Handling uncertainty about climate change
Via Understanding Uncertainty
The guidance follows the work of Risbey and Kandlikar in recommending that the precision of any statement about an unknown quantity should depend on the quality of the available evidence, and that numerical probability statements should only be made about well-defined events and when there is ‘high agreement, much evidence’. They distinguish between ‘likelihood’ defined as a ‘probabilistic assessment of some well defined outcome having occurred or occurring in the future’, and ‘levels of confidence’ ‘based on expert judgement as to the correctness of a model, an analysis or a statement’. Tables 2 and 3 provide a mapping between linguistic terms and numerical values for likelihood and confidence .
…..“.. very high confidence that the global average net effect of human activities since 1750 has been one of warming” and “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”.