GLOBAL WARMING POTENTIALS - AMBIGUITY OR PRECISION AS AN AID TO POLICY

It is widely assumed that the more certain and precise the scientific knowledge-base for predicting and understanding climate change, the be tter defined and robust will be the policy measures undertaken in resp onse. In this paper we argue to the contrary that in the case of Globa l Warming Potentials (GWPs) ambiguity in their precise meaning is a ma jor reason why they have been developed and continue as scientific pol icy tools [although this is not how they are commonly represented in t he reports of the Intergovernmental Panel on Climate Change (IPCC)]. W e survey and analyse the range of opinion on GWPs with respect to thei r scientific stability and comprehensiveness and argue that the utilit y of GWPs has to be evaluated in terms of their symbolic, interactiona l and heuristic effects as well as with respect to their direct instru mental uses. In addition, we argue that scientific discussion of GWPs commonly incorporates elements of the social and policy contexts of th eir application and provide several examples from detailed discussions at the IPCC. We endeavour to account for the ambiguous identity of GW Ps and draw out several implications from the findings of the paper fo r the construction and use of scientific tools in policy.