The Montreal Protocol on Substances that Deplete the Ozone Layer is often recognized as a potential model for climate change. Like climate change, ozone depletion is a global environmental threat. In this case, emissions of human-produced chlorofluorocarbons (CFCs) are destroying the ozone layer that protects the Earth’s surface from harmful solar ultraviolet (UV) light. Like the greenhouse gas (GHG) emissions that cause climate change, these emissions come from a variety of industrial processes taking place in both developed and developing countries, with the bulk of such emissions originating historically from the industrialized world. Also as in the case of climate change, scientific research discovered an unintended consequence of modern industrial activities that is largely invisible to the eye yet has potentially very serious global consequences. Furthermore, the early years of ozone layer research were filled with scientific uncertainties. For example, in 1974, based on laboratory research, chemists Mario Molina and Sherwood Rowland first hypothesized that CFCs were stable enough to rise to the stratosphere, where they would break down the Earth’s protective ozone layer (Molina and Rowland, 1974). Their research was roundly criticized by a number of companies that produced or relied upon CFCs. Nonetheless, the news media reported their hypothesis and identified common household products (such as aerosol spray cans) as one of the sources of CFCs. The public quickly responded, with many choosing to avoid CFC-based products. It was not until 1985 that British Antarctic Survey scientists finally discovered the formation of an ozone “hole” in the stratosphere over Antarctica (Farman et al., 1985). That same year, the Vienna Convention for the Protection of the Ozone Layer was negotiated and signed by many of the world’s largest emitters; this was quickly followed by the Montreal Protocol, which entered into force in 1989.
Technological innovation and market position played critical roles in the policy-making process, because the same companies that had produced CFCs invented more benign substitutes. The structure of the Vienna Convention was also important, as it included a periodic review of the evolving science, a structure by which the treaty could be revised and updated over time, and a special fund to assist developing countries in complying with the treaty. Over the years, as the science has progressed, the treaty has been progressively tightened to achieve a further and faster phase-out of ozone-destroying compounds. As a result, the Montreal Protocol has been hailed internationally as one of the most successful international agreements ever (DeSombre, 2000).
While there are some similarities between the problems of climate change and ozone depletion, there are also some very important differences (Bodansky, 2001; Grundig, 2006). For example, the problematic substances (CFCs) for ozone were produced by