Acknowledgements -- Abbreviations and Acronyms -- 1. Summary for Decision Makers -- Part 1. Context. 2. Overview -- 3. The Changing Southwest -- Part 2. Weather and Climate of the Southwest. 4. Present Weather and Climate: Average Conditions -- 5. Present Weather and Climate: Evolving Conditions -- 6. Future Climate: Projected Average -- 7. Future Climate: Projected Extremes -- Part 3. Effects of Climate Change in the Southwest. 8. Natural Ecosystems -- 9. Coastal Issues -- 10. Water: Impacts, Risks, and Adaptation -- 11. Agriculture and Ranching -- 12. Energy: Supply, Demand, and Impacts -- 13. Urban Areas -- 14. Transportation -- 15. Human Health -- 16. Climate Change and U.S.-Mexico Border Communities -- 17. Unique Challenges Facing Southwestern Tribes -- Part 4. Options and Research Needs. 18. Climate Choices for a Sustainable Southwest -- 19. Moving Forward with Imperfect Information -- 20. Research Strategies for Addressing Uncertainties -- References -- Glossary -- Author and Review Editors -- Reviewers.