Table 1: IPCC guidelines for translation of probability phrases.

From: The interpretation of IPCC probabilistic statements around the world

PhraseLikelihood
Virtually certain>99%
Very likely>90%
Likely>66%
About as likely as not33%–66%
Unlikely<33%
Very unlikely<10%
Exceptionally unlikely<1%
  1. Note: In some IPCC reports authors have used the phrases ‘More likely than not’ for probabilities > 50%, ‘Extremely likely’ for probabilities above 95% and ‘Extremely unlikely’ for probabilities below 5%.