From “Weighing the Future,” an Economist piece about how the dismal science can frame the argument for sacrificing now to combat climate change when the worst effects might not be felt for centuries:

“But all of these changes will be felt most severely decades or centuries down the road: after our children, and our children’s children, are gone.

That is a nasty complication for economists trying to figure out the most appropriate way to respond to climate change. Some economists, like Martin Weitzman, reckon that significant investment may be justified now as a form of insurance. There is a risk that climate change will happen faster or be more costly than we anticipate, possibly threatening humanity’s very existence. Whether or not it makes sense to pay to cut emissions in order to enjoy the benefits of slower warming, it is worth taking action now in order to reduce the odds of a civilisation-ending outcome.

Though that argument makes quite a lot of sense, it does leave some economists unsatisfied. Surely the costs of warming are high enough that it’s worth cutting emissions to stop it, whether or not it threatens our very existence, right?

It seems like that ought to be the case. But to suss that out, we have to make an assumption about discount rates—that is, how much we, today, should value benefits received well down the line—in order to compare costs today to benefits tomorrow.

If one believes that humanity should take drastic action now even though it might slow economic growth, one has to assume that future costs will be very, very big or that people living today place significant value on benefits realised 50 or 100 or 500 years down the line. And that strikes many dismal scientists as implausible. It is easy enough to imagine that people living today care about benefits that might accrue to them in their old age, or that of their children or grandchildren. But look much beyond a century and the beneficiaries become too distant to count much in our mental calculus.”