This article discusees the main features of both the top-down and the bottom-up approcahes. The top down approach is problem-oriented, scienece driven and the parties jointly decide on emission-goals. As such this is seemingly a rather elegant approach and was long hailed as the best way to deal with the problem. In contrast the bottom-up approach is more pragmatic and not science driven as the parties define their goals and policies themselves. The down-side is that as climate measures are costly policies may be modest in the absence of international incentives to reduce emissions. However, in reality most approaches have elements of both top-down and bottom-up approaches. This, for example, applies to the many new more exclusive 'clubs' that have been established. As climate change is a very politically malign proiblem, institutional design of agrements cannot be expected to matter that much. However, in order to include as many countries as possible to real commitments a bottom-up approach may be necessary in the UNFCCC but then it is important that top-down review is effective as well.