Overall, the paper finds that climate change will cost the United States 1.2 percent of its GDP for every additional degree Celsius of warming, though that figure is somewhat uncertain. If global temperatures rise by four degrees Celsius by 2100—which is very roughly where the current terms of the Paris Agreement would put the planet—U.S. GDP could shrink anywhere between 1.6 and 5.6 percent.
Across the country’s southern half—and especially in states that border the Gulf of Mexico—climate change could impose the equivalent of a 20-percent tax on county-level income, according to the study. Harvests will dwindle, summer energy costs will soar, rising seas will erase real-estate holdings, and heatwaves will set off epidemics of cardiac and pulmonary disease.
The loss of human life dwarfs all the other economic costs of climate change. Almost every county between El Paso, Texas, and Charlotte, North Carolina, could see their mortality rate rise by more than 20 people out of every 100,000. By comparison, car accidents killed about 11 Americans out of every 100,000 in 2015.
But in the South and Southwest, other damages stack up. Some counties in eastern Texas could see agricultural yields fall by more than 50 percent. West Texas and Arizona may see energy costs rise by 20 percent.