Chapter Outline

Summary for Policy Makers

Technical Summary

Chapter 1: Framing, context, methods

  • Executive Summary
  • Synthesis of key findings from AR5 and earlier assessment reports, and connections to AR6 Special Reports
  • Framing of the physical science information relevant for mitigation, adaptation, and risk assessment in the context of the Global Stocktake
  • Assessment approach
  • Observational and reanalysis developments since the AR5
  • Model and experimental design developments since the AR5
  • Emissions and forcing scenarios
  • Treatment and evaluation of uncertainty throughout the report
  • Frequently Asked Questions

Chapter 2: Changing state of the climate system

  • Executive Summary
  • Multi-millennial context, pre-industrial to present day
  • Natural and anthropogenic forcings
  • Radiative forcing
  • Large-scale indicators of observed change in the atmosphere, ocean, cryosphere, land, and biosphere
  • Modes of variability
  • Frequently Asked Questions

Chapter 3: Human influence on the climate system 

  • Executive Summary
  • Overview of model performance and development since the AR5
  • Simulated large-scale indicators of change in the atmosphere, ocean, cryosphere, land, and biosphere
  • Simulated modes of variability
  • Natural variability versus anthropogenically-forced change
  • Attribution of large-scale observed changes
  • Frequently Asked Questions

Chapter 4: Future global climate: scenario-based projections and near-term information 

  • Executive Summary
  • Projections of global mean surface temperature and other key global indicators
  • Evaluation of multi-model ensemble methods
  • Large scale patterns of climate change
  • Committed climate response, climate targets, overshoot, irreversibility, abrupt change
  • Climate response to greenhouse gas removal scenarios
  • Climate response to solar radiation management scenarios
  • Interplay between internal variability and response to forcings, including short-lived forcers
  • Variability and unexpected changes of global mean surface temperature
  • Near-term predictability, sources and capabilities
  • Synthesis of climate information in the near-term
  • Frequently Asked Questions

Chapter 5: Global carbon and other biogeochemical cycles and feedbacks 

  • Executive Summary
  • Feedbacks between climate and biogeochemical cycles, including paleoclimate information
  • Ocean acidification
  • Historical trends and variability of CO2, CH4 and N2O; sources and sinks
  • Projections of global biogeochemical cycles from near-term to long-term
  • Abrupt change, irreversibility
  • Model evaluation, emergent constraints
  • Transient climate response to cumulative emissions and remaining carbon budgets for climate targets
  • Biogeochemical implications of land and coastal management mitigation options and greenhouse gas removal
  • Biogeochemical implications of solar radiation management scenarios
  • Frequently Asked Questions

Chapter 6: Short-lived climate forcers

  • Executive Summary
  • Key emissions: global overview, natural, anthropogenic, historical and scenarios
  • Observed and reconstructed concentrations and radiative forcing
  • Direct and indirect-aerosol forcing
  • Implications for greenhouse gas lifetimes
  • Implications of different socio-economic and emission pathways, including urbanisation, for radiative forcing
  • Connections to air quality and atmospheric composition
  • Frequently Asked Questions

Chapter 7: The Earth's energy budget, climate feedbacks, and climate sensitivity

  • Executive Summary
  • Energy budget and its changes through time
  • Radiative forcing: definitions, estimates, and its representation in models
  • Climate feedbacks
  • Sensitivity of the climate system: methods and uncertainty
  • Empirical constraints on the sensitivity of the climate system, including paleoclimate
  • Global warming potential, global temperature change potential, and other metrics
  • Frequently Asked Questions

Chapter 8: Water cycle changes

  • Executive Summary
  • Observations, models, methods and their reliability
  • Past, present and projected changes, trends, variability and feedbacks in the physical components of the water cycle
  • Circulation, processes and phenomena (e.g. monsoon systems) affecting moisture and precipitation patterns, including extremes
  • Cloud-aerosol processes affecting the water cycle
  • Changes in seasonality of natural storage and water availability
  • Abrupt change
  • Confidence in projections
  • Frequently Asked Questions

Chapter 9: Ocean, cryosphere, and sea level change

  • Executive Summary
  • Past and future changes in ocean circulation and properties (trends, variability and extremes)
  • Past and future changes in marine and terrestrial cryosphere
  • Evaluation of models and projection methods
  • Detection and attribution
  • Past global and regional sea level changes
  • Projections of global and regional sea level change
  • Abrupt change and long-term commitment
  • Extreme water levels (tides, surge and ocean waves)
  • Frequently Asked Questions

Chapter 10: Linking global to regional climate change

  • Executive Summary
  • Regional phenomena, drivers, feedbacks and teleconnections
  • Regional scale observations and reanalyses
  • Interplay between internal variability and forced change at the regional scale, including attribution
  • Evaluation of model improvements, methods, including downscaling and bias adjustment and regional specificities
  • Confidence in regional climate information, including quantification of uncertainties
  • Scale specific methodologies e.g. urban, mountains, coastal, catchments, small islands
  • Approaches to synthesizing information from multiple lines of evidence
  • Frequently Asked Questions

Chapter 11: Weather and climate extreme events in a changing climate

  • Executive Summary
  • Extreme types, encompassing weather and climate timescales and compound events (including droughts, tropical cyclones)
  • Observations for extremes and their limitations, including paleo
  • Mechanisms, drivers and feedbacks leading to extremes
  • Ability of models to simulate extremes and related processes
  • Attribution of changes in extremes and extreme events
  • Assessment of projected changes of extremes and potential surprises
  • Case studies across timescales
  • Frequently Asked Questions

Chapter 12: Climate change information for regional impact and for risk assessment

  • Executive Summary
  • Framing: physical climate system and hazards
  • Region-specific integration of information, including confidence
  • Information (quantitative and qualitative) on changing hazards: present day, near term and long term
  • Region-specific methodologies
  • Relationship between changing hazards, global mean temperature change, scenarios and emissions
  • Frequently Asked Questions


  • Options for cross-WG integration including Regional Atlas
  • Cross Working Group Glossary
  • Technical Annexes
  • List of Acronyms
  • List of Contributors
  • List of Reviewers