Scenarios for future emissions are also beginning to be attempted, and will evolve rapidly during the next few years. Thus far only applied to greenhouse gas problems, one can envision the scenarios as tools for the study of future air quality, acid deposition, biodiversity, resource cycling, and the like. The overall GEIA effort is guided by the GEIA Steering Committee, which consists of A.F. Bouwman, D.M. Cunnold, T.E. Graedel, P.B. Middleton, and J.M. Pacyna. It is the opinion of the committee that few of the inventories now being released would have been compiled without the focus and organizing efforts of the IGAC program and the GEIA overview, management, and data distribution activities, and that those that would have been produced would not have had standardized formats and distribution mechanisms. We view the continuing GEIA effort as an exemplary example of the quality research that can result from an international collaborative effort in which resources of people, time, and funds are made available largely by participants' host institutions or countries.
Emissions inventories are the base on which many scientific studies rest.
Their quality and their availability have improved markedly during the past few years, especially so far as global, gridded inventories are concerned. Nonetheless, emissions inventories are, strictly speaking, never correct and never completed. In a world in which population, economic activity, and technology are constantly evolving, the construction and maintenance of reliable emissions inventories remains an effort in need of continuous financial support and the dedicated participation of outstanding scientists and engineers. Acknowledgements This report is based on the work of the GEIA inventory project teams. 185-208, NASA Ref.