Figure CB9.1 — Special Report on the Ocean and Cryosphere in a Changing Climate

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Figure CB9.1

Figure CB9.1 | The global distribution of low-lying islands and coasts (LLIC) particularly at risk from sea level rise This map considers the Low Elevation Coastal Zone (elevation data from National Geophysical Data Center, 1999; LECZ, defined by McGranahan et al., 2007), islands with a maximum elevation of 10 m above sea level (Weigelt et al., 2013), Small Island Developing States (SIDS; UN-OHRLLS, n.d.), coastal megacities (cities with more than 10 million inhabitants, within 100 km from coast, and maximum 50 m above sea level; Pelling and Blackburn, 2013; UN-DESA, 2018) and deltas (Tessler et al., 2015). Regional sea level changes refer to projections under Representative Concentration Pathway(RCP)8.5 (2081–2100) (see Figure 4.8).

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SPM

Chapter T

Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter CB9

Glossary

Summary for Policymakers

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IIntroduction
AObserved changes and impacts
BProjected changes and risks
CImplementing responses to ocean and cryosphere change
+Citation

Technical Summary

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TS.0Introduction
TS.1 Framing and Context of the Report
TS.2High Mountain Areas
TS.3Polar Regions
TS.4Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities
TS.5Changing Ocean, Marine Ecosystems, and Dependent Communities
TS.6Extremes, Abrupt Changes and Managing Risks
TS.7Low-lying Islands and Coasts (Integrative Cross-Chapter Box)
CCitation

Framing and Context of the Report

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ESExecutive Summary
1.1Why this Special Report?
1.2 Role of the Ocean and Cryosphere in the Earth System
- 1.2.1Ocean and Cryosphere in Earth’s Energy, Water and Biogeochemical Cycles
- 1.2.2Interactions Between the Ocean and Cryosphere
1.3 Time Scales, Thresholds and Detection of Ocean and Cryosphere Change
1.4 Changes in the Ocean and Cryosphere
- 1.4.1Observed and Projected Changes in the Ocean
- 1.4.2Observed and Projected Changes in the Cryosphere
1.5 Risk and Impacts Related to Ocean and Cryosphere Change
1.6Addressing the Causes and Consequences of Climate Change for the Ocean and Cryosphere
- 1.6.1 Mitigation and Adaptation Options in the Ocean and Cryosphere
- 1.6.2Adaptation in Natural Systems, Ecosystems, and Human Systems
1.7 Governance and Institutions
1.8 Knowledge Systems for Understanding and Responding to Change
- 1.8.1Scientific Knowledge
  - 1.8.1.1 Ocean and Cryosphere Observations
  - 1.8.1.2Reanalysis Products
  - 1.8.1.3Model Simulation Data
  - 1.8.1.4 Palaeoclimate Data
- 1.8.2Indigenous Knowledge and Local Knowledge
- 1.8.3The Role of Knowledge in People’s Responses to Climate, Ocean and Cryosphere Change
1.9Approaches Taken in this Special Report
- 1.9.1Methodologies Relevant to this Report
- 1.9.2Communication of Confidence in Assessment Findings
1.10Integrated Storyline of this Special Report
AAcknowledgements
CCitation
SMSupplementary Material

High Mountain Areas

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ESExecutive Summary
2.1Introduction
2.2Changes in the Mountain Cryosphere
- 2.2.1Atmospheric Drivers of Changes in the Mountain Cryosphere
  - 2.2.1.1Surface Air Temperature
  - 2.2.1.2Rainfall and Snowfall
  - 2.2.1.3 Other Meteorological Variables
- 2.2.2Snow Cover
- 2.2.3Glaciers
- 2.2.4Permafrost
- 2.2.5Lake and River Ice
2.3 Mountain Social-Ecological Systems: Impacts, Risks and Human Responses
- 2.3.1Water Resources
  - 2.3.1.1Changes in River Runoff
  - 2.3.1.2 Water Quality
  - 2.3.1.3 Key Impacts and Vulnerability
  - 2.3.1.4 Water Governance and Response Measures
- 2.3.2Landslide, Avalanche and Flood Hazards
  - 2.3.2.1 Observed and Projected Changes
  - 2.3.2.2 Exposure, Vulnerability and Impacts
  - 2.3.2.3 Disaster Risk Reduction and Adaptation
- 2.3.3Ecosystems
  - 2.3.3.1 Terrestrial Biota
  - 2.3.3.2 Freshwater Biota
  - 2.3.3.3 Ecosystem Services and Adaptation
- 2.3.4Infrastructure and Mining
- 2.3.5Tourism and Recreation
- 2.3.6Cultural Values and Human Well-being
- 2.3.7Migration, Habitability and Livelihoods
2.4 International Policy Frameworks and Pathways to Sustainable Development
2.5 Key Gaps in Knowledge and Prospects
AAcknowledgements
A.2.A Additional Information on Global and Regional Glacier Mass Change Estimates for 2006–2015
CCitation
+Acknowledgements
SMSupplementary Material

