Glossary

In the IPCC’s Fifth Assessment Report (AR5), a standard term, defined in the introduction, is used to describe the level of confidence in a given statement. In order to accurately reflect scientific uncertainty, the statements made (in all parts of the Report) are rated by the team of authors, either qualitatively (“very low” to “very high” confidence) or – if possible – using quantitative probabilities. These range from “virtually certain” (99–100% probability) and “extremely likely” (90–100% probability) to “likely” (66–100% probability), all the way to “extremely unlikely” (0–1% probability). Where applicable, statements are also presented as facts (without any reference to probability).