Recommendation 8

Emissions reduction policy is built on long-term climate and economic modelling, with large built-in uncertainties. Broadly, governments seeking to map a long-term plan of action can respond to this in one of two main ways:
they can share only the outputs (i.e. the final figure that is reached on a cost or benefit calculation) and not the underlying assumptions which are key inputs for their modelling. Governments could defend this approach by reference to the technical and contingent nature of modelling inputs, and the risk of these becoming a distraction, when the focus should be on overall policy direction and prioritisation and on delivery. They could also compensate by providing more detailed narrative sections about the detail of policy and its delivery;
or they can publish all their main assumptions and modelling processes within or alongside the Plan, making these part of the overall conversation about whether the action plan looks likely to meet its aims, and where the main risks might lie.