Timing Regulations to Prevent Stratospheric-Ozone Depletion

Decisions concerning whether to impose regulations to restrict emissions of potential ozone-depleting substances must be made in a context characterized by three important features: (1) estimates of the likely extent of future stratospheric-ozone depletion and its consequences for life on earth are highly uncertain; (2) continuing scientific research can be expected to reduce, but not eliminate, these uncertainties; and (3) the relationship between potential-ozone-depleter production and environmental consequences is characterized by lags on the order of decades or more. Using a simple decision-tree framework, this research addresses the key question of whether it is desirable to impose emission-limiting regulations now, or to wait five to ten years to develop improved scientific understanding before deciding whether to regulate. Under a wide range of assumptions, beginning regulations immediately is cost-effective if the probability that regulations will eventually be required exceeds about 0.3 to 0.5. The research was presented at the September 1986 United Nations Environment Programme Workshop on the Control of Chlorofluorocarbons.