ON JULY 12, the Larsen C ice shelf in Antarctica disgorged a chunk of ice the size of Delaware, a small state on America’s east coast. America’s government seems unfazed by the possibility that such shifts might one day threaten Delaware itself. Its climate defiance grows not only from the power of its fossil-fuel industry and the scepticism of the Republican party, but also from a sense of insulation from the costs of global warming. This confidence is misplaced. New research indicates not only that climate change will impose heavy costs on the American economy, but also that it will exacerbate inequality.

Calculating the economic effects of climate change is no simple matter. It means working out how a given increase in global temperature affects local weather conditions; how local weather affects things like mortality and crop yields; how those changes add to or subtract from regional GDP; and how thousands of local-level changes in GDP add up nationally or globally. No...Continue reading