IPCC Working Group I

July 30, 2012, 2:42 pm
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IPCC Working Group I assesses the scientific aspects of the climate system and climate change for the Intergovernmental Panel on Climate Change (IPCC). It is responsible for producing reports as part of IPCC's multi-volume Assessments. IPCC Assessments with Working Group I reports were released in 1990, 1995, 2001, and 2007. The next Working Group I report (for Assessment Report 5 or "AR5") is scheduled to be finalized in September 2013. IPCC Working Group I is composed of an international group of scientists. Writing team membership for the Working Group II contribution to the AR5 consists of 259 Coordinating Lead Authors, Lead Authors, and Review Editors.

The reports of IPCC Working Groups have been among the most influential scientific reports on climate change


The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the World Meteorological Organization (WMO) and United Nations Environment Programme (UNEP) to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation. It is open to all Members of the United Nations and the WMO.

The IPCC work is shared among three Working Groups, a Task Force and a Task Group. The activities of each Working Group and of the Task Force are coordinated and administrated by a Technical Support Unit: Working Group I, Working Group II, Working Group III, and the Task Force on National Greenhouse Gas Inventiories.  Each of the groups are focused on a particular area relating to climate change. 

The IPCC Working Group I (WGI) assesses the physical scientific aspects of the climate system and climate change. The main topics assessed by WGI include: changes in greenhouse gases and aerosols in the atmosphere; observed changes in air, land and ocean temperatures, rainfall, glaciers and ice sheets, oceans and sea level; historical and paleoclimatic perspective on climate change; biogeochemistry, carbon cycle, gases and aerosols; satellite data and other data; climate models; climate projections, causes and attribution of climate change.

Working Group I Bureau

The WG I Bureau is responsible for organization of the Working Group.  The co-chairs of the WG I work with the co-chairs of the WG II (Impact and Adaptation), WG III (Mitigation), the Task Force on National Greenhouse Gas Inventories, and the IPCC chairs and vice-chairs to accomplish goals of the IPCC.

The Bureau consists of two co-chairs and six vice-chairs.  As of the date of this article, the two co-chairs for the WGI I Bureau are Thomas Stocker (Switzerland) and Dahe Qin (China).  The six vice-chairs are held by Jean Jouzel (France), Abdalah Mokssit (Morocco), Fatemah Rahimzadeh (Islamic Republic of Iran), Fredolin T. Tangang (Malaysia), David Wratt (New Zealand), and Francis Zwiers (Canada).

Assessment Reports

First Assessment Report (1990)

The Contribution of Working Group I to the First Assessment Report of the Intergovernmental Panel on Climate Change was "Climate Change: The IPCC Scientific Assessment (1990)" 

1992 Supplement

In 1992, Working Group I released "Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment"

Second Assessment Report (1995)

The Contribution of Working Group I to the Second Assessment Report of the Intergovernmental Panel on Climate Change was "Climate Change 1995: The Science of Climate Change" Full Report (PDF)

Third Assessment Report (2001)

The Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change was "Climate Change 2001: The Scientific Basis"

Fourth Assessment Report (2007)

The Contribution of Working Group I to the Fourth Assessment Report was "Climate Change 2007 - The Physical Science Basis" was launched on 2 February 2007 in Paris.

The report, described as "the most comprehensive and up-to-date scientifi c assessment of past, present and future climate change" includes information on changes in greenhouse gases and aerosols in the atmosphere and the extent to which they affect climate. It provides details of recent changes in air, land and ocean temperatures, rainfall, glaciers and ice sheets and considers a large amount of new satellite and other data that have not been assessed previously. A paleoclimatic perspective considers the Earth's past cold and warm periods and the understanding of climate processes that can be gained from these. New information on feedbacks arising from the interaction of climate change with the biosphere and geochemistry is also considered. The most recent climate models were evaluated in detail, as is their use to explain observed climate change in terms of different driving factors. Projections of future climate change using climate models are considered broadly and cover near term climate change, the degree to which this is 'committed' due to past increases in greenhouse gases, and a range of potential longer term climate changes. Patterns of future climate change are considered both globally and regionally.

Working Group I Report: The Physical Science Basis

Fifth Assessment Report

The IPCC Fifth Assessment Report (AR5) will provide an update of knowledge on the scientific, technical and socio-economic aspects of climate change, with all information contributed by select authors from each of the working groups and task forces.  WGI's contributions are based around their area of expertise, and will be focused around the "physical science basis" for climate change.  The outline of the WGI contribution to the AR5 was approved at the 11th Session of Working Group I and accepted by the 31st Session of the IPCC meeting in Bali, Indonesia, 26-29 October 2009.

