between $101 million and $662 million just from emissions reductions in the year 2010 alone.” But 2010 is only going to happen once. We have no way of knowing what 2010 would have cost the U.S. without Europe’s climate action.

But the squishy nature of the numbers doesn’t mean the IPI report isn’t an important effort. The social cost of carbon is particularly difficult to quantify, and it’s a good thing that we have some ballpark figures on the table for the U.S. benefits of global carbon cuts. Costs and benefits are already exceptionally arbitrary, and fighting fire with fire could promise additional arguments for U.S. climate action in the first place. “For example,” write the authors, “the Clean Power Plan — EPA’s regulation of the carbon emissions from existing power plants — is estimated to cost as much as $8 billion per year.”

Yet not only do the Clean Power Plan’s air quality co-benefits to U.S. public health (up to $34 billion per year) alone far exceed those costs, and not only do the regulation’s climate benefits (about $20 billion in 2030) also far exceed those costs, but the benefits to the United States from action taken by other countries far exceed the costs of this U.S. climate regulation.

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In the game of cost-benefit analysis, it’s a point worth making.