Every degree of warming, it’s been estimated, costs a temperate country like the United States about one percentage point of GDP, and according to one recent paper, at 1.5 degrees the world would be $20 trillion richer than at 2 degrees. Turn the dial up another degree or two, and the costs balloon—the compound interest of environmental catastrophe. 3.7 degrees of warming would produce $551 trillion in damages, according to at least one estimate—almost double the amount of wealth that exists in the world today. Multiply four degrees by that 1 percent of GDP and you have almost entirely wiped
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