Polar regions

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ESExecutive Summary
3.1Introduction: Polar Regions, People and the Planet
3.2 Sea Ice and Polar Oceans: Changes, Consequences and Impacts
- 3.2.1Observed Changes in Sea Ice and Ocean
  - 3.2.1.1Sea Ice
  - 3.2.1.2Ocean Properties
  - 3.2.1.3Ocean Circulation
- 3.2.2Projected Changes in Sea Ice and Ocean
  - 3.2.2.1Sea Ice
  - 3.2.2.2Physical Oceanography
  - 3.2.2.3Carbon and Ocean Acidification
- 3.2.3Impacts on Marine Ecosystems
  - 3.2.3.1Arctic
  - 3.2.3.23.2.3.2 Southern Ocean
- 3.2.4Impacts on Social-Ecological Systems
  - 3.2.4.1Fisheries
  - 3.2.4.2Tourism
  - 3.2.4.3Transportation
3.3Polar Ice Sheets and Glaciers: Changes, Consequences and Impacts
- 3.3.1Ice Sheet Changes
  - 3.3.1.1Antarctic Ice Sheet Mass Change
  - 3.3.1.2Components of Antarctic Ice Sheet Mass Change
  - 3.3.1.3Greenland Ice Sheet Mass Change
  - 3.3.1.4Components of Greenland Ice Sheet Mass Change
  - 3.3.1.5Drivers of ice sheet mass change
  - 3.3.1.6Natural and Anthropogenic Forcing
  - 3.3.1.7Ice sheet projections
- 3.3.2Polar Glacier Changes
  - 3.3.2.1Observations, Components of Change, and Drivers
  - 3.3.2.2Projections
- 3.3.3Consequences and Impacts
  - 3.3.3.1Sea Level
  - 3.3.3.2Physical Oceanography
  - 3.3.3.3Biogeochemistry
  - 3.3.3.4Ecosystems
3.4Arctic Snow, Freshwater Ice and Permafrost: Changes, Consequences and Impacts
- 3.4.1Observations
  - 3.4.1.1 Seasonal Snow Cover
  - 3.4.1.2 Permafrost
  - 3.4.1.3 Freshwater Systems
- 3.4.2Projections
  - 3.4.2.1 Seasonal Snow
  - 3.4.2.2Permafrost
  - 3.4.2.3Freshwater Systems
- 3.4.3 Consequences and Impacts
  - 3.4.3.1 Global Climate Feedbacks
  - 3.4.3.2 Ecosystems and their Services
  - 3.4.3.3Impacts on Social-Ecological Systems
3.5Human Responses to Climate Change in Polar Regions
- 3.5.1The Polar Context for Responding
- 3.5.2Responses of Human Sectors
  - 3.5.2.1 Commercial Fisheries
  - 3.5.2.2 Arctic Subsistence Systems
  - 3.5.2.3Arctic Reindeer Herding
  - 3.5.2.4Tourism
  - 3.5.2.5Arctic Non-Renewable Extractive Industries
  - 3.5.2.6Infrastructure
  - 3.5.2.7 Marine Transportation
  - 3.5.2.8Arctic Human Health and Well Being
- 3.5.3Governance
  - 3.5.3.1 Local to National Governance
  - 3.5.3.2International Climate Governance and Law: Implications for International Cooperation
- 3.5.4Towards Resilient Pathways
  - 3.5.4.1Knowledge Co-production and Integration
  - 3.5.4.2Linking Knowledge with Decision Making
  - 3.5.4.3Resilience-based Ecosystem Stewardship
3.6 Synopsis
3.7 Key Knowledge Gaps and Uncertainties
+Acknowledgements
CCitation
SMSupplementary Material

