We publish the definition of "Confidence", "Likelihood" and "Uncertainty" as a service to our loyal readers. – Ed.
The latest report from the IPCC
which analyzes data on climate change states "extreme confidence" that human activity is responsible for global warming, yet skeptics continue to disagree. So what does "extreme confidence" mean exactly, and is the language used by the IPCC unequivocal
in describing its findings?
(From the Intergovernmental Panel on Climate Change Glossary of Terms
The level of confidence in the correctness of a result is expressed in this report, using a standard terminology defined as follows:
Terminology Degree of confidence in being correct
confidence At least 9 out of 10 chance of being correct
About 8 out of 10 chance
About 5 out of 10 chance
About 2 out of 10 chance
Very low confidence
Less than 1 out of 10 chance
See also Likelihood; Uncertainty.
The likelihood of an occurrence, an outcome or a result, where this can be estimated probabilistically, is expressed in IPCC reports using a standard terminology defined as follows: Terminology Likelihood of the occurrence / outcome
>99% probability of occurrence
More likely than not
About as likely as not
33 to 66% probability
<1% probability See also Confidence; Uncertainty.
An expression of the degree to which a value (e.g., the future state of the climate system) is unknown. Uncertainty can result from lack of information or from disagreement about what is known or even knowable. It may have many types of sources, from quantifiable errors in the data to ambiguously defined concepts or terminology, or uncertain projections of human behavior. Uncertainty can therefore be represented by quantitative measures, for example, a range of values calculated by various models, or by qualitative statements, for example, reflecting the judgement of a team of experts (see Moss and Schneider, 2000; Manning et al., 2004).
See also Likelihood; Confidence.
Read more about this story on Blue Boat, and find a link to the IPCC report