- Authors: Mark Budolfson, Michael Geruso, Kevin Kuruc, Dean Spears, and Sangita Vyas
- R&R at JPE Macro
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We test the widely shared view that an important benefit of the ongoing, global decline in fertility and population growth will be reductions in long-run temperatures. We assess climate outcomes and average per capita incomes under a baseline scenario of depopulation against a counterfactual in which the world population stabilizes at a level higher than today’s. Although these paths differ by billions of people in 2200, we find that the implied temperatures differ by less than one tenth of a degree C. Timing drives this result. Fertility shifts take generations to meaningfully change population size, by which time per capita emissions are projected to have significantly declined, even under pessimistic policy assumptions. This makes the additional warming from any plausibly sized fertility changes small relative to other well-studied effects of population growth, including non-rival innovation. Moreover, once the possibility of net-negative emissions is accounted for, even the sign of the population-temperature link becomes ambiguous.
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