In order to make policy to response for climate change, it is essential to forecast future GHGs emissions in a long term. The IPCC decided at its 1996 plenary session to develop a new set of reference emission scenarios. Four modeling groups including us have startedto formulate the scenarios and test them for consistency in terms of both qualitative and quantitative factors with their models. In this paper, we describe one of the efforts, i. e. AIM quantification and its rationale.