On the boundaries of probabilistic risk assessment in the face of uncertainties, a case of piracy and armed robberies against ships in the Gulf of Aden

It is a common conception among many researchers and analysts, in particular social scientists, that using probabilistic risk assessment (PRA) when there are large uncertainties about likelihoods and outcomes is irrational, unscientific and potentially misleading. In this paper, we look more closely into this issue: the boundaries of PRAs when there are large uncertainties about the phenomena and processes analysed. Using an example of maritime piracy, we demonstrate that PRA also has an important role to play in risk management when the uncertainties are large. A paradigm shift is, however, required for how to conduct and use the risk assessments. The ambition of precise risk estimation has to be replaced by uncertainty assessments and characterisation.