Sea Level Rise and Implications for Low-Lying Islands, Coasts and Communities

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DDownload Chapter 4
ESExecutive Summary
4.1Synthesis
4.2Physical Basis for Sea Level Change and Associated Hazards
- 4.2.1Processes of Sea Level Change
  - 4.2.1.1Ice Sheets and Ice Shelves
  - 4.2.1.2Glaciers
  - 4.2.1.3Ocean Processes
  - 4.2.1.4Terrestrial Reservoirs
  - 4.2.1.5Geodynamic Processes
  - 4.2.1.6Extreme Sea Level Events
- 4.2.2Observed Changes in Sea Level (Past and Present)
- 4.2.3Projections of Sea Level Change
  - 4.2.3.1Contribution of Ice Sheets to GMSL
  - 4.2.3.2Global and Regional Projections of Sea Level Rise
  - 4.2.3.3Probabilistic Sea Level Projections
  - 4.2.3.4Changes in Extreme Sea Level events
  - 4.2.3.5 Long-Term Scenarios, Beyond 2100
4.3 Exposure, Vulnerability, Impacts and Risk Related to Sea Level Rise
- 4.3.1Introduction
- 4.3.2Dimensions of Exposure and Vulnerability to Sea Level Rise
  - 4.3.2.1Point of Departure
  - 4.3.2.2Settlement Trends
  - 4.3.2.4Other Human Dimensions
  - 4.3.2.5 Towards a Synthetic Understanding of the Drivers of Exposure and Vulnerability
  - 4.3.2.3Terrestrial Processes Shaping Coastal Exposure and Vulnerability
- 4.3.3Observed Impacts, and Current and Future Risk of Sea Level Rise
  - 4.3.3.6Human Activities
  - 4.3.3.1Attribution of Observed Physical Changes to Sea Level Rise
  - 4.3.3.2Submergence and Flooding of Coastal Areas
  - 4.3.3.3Coastal Erosion and Projected Global Impacts of Enhanced Erosion on Human Systems
  - 4.3.3.4Salinisation
  - 4.3.3.5Ecosystems and Ecosystem Services
- 4.3.4 Conclusion on Coastal Risk: Reasons for Concern and Future Risks
  - 4.3.4.1 Methodological Advances
  - 4.3.4.2 Key Findings on Future Risks and Adaptation Benefits
4.4.Responding to Sea Level Rise
- 4.4.1Introduction
- 4.4.2Observed and Projected Responses, their Costs, Benefits, Co-benefits, Drawbacks, Efficiency and Governance
  - 4.4.2.1Types of Responses and Framework for Assessment
  - 4.4.2.2Hard and Sediment-Based Protection
  - 4.4.2.3Ecosystem-based Adaptation
  - 4.4.2.4Advance
  - 4.4.2.5Accommodation
  - 4.4.2.6Retreat
- 4.4.3Governance challenges in responding to sea level rise
  - 4.4.3.1Introduction
  - 4.4.3.2Understanding Barriers to Adaptation as Governance Challenges
  - 4.4.3.3Governance Challenges in the Face of Sea Level Rise
- 4.4.4Planning, Engagement and Decision Tools for Choosing Responses
  - 4.4.4.1 Introduction
  - 4.4.4.2Planning, Public Participation and Conflict Resolution in the Face of SLR
  - 4.4.4.3Decision Analysis Methods
- 4.4.5Enabling Conditions and Lessons Learned From ‘Practice’
- 4.4.6Towards Climate Resilient Development Pathways
CCitation
SMSupplementary Material

