The confidence levels and likelihood statements used in this report are the same as those used in the IPCC Fifth Assessment Report (IPCC, 2013). Generally, evidence is most robust when there are multiple, consistent independent lines of high-quality evidence. A level of confidence is expressed using five qualifiers: very high, high, medium, low, and very low. The figure depicts summary statements about evidence and agreement and their relationship to the confidence scale. The relationship is flexible, with “fuzzy boundaries” between difference confidence levels. The categories of likelihood are also considered to have fuzzy boundaries. For example, a statement that a result is likely means that the probability of its occurrence ranges from over 66% to 100%. This corresponds to a chance of the event occurring of two-thirds or more.
Mastrandrea et al., 2010.