Capital in the Twenty-First Century

by Thomas Piketty

William Nordhaus, an American, argued that one ought to choose a discount rate closer to the average return on capital (4–4.5 percent a year), a choice that makes future disasters seem much less worrisome. In other words, even if everyone agrees about the cost of future disasters (despite the obvious uncertainties), they can reach different conclusions. For Stern, the loss of global well-being is so great that it justifies spending at least 5 points of global GDP a year right now to attempt to mitigate climate change in the future. For Nordhaus, such a large expenditure would be entirely unreasonable, because future generations will be richer and more productive than we are. They will find a way to cope, even if it means consuming less, which will in any case be less costly from the standpoint of universal well-being than making the kind of effort Stern envisions. So in the end, all of these expert calculations come down to a stark difference of opinion.