This work focuses on why climate change matters and is organized into two parts, devoted respectively to human and natural systems and regional aspects, incorporating results from the reports of Working Groups I and III. The volume addresses impacts that have already occurred and risks of future impacts, especially the way those risks change with the amount of climate change that occurs and with investments in adaptation to climate changes that cannot be avoided. For both past and future impacts, a core focus of the assessment is characterizing knowledge about vulnerability, the characteristics and interactions that make some events devastating, while others pass with little notice. Chapter 21. Regional Context -- Chapter 22. Africa -- Chapter 23. Europe -- Chapter 24. Asia -- Chapter 25. Australasia -- Chapter 26. North America -- Chapter 27. Central and South America -- Chapter 28. Polar regions -- Chapter 29. Small islands -- Chapter 30. The ocean -- Annex 1. Authors and Expert Reviewers -- Annex 2. Glossary -- Annex 3. Acronyms -- Annex 4. List of Major IPCC Reports.