IPCC Sixth Assessment Report

IPCC Sixth Assessment Report
Name	IPCC Sixth Assessment Report
Date	2021–2023
Publisher	Intergovernmental Panel on Climate Change
Subject	climate change assessment

IPCC Sixth Assessment Report The Sixth Assessment Report is a multi-volume appraisal of climate science produced between 2021 and 2023 by the Intergovernmental Panel on Climate Change. It synthesizes evidence from observational records, paleoclimate reconstructions, climate models, and sectoral studies to inform negotiations and decisions in forums such as United Nations Framework Convention on Climate Change, COP26, and national policy processes. The report integrates contributions from experts affiliated with institutions like NASA, NOAA, European Commission, Met Office, and universities including University of Oxford and Massachusetts Institute of Technology.

Background and development

The report was prepared under the oversight of the Intergovernmental Panel on Climate Change, an organization founded after assessments such as the Assessment Reports by the IPCC and international processes including the Rio Earth Summit and the Kyoto Protocol. Scoping and drafting involved lead authors from agencies including National Center for Atmospheric Research, Geological Survey of Japan, Chinese Academy of Sciences, and research centers such as Potsdam Institute for Climate Impact Research and Tyndall Centre. Review cycles included expert review panels drawn from World Meteorological Organization, United Nations Environment Programme, European Space Agency, and national academies like the Royal Society and the National Academy of Sciences (United States). Publication timing intersected with events including COVID-19 pandemic responses and international diplomacy at G7 summit meetings.

Working Group contributions and structure

The assessment comprised three Working Groups and a Synthesis Report, mirroring the structure used in prior exercises such as the Fifth Assessment Report process. Working Group I focused on physical science contributions from teams linked to Met Office Hadley Centre, Max Planck Institute for Meteorology, Lawrence Livermore National Laboratory, and CSIRO. Working Group II addressed impacts, adaptation, and vulnerability drawing on studies from World Bank, Asian Development Bank, Inter-American Development Bank, and consortia at University of Cape Town and Indian Institute of Science. Working Group III assessed mitigation pathways with input from modelers at International Energy Agency, Rocky Mountain Institute, Fraunhofer Society, and laboratories at Argonne National Laboratory. The Synthesis Report integrated assessments used by stakeholders such as European Union, African Union, Association of Southeast Asian Nations, and Small Island Developing States delegates in policy fora.

Key findings and synthesis

The report reported high confidence in observed warming trends documented in datasets maintained by HadCRUT, Berkeley Earth, GISTEMP, and reconstructions linked to PAGES 2k Consortium. It attributed major recent changes to anthropogenic forcing described by researchers at IPSL, NCAR, and NOAA ESRL. Projections evaluated coupled model ensembles from CMIP6 centers including MPI-ESM1.2, UKESM1, and CESM2 and explored scenarios informed by narratives such as those from the Shared Socioeconomic Pathways framework used by IIASA and IIASA SSP Database. The synthesis emphasized risks highlighted in sectoral literature involving International Maritime Organization shipping impacts, Food and Agriculture Organization crop studies, World Health Organization health burdens, and infrastructure analyses by Asian Development Bank. It underscored thresholds noted in paleoclimate records related to events like the Younger Dryas and cited mitigation cost estimates by OECD and technology assessments from International Renewable Energy Agency.

Regional and sectoral impacts

Regional chapters synthesized evidence for continents and basins studied by teams at institutes such as CSIRO for Australasia, Instituto de Hidrología, Meteorología y Estudios Ambientales for South America, Norwegian Institute for Water Research for Arctic systems, and Center for Climate Systems Research for North America. Impacts on sectors were drawn from industry and NGO studies including analyses by International Energy Agency on energy, International Civil Aviation Organization on aviation, International Labour Organization on labor productivity, and UNESCO on cultural heritage. Case studies referenced events such as the European heat wave of 2003, Australian bushfire season 2019–20, and Hurricane Maria to illustrate exposure and vulnerability across coastal, mountain, and urban systems studied by UN-Habitat and World Resources Institute.

Mitigation strategies and policy implications

The report evaluated mitigation options spanning renewables and efficiency pathways assessed by International Renewable Energy Agency, National Grid ESO, and research teams at Duke University and Tsinghua University. It examined carbon removal technologies reviewed by Royal Society panels and governance mechanisms discussed at UNFCCC sessions, including market and non-market approaches featured in instruments like the Paris Agreement and deliberations in Glasgow Climate Pact. Policy implications highlighted transitions in energy systems, transport modalities analyzed by International Transport Forum, land-use shifts covered by Food and Agriculture Organization, and finance mobilization involving actors such as World Bank Group, Green Climate Fund, and sovereign entities like European Investment Bank.

Assessment of uncertainties and methods

Uncertainty treatment built on methodologies from ensembles in CMIP6, statistical approaches used by Hadley Centre, and detection-attribution frameworks developed at NOAA and Lawrence Berkeley National Laboratory. The report discussed epistemic and aleatory sources informed by paleoclimate analogs from International Ocean Discovery Program and observational gaps addressed by missions from NASA Earth Observatory and Copernicus Programme. Methods sections referenced scenario analysis using Integrated Assessment Models developed by teams at IIASA, Princeton University, and Potsdam Institute for Climate Impact Research and highlighted model intercomparison exercises such as those coordinated by Coupled Model Intercomparison Project. Evaluations included probability language standardized through guidance from World Meteorological Organization and peer-review protocols adopted from major academies including the Royal Society.

Category:Climate reports