"Prepublication copy." Includes bibliographical references (pages 95-114) This study was supported by The U.S. Department of Energy under Contract Number DE-SC0011701, the National Aeronautics and Space Administration under Contract Number NNX13A041G, The National Oceanic and Atmospheric Administration under Contract Number WC133R-11-CQ-0048, The National Academy of Sciences, and the intelligence community.

Summary -- Introduction -- Carbon dioxide removal -- Assessment of possible carbon dioxide removal and long-term sequestration systems -- Social context -- Way forward -- References -- Appendices. The signals are everywhere that our planet is experiencing significant climate change. It is clear that we need to reduce the emissions of carbon dioxide and other greenhouse gases from our atmosphere if we want to avoid greatly increased risk of damage from climate change. Aggressively pursuing a program of emissions abatement or mitigation will show results over a timescale of many decades. How do we actively remove carbon dioxide from the atmosphere to make a bigger difference more quickly?