In this article, the concept of scenarios is introduced and illustrated with the example of global and regional climate change scenarios. Scenarios are descriptions of possible futures -of different plausible futures. Scenarios are not predictions but "storyboards", a series of alternative visions of futures, which are possible, plausible, internally consistent but not necessarily probable (e.g., Schwartz, 1991; see also Tol, 2007b). The purpose of scenarios is to confront stakeholders and

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... ymakers with possible future conditions so that they can analyze the availability and usefulness of options to confront the unknown future. Scenarios allow implementing measures now to avoid unwanted futures; they also may be used to increase chances for the emergence of favorable futures. In daily life, we are operating frequently with scenarios. For instance, when planning in spring for a children's birthday party next summer, we consider the scenarios of an outdoor party on a sunny day or an indoor party on a rainy day. Both scenarios are possible, plausible and internally consistent. Planning for a snowy day, on the other hand, is not considered, as this would be an inconsistent scenario. In climate research, scenarios have been widely used since the introduction of the IPCC process in the end of the 1980s (Houghton et al.These scenarios are built in a series of steps. This series begins with scenarios of page 1, Version 03/01/2007 Hans von Storch: Scenarios of future climate change