Textual analysis of the WGI contribution to the AR6: Review of the use of uncertainty language and scenarios in the report chapters, ES, TS & SPM

The aim of this study is to quantify and qualify the use of uncertainty language and different evolution scenarios in the WGI contribution to the AR6, Climate Change 2021: The Physical Science Basis.

The uncertainty language corresponds to the use of calibrated IPCC language to describe the probability, agreement, quantity and quality of evidence, and the degree of confidence in the assertions. The scenarios studied are the RCPs (Representative Concentration Pathway) and SSPs (Shared Socioeconomic Pathways).

The use of these different terms has been discussed in the report chapters as well as in the Executive Summaries (ES), the Technical Summary (TS) and the Summary for Policy Maker (SPM).

For each of the terms (uncertainty language or evolution scenario), a quantitative study shows the number of terms used within the chapters. A standardized version is sometimes presented to qualify the influence of the length of the chapters. A qualitative study then compares the distribution of terms across the chapters and tries to explain the observations. A similar study is then conducted to compare the full report with the TS and the SPM.

The terms searched in the report were only in lower case (e.g. "very likely" and not "Very likely") in order to count only occurrences within sentences and to limit the contribution of terms in table headings for example.