The policy question of what response to take to current and developing understanding of the possibility that emissions of certain anthropogenic chemicals may deplete stratospheric ozone and promote a global warming, thereby increasing ultraviolet radiation at the earth’s surface, modifying climate, and potentially producing a host of adverse effects, can usefully be structured as a stochastic dynamic program with endogenous learning. This structure clarifies the relationships between appropriate actions and understanding of the relationships between policy and possible outcomes. However, a structure that incorporates all of the prominent features of the problem is mathematically intractable. To provide useful policy guidance, a substantially simplified model like the one presented may be valuable.