The IPCC should adjust the way it communicates scientific uncertainty about climate change and reform its management structure, according to an international report presented overnight to UN Secretary-General Ban Ki-moon and IPCC chair Rajendra Pachauri.
The report notes that, in the most recent assessment report, each of the three IPCC working groups talked about scientific uncertainty in different ways (see electronic page 5 of the latest IPCC synthesis report for an outline).
The review report by the InterAcademy Council reserves particular criticism for the summary for policy-makers of IPCC Working Group II on impacts, adaptation and vulnerability, which attempted to deal with uncertainty mainly by attributing levels of confidence to statements.
In fact, it ended up attributing 'high confidence' to some statements "for which there was little evidence", the review report says.
"Furthermore, by making vague statements that were difficult to refute, authors were able to attach 'high confidence' to the statements."
The Working Group II summary for policy-makers contains many such statements that are "not supported sufficiently in the literature, not put into perspective, or not expressed clearly", it says.
The review recommends that all IPCC reports use a "level of understanding scale" which describes the amount of evidence available and the degree of agreement among experts (for example, 'high agreement, much evidence' or 'medium agreement, medium evidence').
It also recommends using a "likelihood scale" when statements about events are well defined and supported by evidence indicating when and under what climate conditions they would occur.
This type of scale was used extensively in the latest IPCC working group I report, which talks about events as being "extremely likely" (greater than 95% probability), "very likely" (greater than 90%), "likely" (greater than 66%), down to exceptionally unlikely (less than 1%).
Establish an IPCC executive committee
Under the existing IPCC process, representatives of 194 participating governments agree on the scope of each assessment, elect the scientific leaders for it, nominate authors, review the results and approve the summaries written for policy makers.
More than a thousand volunteer scientists evaluate the available scientific, technological, and socioeconomic information on climate change, and draft and review the assessment reports.
The review report says these scientists and government representatives "are the major strength of the organisation" and the process "has been successful overall".
"However, the world has changed considerably since the creation of the IPCC, with major advances in climate science, heated controversy on some climate-related issues, and an increased focus of governments on the impacts and potential responses to changing climate," it says.
The report recommends that the IPCC establish an executive committee to act on its behalf between its meetings. The committee should comprise the IPCC chair, the co-chairs of its working groups, the head of its secretariat "and three independent members, including some from outside the climate community".
It also recommends that the secretariat be headed by an executive director, elected by the IPCC, who should be a senior scientist and whose tenure would last only for the term of a single IPCC assessment report.
Ban Ki-moon and Pachauri jointly requested the review in March.
