Table 1 IPCC guidelines for translation of probability phrases.

From: The interpretation of IPCC probabilistic statements around the world

Phrase Likelihood
Virtually certain >99%
Very likely >90%
Likely >66%
About as likely as not 33%–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%.