Changing Ocean, Marine Ecosystems, and Dependent Communities

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ESExecutive Summary
5.1 Introduction
5.2 Changing Ocean and Biodiversity
- 5.2.1Introduction
- 5.2.2Changes in Physical and Biogeochemical Properties
  - 5.2.2.1Introduction to Changing Open Ocean
  - 5.2.2.2 Changing Temperature, Salinity, Circulation
  - 5.2.2.3 Changes in Ocean Carbon
  - 5.2.2.4Changing Ocean Oxygen
  - 5.2.2.5Changing Ocean Nutrients
  - 5.2.2.6Changing Ocean Primary and Export Production
- 5.2.3Impacts on Pelagic Ecosystems
  - 5.2.3.1 The Epipelagic Ocean
  - 5.2.3.2 The Deep Pelagic Ocean
- 5.2.4Impacts on Deep Seafloor Systems
  - 5.2.4.1Changes on the Deep Seafloor
  - 5.2.4.2Open Ocean Seafloor - Abyssal Plains (3000-6000 m)
  - 5.2.4.3Bathyal Ecosystems (200–3000 m)
  - 5.2.4.4Chemosynthetic Ecosystems
- 5.2.5Risk Assessment of Open Ocean Ecosystems
5.3 Changing Coastal Ecosystems and Biodiversity
- 5.3.1Estuaries
- 5.3.2Coastal Wetlands (Salt Marshes, Seagrass Meadows and Mangrove Forests)
- 5.3.3Sandy Beaches
- 5.3.4Coral Reefs
- 5.3.5Rocky Shores
- 5.3.6Kelp Forests
- 5.3.7Risk Assessment for Coastal Ecosystems
5.4 Changing Marine Ecosystem Services and Human Well-being
- 5.4.1Changes in Key Ecosystem Services
  - 5.4.1.1Provisioning Services
  - 5.4.1.2 Regulating Services
  - 5.4.1.3 Supporting Services
  - 5.4.1.4 Cultural Services
- 5.4.2Climate Risk, Vulnerability and Exposure of Human Communities and their Well-being
  - 5.4.2.1 Human Health and Environmental Health
  - 5.4.2.2Cultural and Other Social Dimensions
  - 5.4.2.3Monetary and Material Wealth
  - 5.4.2.4Risk and Opportunities for Ocean Economy
  - 5.4.2.5Impacts of Changing Ocean on Sustainable Development Goals
5.5 Risk-reduction Responses and their Governance
- 5.5.1Ocean-based Mitigation
  - 5.5.1.1Context for Blue Carbon and Overview Assessment
  - 5.5.1.2 Climate Mitigation in the Coastal Ocean
  - 5.5.1.3 Climate Mitigation in the Open Ocean
- 5.5.2Ocean-based Adaptation
  - 5.5.2.1Ecosystem-based Adaptation
  - 5.5.2.2Human Systems
  - 5.5.2.3Ocean-based Climate Change Adaptation Frameworks
  - 5.5.2.4The Role of Education and Local Knowledge in Adapting to Climate Change.
  - 5.5.2.5Costs and Limits for Coastal Climate Change Adaptation
  - 5.5.2.6Summary
- 5.5.3Governance Across All Scales
5.6 Synthesis
5.7 Key Uncertainties and Gaps
CCitation
SMSupplementary Material

Extremes, Abrupt Changes and Managing Risks

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ESExecutive Summary
6.1 Introduction
- 6.1.1Definitions of Principal Terms
6.2 Climate Change influences on Abrupt Changes, Irreversibility, Tipping Points and Extreme Events
- 6.2.1Introduction
- 6.2.2Recent Anomalous Extreme Climate Events and their Causes
6.3 Changes in Tracks, Intensity, and Frequency of Tropical and Extratropical Cyclones and Associated Sea Surface Dynamics
- 6.3.1Changes in Storms and Associated Sea Surface Dynamics
  - 6.3.1.1Tropical Cyclones
  - 6.3.1.2 Extratropical Cyclones and Blocking
  - 6.3.1.3 Waves and Extreme Sea Levels
- 6.3.2Impacts
- 6.3.3Risk Management and Adaptation
6.4 Marine Heatwaves and their Implications
- 6.4.1Observations and Key Processes, Detection and Attribution, Projections
  - 6.4.1.1 Recent Documented MHWs and Key Driving Mechanisms
  - 6.4.1.2 Detection and Attribution of MHW Events
  - 6.4.1.3 Future Changes
- 6.4.2Impacts on Natural, Physical and Human Systems
  - 6.4.2.1 Impacts on Marine Organisms and Ecosystems
  - 6.4.2.2Impacts on the Physical System
  - 6.4.2.3Impacts on the Human System
- 6.4.3Risk Management and Adaptation, Monitoring and Early Warning Systems
6.5 Extreme ENSO Events and Other Modes of Interannual Climate Variability
6.6 Inter-Ocean Exchanges and Global Change
- 6.6.1Key Processes and Feedbacks, Observations, Detection and Attribution, Projections
- 6.6.2Impacts on Natural and Human Systems
6.7 Risks of Abrupt Change in Ocean Circulation and Potential Consequences
6.8 Compound Events and Cascading Impacts
- 6.8.1Concepts
- 6.8.2Multiple Hazards
- 6.8.3Cascading Impacts on Ecosystems
- 6.8.4Cascading Impacts on Social Systems
- 6.8.5Risk Management and Adaptation, Sustainable and Resilient Pathways
- 6.8.6Global Impact of Tipping Points
6.9 Governance and Policy Options, Risk Management, Including Disaster Risk Reduction and Enhancing Resilience
- 6.9.1Decision Making for Abrupt Change and Extreme Events
- 6.9.2Transformative Governance and Integrating Disaster Risk Reduction and Climate Change Adaptation
6.10Knowledge Gaps
CCitation

Integrative Cross-Chapter Box on Low-lying Islands and Coasts

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ESExecutive Summary
IIntroduction
DDrivers of Impacts and Risks
OObserved and Projected Impacts on Geographies and Major Sectors
RResponses: Adaptation Strategies in Practice
CConclusions
CCitation

Glossary

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