Abstract
The uncertainty language framework used by the Intergovernmental Panel on Climate Change (IPCC) is designed to encourage the consistent characterization and communication of uncertainty between chapters, working groups, and reports. However, the framework has not been updated since 2010, despite criticism that it was applied inconsistently in the Fifth Assessment Report (AR5) and that the distinctions between the framework’s three language scales remain unclear. This article presents a mixed-methods analysis of the application and underlying interpretation of the uncertainty language framework by IPCC authors in the three special reports published since AR5. First, I present an analysis of uncertainty language term usage in three recent special reports: Global Warming of 1.5°C (SR15), Climate Change and Land (SRCCL), and The Ocean and Cryosphere in a Changing Climate (SROCC). The language usage analysis highlights how many of the trends identified in previous reports—like the significant increase in the use of confidence terms—have carried forward into the special reports. These observed trends, along with ongoing debates in the literature on how to interpret the framework’s three language scales, inform an analysis of IPCC author experiences interpreting and implementing the framework. This discussion is informed by interviews with IPCC authors. Lastly, I propose several recommendations for clarifying the IPCC uncertainty language framework to address persistent sources of confusion highlighted by the authors.
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Notes
For a more detailed discussion of Aven’s (2019) interpretation of the confidence and likelihood scales, see the Supplementary Material.
Source: interviews with members of the IPCC Bureau.
The analysis preceded the publication of the final drafts of the SRCCL and SROCC and is based on the “approved drafts,” which were subject to final edits and tricklebacks. Trickleback documents for the SRCCL and SROCC contain only 25–30 suggested revisions associated with uncertainty language each. Therefore, the term usage in the final drafts may vary slightly from the data used in this analysis but will not significantly affect the findings presented here.
The IPCC author database does not provide information on author participation in the FAR, SAR, or TAR.
Interviews by chapter/group: SRCCL Ch. 4 (4); SRCCL Ch. 6 (2); SROCC Ch. 2 (3); SROCC Ch. 5 (3); IPCC Bureau (2). Interview requests were sent to all CLAs and LAs for each chapter and were conducted with all individuals that responded.
A series of final revisions of report chapters following the SPM approval meetings.
A sentiment that is not echoed by many risk/uncertainty scientists (Aven 2019).
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Janzwood, S. Confident, likely, or both? The implementation of the uncertainty language framework in IPCC special reports. Climatic Change 162, 1655–1675 (2020). https://doi.org/10.1007/s10584-020-02746-x
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DOI: https://doi.org/10.1007/s10584-020-02746-x