Economists were able to formulate and recommend policy approaches for reducing emissions of greenhouse gases (mitigation) by drawing on an existing body of economic theory related to externalities. However, no comparably straightforward approach has yet emerged in the adaptation literature, possibly due to the diffuse nature of climatic effects that may occur in very diverse geographical locations. By acknowledging that the hallmark of future climate change effects is uncertainty, rather than readily identifiable and deterministic outcomes, it is possible to formulate coherent policy approaches. Recognising that there are differing degrees of uncertainty is a key aspect to making policy formulation more realistic.