Preparing for high-impact, low-probability events: Lessons from Eyjafjallajökull

The frequency of ‘high-impact, low-probability’ (HILP) events in the last decade signals the emergence of a new ‘normal’. Apparent one-off high-profile crises such as 9/11, Hurricane Katrina, the Macondo oil spill and the Japanese earthquake and tsunami were all mega-disasters requiring rapid responses at a global level, marking the beginning of a crisis trend. But lower-profile, persistent events such as flooding, droughts and cyclones have been shown to have equally serious impacts, raising new questions about the way in which we perceive risk and prepare for disruptive events. These events can manifest themselves not only as ‘black swans’ – which by nature are impossible to predict – but also as known hazards such as floods, hurricanes or earthquakes, which, owing to the low likelihood of occurrence or the high cost of mitigating action, remain un- or under-prepared for. There are also crises such as pandemics which typically unfold over weeks, months or a few years, for which the scope or timing remains unknown even with preparations. Events such as the 2011 drought and subsequent food crisis in East Africa have also raised troubling questions about the way in which the international community responds to ‘slow-motion’ disasters which build up over several or many years.