WorldChanging Allies Chris Phoenix and Mike Treder of the Center for Responsible Nanotechnology have written a terrific (and brief) essay on the application of the Precautionary Principle to nanotechnology in particular, and to emerging scientific and technological concerns more broadly. We've talked about the Precautionary Principle before (follow the link for the standard definition, if you're not familiar with the term); it's a useful method of thinking about how to respond both to new technologies and to new scientific understandings of global change. There are two broad forms of the Principle, characterized by Phoenix and Treder as the "strict" version and the "active" version. The strict form holds that research and development which can be shown to have possible harmful results should be stopped, period. There actually aren't too many people advocating this position, but they do exist. The active Precautionary Principle "calls for choosing less risky alternatives when they are available, and for taking responsibility for potential risks." Rather than the traditional risk assessment method of asking "how much harm is acceptable?" the active form of the Precautionary Principle asks "how much harm is avoidable?"
Although the Precautionary Principle is generally applied to implementations of new technologies, the active form is a useful way of thinking about how we respond to global warming induced climate disruption. As the 1992 Rio Declaration on the Environment and Development put it,
Principle 15: In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.