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

Background

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)" 

• Cover (Front & Back)
• Front matters
• Policymakers Summary
• Introduction
• Chapter 1 - Greenhouse Gases and Aerosols
• Chapter 2 - Radiative Forcing of Climate
• Chapter 3 - Processes and Modelling
• Chapter 4 - Validation of Climate Models
• Chapter 5 - Equilibrium Climate Change - and its Implications for the Future
• Chapter 6 - Time-Dependent Greenhouse-Gas-Induced Climate Change
• Chapter 7 - Observed Climate Variations and Change
• Chapter 8 - Detection of the Greenhouse Effect in the Observations
• Chapter 9 - Sea Level Rise
• Chapter 10 - Effects on Ecosystems
• Chapter 11 - Narrowing the Uncertainties: A Scientific Action Plan for Improved Prediction of Global Climate Change
• Annex - Climatic consequences of emissions
• Appendix 1 - Emissions Scenarios from the Response Strategies Working Group of the IPCC
• Appendix 2 - Organisation of lPCC and WG I
• Appendix 3 - Contributors to IPCC WG I Report
• Appendix 4 - Reviewers of IPCC WG I Report
• Appendix 5 - Acronyms: Institutions
• Appendix 6 - Acronyms: Programmes & Miscellaneous
• Appendix 7 - Units
• Appendix 8 - Chemical Symbols
• Full Report (29,44 MB)

1992 Supplement

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

• Cover (Front & Back)
• Front matters
• The 1992 IPCC Supplement - Scientific Assessment
• Section A - Greenhouse Gases (title page)
•     Section A1 - Greenhouse Gases: Sources and Sinks
•     Section A2 - Radiative Forcing of Climate
•     Section A3 - Emissions Scenarios for the IPCC: an Update
• Section B - Climate Modelling, Climate Prediction and Model Validation
• Section C - Observed Climate Variability and Change
• Annex - Climatic consequences of emissions and comparison of IS92a and SA90
• Appendix 1 - Organization of IPCC and Working Group I
• Appendix 2 - Contributors to the IPCC Working Group I Report
• Appendix 3 - Reviewers of the IPCC Working Group I Report
• Appendix 4 - Acronyms
• Appendix 5 - Units
• Appendix 6 - Chemical Symbols

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"

• Summary
• Foreword
• Preface
• Summary for Policymakers
• Technical Summary
• 1 The Climate System: an Overview
• 2 Observed Climate Variability and Change
• 3 The Carbon Cycle and Atmospheric Carbon Dioxide
• 4 Atmospheric Chemistry and Greenhouse Gases
• 5 Aerosols, their Direct and Indirect Effects
• 6 Radiative Forcing of Climate Change
• 7 Physical Climate Processes and Feedbacks
• 8 Model Evaluation
• 9 Projections of Future Climate Change
• 10 Regional Climate Information - Evaluation and Projections
• 11 Changes in Sea Level
• 12 Detection of Climate Change and Attribution of Causes
• 13 Climate Scenario Development
• 14 Advancing Our Understanding
• Appendix I Glossary
• Appendix II SRES Tables
• Appendix III Contributors to the IPCC WGI Third Assessment Report
• Appendix IV Reviewers of the IPCC WGI Third Assessment Report
• Appendix V Acronyms and Abbreviations
• Appendix VI Units
• Appendix VII Some Chemical Symbols used in this Report
• Appendix VIII Figures and Tables in this Report

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

• Front Matter
• Summary for Policymakers
• Technical Summary
• Frequently Asked Questions (extracted from chapters below - for the public relating to common questions regarding climate change.)
• Chapter 1 Historical Overview of Climate Change Science
• Chapter 2 Changes in Atmospheric Constituents and in Radiative Forcing
• Chapter 3 Observations: Surface and Atmospheric Climate Change
• Chapter 4 Observations: Changes in Snow, Ice and Frozen Ground
• Chapter 5 Observations: Oceanic Climate Change and Sea Level
• Chapter 6 Palaeoclimate
• Chapter 7 Couplings Between Changes in the Climate System and Biogeochemistry
• Chapter 8 Climate Models and their Evaluation
• Chapter 9 Understanding and Attributing Climate Change
• Chapter 10 Global Climate Projections
• Chapter 11 Regional Climate Projections
• Annexes: (1) Glossary, (2) Authors, (3) Reviewers, (4) Acronyms
• Index
• Uncertainty Guidance Note for the Fourth Assessment Report
• Errata for the Working Group I Fourth Assessment Report
• Figures

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:

Further Reading:

• Inter-governmental Panel on Climate Change (IPCC)
• IPCC Working Group I
• AR4: WGI
• AR5: WGI