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But while those are huge numbers by any measure (world GDP is around $100 trillion), they aren’t big enough to motivate most leaders to justify mitigation, which will also cost a whole lot of money.

To put it in terms the authors use, the recently enacted Inflation Reduction Act will cost Americans roughly $80 per ton of carbon emissions avoided, and while each ton not pumped into the atmosphere would save the world $200 as a whole, it would only save Americans about $40 of that $200, making it feel to some altruistic but not self-evident in purely economic terms.

In their new paper, economists Adrien Bilal of Harvard and Diego Känzig of Northwestern take a fresh look at the data

They show that the social cost of carbon is likely far bigger — six times bigger — than previously estimated: losses of more than $1,000 per ton, or around 12 percent of world GDP per degree of warming.

— roughly equivalent to the economic drag on big economies if they were permanently at war.

Suddenly, that $80 Americans are spending on reducing one ton of carbon emissions is netting them $200 or so in U.S. economic activity.

Bilal and Känzig argue that it’s very much worth it for countries of means to spend the money now to avoid much greater costs down the line

the potential losses are so vast it makes sense for these countries to go ahead and act on their own to avoid climate change losses, even if other nations do nothing.

What’s different about your methodology and how did it lead you to the numbers you've come up with?

Adrien Bilal: So virtually all of the previous work that's been done on the subject has relied on comparisons of different countries that heat up or cool down at different points in time. The U.K. gets a little hotter in one year, and then Germany stays cool. And then you look at how GDP in the U.K. evolves following that change in temperature.

that generally gives you numbers in the vicinity of $150 per ton of carbon emitted and a 2 percent decline in GDP per degree Celsius in warming

we think that is quite different from what climate change is actually doing to the world. It's not only that the U.K. is going to heat up a little more than Germany, but the whole world is heating up because of climate change. And, in particular, oceans are also heating up. And when the whole planet warms, that has potentially really different implications for the climate system, increased frequency of extreme weather events that then have big local impacts. 

that's actually what geoscientists have been telling us for a long time, but it simply hadn't percolated into economics. And so we took that perspective very seriously and thought, "Well, what happens when we basically compare years where the world is very hot to years where the world is cooler?" And that gives you a much larger effect of climate change on the economy.