Comment

Integrated assessment models are being used to support R&D portfolio decisions, in order to provide a more systems view on the impact of progress for individual technologies. While the model-supported assessment provides a more structured framework for analysis, it should not hide that there are large uncertainties. This paper shows that results are dependent on the model, the ambition of climate policy and other technology assumptions. It is important in R&D investment advice to realize these uncertainties, and assess the robustness of results against results of other models and studies.