From scenario definition to uncertainty analysis communication with the risk managers

2 From scenario definition to uncertainty analysis communication with the risk managers 

The calculated exposure results are expressed in the language of numbers. The level of uncertainty is described qualitatively or quantitatively. A numerical approach has the advantages of precision, leaving less room for misinterpretation and providing more input for the decision-maker (Covello Merkhofer, 1993). 

Take away variety and nothing remains but averages with zero standard deviations and central tendencies always on the mark. Take away variety, in other words, and we eliminate uncertainty. .. But the sum and substance of risk management is in the recognition of variety. [Bernstein, 1996] 

Using default values, the selected range of the influencing variables must be chosen well, as the complaint of any particular person that You have not considered that for me/my family the exposure (this influence factor) is higher than the one that you have used might devalue the whole exposure assessment in a public debate. Furthermore, in the authors experience, it is much better to use distributions for the influence factors. Considering combinations of distributions for the input variables might lead to answers like We have considered 

We must act on facts, and on the most accurate interpretation of them, using the best scientific information. .. That does not mean that we must sit back until we have 100% evidence about everything. Where the state of the health of the people is at stake, the risks can be so high and the costs of corrective action so great, that prevention is better than cure. We must analyse the possible benefits and costs of action and inaction. 

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