differentiating among the set of scenarios. During the question-and-comments period, David Montgomery from Charles River Associates noted that a conclusion to be drawn from some of his work is that it is almost always the existence of institutions that allows societies to sustain technology progress and income growth over time. However, the process described by Richard Moss, starting from an RCP, considerably narrows the possibilities of what might actually be explicitly explored with regard to institutions. Moss responded by noting that one of the advantages of starting with an RCP is to say that we have an RCP, but this does not mean that we have to have a single story line that produces a single RCP. Thus, to address an interest in a particular issue, for example institutions and governance, there is no reason to avoid developing a scenario or a story line that focuses on that interest. William Nordhaus commented that he found the RCP approach foreign in that the scenarios then seemed to be organized around variables endogenous to the socioeconomic models. Nordhaus stated that he thought the natural place to start was with baselines, using as inputs some given policies rather than intermediate variables such as RCPs. Moss responded by saying that it is important to think about the issue from the point of view of what the climate modeling community is interested in: the reason for not starting with the story lines is that a great deal of effort had to be expended upfront to get to what the climate people were interested in, and, from the climate-modeling perspective, it did not seem necessary to actually predetermine what those story lines were in order to get to a particular climate future.