This document reports on a workshop held in December 2010 in Arlington, Virginia to explore needs, options, and research for the development of scenarios to support science and assessment of climate and global change over the coming decades. The overall effort was led by the science community and coordinated through a research community steering group. Responding to the interagency U.S. Global Change Research Program (USGCRP), the workshop was sponsored by the U.S. Department of Energy's Office of Biological and Environmental Research. The purpose, scope, and objectives of the effort were informed by inputs from a federal coordinating committee comprised of representatives of participating USGCRP agencies. The workshop brought together leading researchers, scenario developers, stakeholders, and federal officials to examine the potential uses of scenarios in research on and assessments of climate change and response options. The results also have significant implications for climate research beyond assessments, improving understanding of the current scientific basis for scenario development and identifying methods for improving consistency in their use and interpretation. The workshop included plenary-session presentations and panels as well as breakout group discussions.