Protecting the Ozone Layer in the Face of Uncertainty

It has been predicted by numerous scientists that exhaust pollutants from large fleets of aircraft flying in the stratosphere will lead to diminution of stratospheric ozone leading in turn to increases in ultraviolet radiation reaching the ground and thence to increases in human skin cancer. Each step in the chain, from determining the amount of emissions to determining the net change in skin cancer, is accompanied by significant uncertainties. Acknowledging these uncertainties, what steps may reasonably be taken to avoid undue damage either to the environment or to the aviation industry?