Review in the IPCC process
“Review is an essential part of the IPCC process. Since the IPCC is an intergovernmental body, review of IPCC documents should involve both peer review by experts and review by governments.”
Every IPCC report goes through several drafts and reviews to ensure it is as robust, comprehensive and balanced as possible.
The review process is critical for ensuring the assessment is scientifically rigorous, exhaustive, objective and transparent; broad participation in the IPCC review process is one of the core strengths of IPCC assessments.
The First-Order Draft is open to review by experts; the Second-Order Draft is reviewed by governments and experts; and governments send comments on the Summary for Policymakers, and the Overview Chapter in the case of a Methodology Report, during the Final Government Distribution. In the case of a Synthesis Report draft, it undergoes a single simultaneous government and expert review; followed by a government review of the final draft through the Final Government Distribution.
All review comments submitted by experts or governments are addressed by the authors. The comments and the author responses, together with the drafts, are published after the report is finalized.
How do experts become reviewers of IPCC reports?
Experts are invited to register for the review through the website of the IPCC Working Group or Task Force responsible for the report.
Because the aim of the expert review is to get the widest possible participation and broadest possible expertise, those who register are accepted unless they fail to demonstrate any relevant qualification.
Sometimes the Working Group or Task Force Bureau concerned will also invite specific individuals to register to take part in the expert review, for instance if they have a particular area of expertise to contribute. This does not give them more legitimacy than any other expert reviewer.
The role of expert reviewers of IPCC reports
Expert reviewers may submit comments on one sentence or section of a report, or a whole chapter of the full report. They may consider scientific substance or the structure of the report. Often they will point out a published paper that the report authors may not have included in their assessment, but which could be relevant.
Expert reviewers agree not to cite, quote or distribute the draft, because at this stage the report is still a work in progress and has not yet been formally considered by the IPCC. They must submit their comments through the IPCC website.
Expert reviewers who submit comments are credited by name in the final report for their contribution. Such comments are a vital contribution to the quality of the assessment. But because the review is essentially open to all through a self-declaration of expertise, it follows that having been a registered expert reviewer does not by itself serve as a qualification of the expert or support their credibility in a different context.
more information on this topic, please see our Factsheet on the IPCC
 Principles Governing IPCC Work, paragraph 3