This Synthesis Report with its Summary for Policymakers is the fourth and final part of the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC). It draws together and integrates for the benefit of policy makers, and others, and in response to questions identified by governments and subsequently agreed by the IPCC, information that has been approved and/ or accepted by the IPCC.¹ It is intended to assist governments, individually and collectively, in formulating appropriate adaptation and mitigation responses to the threat of human-induced climate change.

The Synthesis Report is based mainly on the contributions of the three IPCC Working Groups to the TAR, but also uses information from earlier IPCC assessments, Special Reports, and Technical Papers. It follows the question and answer format, and is in two parts: a Summary for Policymakers and a longer document that contains expanded responses to each of the questions posed by governments. The Summary for Policymakers references the appropriate paragraphs in the longer report, while the longer report contains references to the source of the material on which the response is based -- that is, the Summaries for Policymakers and chapters from previously approved and accepted Working Group contributions to the TAR and earlier IPCC reports and Technical Papers (see the accompanying box for cross-referencing nomenclature).

The procedures for approving the Summary for Policymakers and adopting the balance of the Synthesis Report were formalized by the IPCC at its Fifteenth Session (San Jose, Costa Rica, 15-18 April 1999). A draft of the Synthesis Report and its Summary for Policymakers was prepared by a team of lead authors, who were involved in preparation of the TAR, and submitted for simultaneous government/ technical and expert review. The revised drafts were circulated to governments in a final distribution before approval/ adoption at the IPCC's Eighteenth Session (Wembley, United Kingdom, 24- 29 September 2001).

The Synthesis Report consists of nine policy-relevant questions:

• Question 1 addresses the ultimate objective of the United Nations Framework Convention on Climate Change, which is found in Article 2 (i. e., what constitutes "dangerous anthropogenic interference in the climate system") and provides a framework for placing the issue of climate change in the context of sustainable development.
• Question 2 assesses and, where possible, attributes observed changes in climate and ecological systems since the pre-industrial era.
• Questions 3 and 4 assess the impact of future emissions of greenhouse gases and sulfate aerosol precursors (without specific policies to mitigate climate change) on climate, including changes in variability and extreme events and in ecological and socio-economic systems.
• Question 5 discusses inertia in the climate, ecological systems, and socio-economic sectors, and implications for mitigation and adaptation.
• Question 6 assesses the near-and long-term implications of stabilizing atmospheric concentrations of greenhouse gases on climate, ecological systems, and socio-economic sectors.
• Question 7 assesses the technologies, policies, and costs of near-and long-term actions to mitigate greenhouse gas emissions.
• Question 8 identifies the interactions between climate change, other environmental issues, and development.
• Question 9 summarizes the most robust findings and key uncertainties.

We take this opportunity to thank:

• The Core Writing Team who drafted this report and, with their meticulous and painstaking attention to detail, finalized it
• Other members of the IPCC Bureau who acted as Review Editors
• The members of the Working Groups' teams of Coordinating Lead Authors and Lead Authors who helped with the initial drafting
• The Heads and the staff of the Technical Support Units of the three Working Groups, particularly David Dokken, Maria Noguer, and Paul van der Linden for logistical and editorial support
• The Head and the staff of the GRID office at Arendal, Norway -- Philippe Rekacewicz in particular -- for working with the author team on the graphics contained in the Synthesis Report
• The staff of the IPCC Secretariat for innumerable administrative tasks performed.

The Synthesis Report with its Summary for Policymakers is published here in a single volume together with the Summaries for Policymakers and Technical Summaries of the Working Group contributions to the TAR, as well as a comprehensive, consolidated glossary. The Synthesis Report is also available in Arabic, Chinese, French, Russian, and Spanish -- the other official languages of the IPCC. The Synthesis Report is also available as a stand-alone publication, as are discrete brochures consisting of the Summaries for Policymakers, Technical Summaries, and glossaries of the respective Working Group reports. The full English text of all four volumes comprising the Third Assessment Report has been published in both print and digital form, with searchable versions available on cd-rom and at http://www.ipcc.ch.

R. T. Watson
IPCC Chair

N. Sundararaman
IPCC Secretary

IPCC Assessments Cited in the Synthesis Report
Qx.x	Relevant paragraph in the underlying Synthesis Report	SPM	Summary for Policymakers
WGI TAR	Working Group I contribution to the Third Assessment Report	TS	Technical Summary
WGII TAR	Working Group II contribution to the Third Assessment Report	ES	Executive Summary
WGIII TAR	Working Group III contribution to the Third Assessment Report	GP	Guidance Paper
SRES	Special Report on Emissions Scenarios	TP	Technical Paper
SRLULUCF	Special Report on Land Use, Land-Use Change, and Forestry
SRTT	Special Report on the Methodological and Technological Issues in Technology Transfer
SRAGA	Special Report on Aviation and the Global Atmosphere
DES GP	Guidance Paper on Development, Equity, and Sustainability
IPCC TP4	Technical Paper on Implications of Proposed CO2 Emissions Limitations
IPCC TP3	Technical Paper on Stabilization of Atmospheric Greehouse Gases: Physical, Biological, and Socio-Economic Implications
WGII SAR	Working Group II contribution to the Second Assessment Report

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