This document focuses primarily on the research planning for th4e U.S. Global Change Research Program for FY 1991. It is the second in a series of such documents that facilitates the coordination of the Program and reflects the research and integrated budget planning processes of the Working Group on Global Change of the Committee on Earth and Environmental Sciences (CEES), formerly the Committee on Earth Sciences (CES). ... The key emphasis in FY 1991 will be on establishing the research required to provide the scientific information needed as input to current environmental policy issues, e.g., stratospheric ozone depletion and climate change, including greenhouse warming. The opening sections of this document (pp. 1-20) summarize (i) these policy needs in the context of global change science, (ii) the planning of the research program to address them, and (iii) the benefits to be accrued from the enhanced understanding.