Full Title: Climate Change 2013: The Physical Science Basis
Author(s): Workng Group I, Intergovernmental Panel on Climate Change
Publisher(s): Intergovernmental Panel on Climate Change
Publication Date: October 1, 2013
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Description (excerpt):
“Climate Change 2013: The Physical Science Basis” is the contribution of Working Group I to the Fifth
Assessment Report of the Intergovernmental Panel on Climate Change. This comprehensive assessment of
the physical aspects of climate change puts a focus on those elements that are relevant to understand past,
document current, and project future climate change. The assessment builds on the IPCC Fourth Assessment
Report (AR4) and the recent Special Report on Managing the Risk of Extreme Events and Disasters to
Advance Climate Change Adaptation (SREX) and is presented in 14 Chapters and 6 Annexes. The chapters
cover direct and proxy observations of changes in all components of the climate system, they assess the
current knowledge of various processes within, and interactions among, climate system components, which
determine the sensitivity and response of the system to changes in forcing, and they quantify the link
between the changes in atmospheric constituents, and hence radiative forcing, and the consequent detection and attribution of climate change. Projections of changes in all climate system components are based on
model simulations forced by a new set of scenarios. The report also provides a comprehensive assessment of
past and future sea level change in a dedicated chapter. Regional climate change information is presented in
the form of an Atlas of Global and Regional Climate Projections (Annex I). This is complemented by Annex
II: Climate System Scenario Tables and Annex III: Glossary.
The primary purpose of this Technical Summary is to provide the link between the complete assessment of
the multiple lines of independent evidence presented in the 14 chapters of the main report and the highly
condensed summary prepared as the WGI Summary for Policymakers. The Technical Summary thus serves
as a starting point for those readers who seek the full information on more specific topics covered by this
assessment. This purpose is facilitated by including pointers to the chapters and sections where the full
assessment can be found. Policy-relevant topics, which cut across many chapters and involve many
interlinked processes in the climate system, are presented here as Thematic Focus Elements, allowing rapid
access of this information.
An integral element of this report is the use of uncertainty language that permits a traceable account of the
assessment (see Box TS.1). The degree of certainty in key findings in this assessment is based on the author
teams’ evaluations of underlying scientific understanding and is expressed as a level of confidence that
results from the type, amount, quality, and consistency of evidence and the degree of agreement in the
scientific studies considered. Confidence is expressed qualitatively. Quantified measures of uncertainty in a
finding are expressed probabilistically and are based on a combination of statistical analyses of observations
or model results, or both, and expert judgment. Where appropriate, findings are also formulated as
statements of fact without using uncertainty qualifiers (See Chapter 1 and Box TS.1 for more details).