This document is part of the information upon which the Parties to the United Nations Montreal Protocol will base their future decisions regarding ozone-depleting substances, their alternatives, and protection of the ozone layer. It is the latest in a long series of scientific assessments that have informed the Parties and contains the policy-relevant major findings of the Assessment's five scientific chapters. Actions taken under the Montreal Protocol have led to decreases in the atmospheric abundance of controlled ozone-depleting substances (ODSs), and are enabling the return of the ozone layer toward 1980 levels. This comprehensive volume includes many tables, figures, and charts throughout; and the appendices include acronyms and abbreviations, listings of authors, contributors, and reviewers from around the world, and chemical formulas. Related products: NASA and the Environment: The Case of Ozone Depletion is available here: https://bookstore.gpo.gov/products/nasa-and-environment-case-ozone-depletion Code of Federal Regulations, Title 40, Protection of Environment, Pt. 96-99, Revised as of July 1, 2016 can be found here: https://bookstore.gpo.gov/products/code-federal-regulations-title-40-protection-environment-pt-96-99-revised-july-1-2016 Our Changing Atmosphere: Discoveries from EOS Aura (Booklet) -reduced list price while supplies last available here: https://bookstore.gpo.gov/products/our-changing-atmosphere-discoveries-eos-aura-booklet