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NCA5 Logo
    • About This Report
    • Guide to the Report
    • Report Credits
    • Companion Podcast
    • Additional Resources
    • About this Report
    • Guide to this Report
    • OVERVIEW
    • Physical Science
    • 2. Climate Trends
    • 3. Earth Systems Processes
    • National Topics
    • 4. Water
    • 5. Energy
    • 6. Land
    • 7. Forests
    • 8. Ecosystems
    • 9. Coasts
    • 10. Oceans
    • 11. Agriculture
    • 12. Built Environment
    • 13. Transportation
    • 14. Air Quality
    • 15. Human Health
    • 16. Indigenous Peoples
    • 17. International
    • 18. Complex Systems
    • 19. Economics
    • 20. Social Systems and Justice
    • Regions
    • 21. Northeast
    • 22. Southeast
    • 23. US Caribbean
    • 24. Midwest
    • 25. Northern Great Plains
    • 26. Southern Great Plains
    • 27. Northwest
    • 28. Southwest
    • 29. Alaska
    • 30. Hawai'i and US-Affiliated Pacific Islands
    • Responses
    • 31. Adaptation
    • 32. Mitigation
    • Focus On
    • F1. Compound Events
    • F2. Western Wildfires
    • F3. COVID-19 and Climate Change
    • F4. Risks to Supply Chains
    • F5. Blue Carbon
    • Appendices
    • A1. Process
    • A2. Information Quality
    • A3. Scenarios and Datasets
    • A4. Indicators
    • A5. Glossary

    • All Figures
    • All Key Messages
    • View All Report Downloads
  • Art × Climate
  • NCA Atlas
  • EN ESPAÑOL
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Fifth National Climate Assessment
Physical Science

The Climate Trends and Earth Systems Processes chapters (Chs. 2, 3) assess how climate change affects physical Earth systems, with a focus on the United States, including observations and projections of climate change and discussion of how methods to understand changes in Earth systems have advanced since NCA4, which was released in November 2018.


  • Chapter 2. Climate Trends
  • Chapter 3. Earth Systems Processes

Likelihood

Virtually Certain Very Likely Likely As Likely as Not Unlikely Very Unikely Exceptionally Unlikely
99%–100% 90%–100% 66%–100% 33%–66% 0%–33% 0%–10% 0%–1%

Confidence Level

Very High High Medium Low
  • Strong evidence (established theory, multiple sources, well-documented and accepted methods, etc.)
  • High consensus
  • Moderate evidence (several sources, some consistency, methods vary and/or documentation limited, etc.)
  • Medium consensus
  • Suggestive evidence (a few sources, limited consistency, methods emerging, etc.)
  • Competing schools of thought
  • Inconclusive evidence (limited sources, extrapolations, inconsistent findings, poor documentation and/or methods not tested, etc.)
  • Disagreement or lack of opinions among experts

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