The report by Working Group I to the multivolume Fifth Assessment Report (AR5) is scheduled for completion in September 2013 and to include the following:

Summary for Policy Makers
Technical Summary
Chapter 1: Introduction
Executive Summary
• Rationale and key concepts of the WG1 contribution
• Treatment of uncertainty
• Climate change projections since FAR
Frequently Asked Questions
Chapter 2: Observations: Atmosphere and Surface
Executive Summary
• Changes in surface temperature and soil temperature
• Changes in temperature, humidity and clouds
• Changes in atmospheric composition
• Changes in radiation fields and energy budget
• Changes in hydrology, runoff, precipitation and drought
• Changes in atmospheric circulation, including wind
• Spatial and temporal patterns of climate variability
• Changes in extreme events, including tropical and extratropical storms
Frequently Asked Questions
Chapter 3: Observations: Ocean
Executive Summary
• Changes in ocean temperature and heat content
• Ocean salinity change and freshwater fluxes
• Sea level change, ocean waves and storm surges
• Ocean biogeochemical changes, including ocean acidification
• Changes in ocean surface processes
• Changes in ocean circulation
• Spatial and temporal patterns of ocean variability
Frequently Asked Questions
Chapter 4: Observations: Cryosphere
Executive Summary
• Changes in ice sheets, including mass balance
• Changes in ice shelves
• Changes in glaciers and ice caps
• Sea ice variability and trends
• Snow and ice cover variability and trends
• Changes in frozen ground
• Dynamics of ice sheets, ice shelves, ice caps, glaciers and sea ice
Frequently Asked Questions
Chapter 5: Information from Paleoclimate Archives
Executive Summary
• Characteristics of early instrumental, documentary and natural climate archives
• Reconstruction of radiative forcing and climate response
• Reconstruction of regional variability and extremes
• Abrupt climate changes and their regional expression
• Sea level and ice sheets: patterns, amplitudes and rates of change
• Paleoclimate perspective on irreversibility in the climate system
• Paleodata-model intercomparisons
Frequently Asked Questions
Chapter 6:  Carbon and Other Biogeochemical Cycles
Executive Summary
• Past changes in CO2, CH4, N2O and biogeochemical cycles
• Recent trends in global and regional sources, sinks and inventories, including land use change
• Processes and understanding of changes, including ocean acidification
• Interactions between the carbon and other biogeochemical cycles, including the nitrogen cycle
• Projections of changes in carbon and other biogeochemical cycles
• Greenhouse gas stabilisation
• Carbon cycle – climate feedbacks and irreversibility
• Geoengineering involving the carbon cycle
Frequently Asked Questions
Chapter 7:  Clouds and Aerosols
Executive Summary
• Observations of clouds and their representation in models
• Coupling of clouds, water vapour, precipitation and the large-scale circulation
• Cloud and water vapour feedbacks and their effects on climate sensitivity
• Observations of aerosols and their representation in models
• Aerosol types including black carbon: chemistry, sources, sinks and distribution
• Direct and indirect aerosol forcing and effects, including contrails and cosmic rays
• Aerosol-cloud-precipitation interactions
• Geoengineering involving clouds and aerosols
Frequently Asked Questions
Chapter 8: Anthropogenic and Natural Radiative Forcing
Executive Summary
• Natural radiative forcing changes: solar and volcanic
• Anthropogenic radiative forcing, including effects from land surface changes
• Effects of atmospheric chemistry and composition
• Spatial and temporal expression of radiative forcing
• Greenhouse gas and other metrics, including Global Warming Potential (GWP)
and Global Temperature Change Potential (GTP)
Frequently Asked Questions
Chapter 9: Evaluation of Climate Models
Executive Summary
• The hierarchy of climate models: from global to regional
• Downscaling methods
• Assessing model performance, including quantitative measures and their use
• New model components and couplings
• Representation of processes and feedbacks in climate models
• Simulation of recent and longer term records
• Simulation of regional patterns, variability and extremes
Frequently Asked Questions
Chapter 10: Detection and Attribution of Climate Change: from Global to Regional
Executive Summary
• Evaluation of methodologies
• Atmospheric and surface changes
• Changes in ocean properties
• Cryosphere changes
• Extreme events
• Pre-instrumental perspective
• Implications of attribution for projections
Frequently Asked Questions
Chapter 11: Near-term Climate Change: Projections and Predictability
Executive Summary
• Predictability of interannual to decadal climate variations and change
• Projections for the next few decades
• Regional climate change, variability and extremes
• Atmospheric composition and air quality
• Possible effects of geoengineering
• Quantification of the range of climate change projections
Frequently Asked Questions
Chapter 12: Long-term Climate Change: Projections, Commitments and Irreversibility
Executive Summary
• Scenario description
• Projections for the 21st century
• Projections beyond the 21st century
• Regional climate change, variability and extremes
• Forcing, response and climate sensitivity
• Climate change commitment and inertia
• Potential for abrupt change and irreversibility in the climate system
• Quantification of the range of climate change projections
Frequently Asked Questions
Chapter 13: Sea Level Change
Executive Summary
• Synthesis of past sea level change and its components
• Models for sea level change
• Projections of globally averaged sea level rise
• Projections of the regional distribution of sea level change
• Extreme sea level events
• Potential ice sheet instability and its implications
• Multi-century projections
Frequently Asked Questions
Chapter 14: Climate Phenomena and their Relevance for Future Regional Climate Change
Executive Summary
• Patterns of variability: observations, understanding and projections
• Monsoon systems: observations, understanding and projections
• Extremes: observations, understanding and projections
• Interconnections among phenomena
Frequently Asked Questions
Annex I: Atlas of Global and Regional Climate Projections
Annex II: Glossary
Annex III: Acronyms and Regional Abbreviations
Annex IV: List of Authors
Annex V: List of Reviewers



Further Reading:




Mangino, K. (2012). IPCC Working Group I. Retrieved from


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