Warming of the climate system is unequivocal, human influence on the climate system is clear, and limiting climate change will require substantial and sustained reductions of greenhouse gas emissions. These are the key conclusions from an assessment by the Intergovernmental Panel on Climate Change (IPCC) that was released on Thursday in its full and finalised form.
The Summary for Policymakers of the IPCC Working Group I assessment report, “Climate Change 2013: the Physical Science Basis,” was approved in September 2013 by the member governments of the IPCC meeting in Stockholm, Sweden, who also accepted the underlying report, after which the Summary for Policymakers was immediately made public.
The full report is the basis for the key conclusions presented in the Summary for Policymakers. This Working Group I contribution to the IPCC’s Fifth Assessment Report offers a comprehensive understanding of the physical science basis of climate change. Policymakers, stakeholders and the scientific community are now able to use and apply the detailed information on which IPCC Working Group I bases its assessment. Additional material documents the IPCC assessment process with its multiple rounds of drafting and review.
“The Working Group I Fifth Assessment Report, which has over 1,500 printed pages of text and includes more than 600 printed diagrams, provides a comprehensive assessment of the physical science basis of climate change, citing more than 9000 scientific publications. The report provides information about what has changed in the climate system, why it has changed, and how it will change in the future,” said Thomas Stocker, Co-Chair of IPCC Working Group I.
The full report consists of the Summary for Policymakers, a longer Technical Summary, 14 chapters and six annexes including an Atlas of Global and Regional Climate Projections. The Atlas is an innovation in this Working Group I assessment, containing time series and maps of temperature and precipitation projections for 35 regions of the world, which enhance accessibility for stakeholders and users. As well as the printed Atlas, there are four sets of Atlas Supplementary Material with 155 figures each, and the data underlying the Atlas figures will also be made available as part of the launch.
Another innovative feature of this report is the presentation of Thematic Focus Elements in the Technical Summary that provide end-to-end assessments of important cross-cutting issues for understanding the physical science basis of climate change, such as water cycle change, irreversibility and abrupt change, climate sensitivity and feedbacks, climate targets and stabilisation.
All chapters contain Frequently Asked Questions in which the authors provide scientific answers to a range of general questions in an accessible form.
In order to document the drafting and review process, the IPCC is making public the earlier drafts of the report that were subject to formal review, all 54,677 written review comments by expert and government reviewers on those drafts and the responses by the authors to the comments. All figures from the Summary for Policymakers, the Technical Summary, and from the 14 Chapters of the report are also being made available electronically in order to facilitate outreach and communications activities that wish to highlight IPCC findings. Extensive Supplementary Material can be accessed online and includes description of datasets, models, or methodologies used in some chapters of the assessment. Background information on all the figures in the Summary for Policymakers is provided in the Supplementary Material to the Technical Summary.
“I would like to thank the hundreds of scientists and experts around the world who served as authors and review editors for producing a comprehensive and scientifically robust assessment. I also express my thanks to the more than one thousand expert reviewers for contributing their expertise in the preparation of this assessment,” said Qin Dahe, the other Co-Chair of WGI, from Beijing, China.