The ATLANTIS project, financially supported by the European Union’s DG Research, investigates the implications of a 5-6 metres sea level rise, due to a collapse of the West-Antarctic Ice Sheet, on the Rhone Delta, the Netherlands, and the Thames Estuary. This is one of the first studies to assess the societal consequences of impacts and adaptation to “imaginable worst case” climate change scenarios.

Because of the large uncertainties in the sea level rise scenario, and the even greater uncertainties in the social structure and land use in southeast France, the Netherlands and southwest England in the distant future, the project used only rough estimates of the changes in the natural system. We preferred to avoid developing precise models, as precision would be easily mistaken for accuracy, as any model would be used far outside its domain of calibration and validation. Instead, the project developed dense scenarios (storylines, or future histories) that are largely qualitative in nature, but do reflect, in an internally consistent manner, the complex implications of, say, having to abandon Marseille, Amsterdam or London. The project thus focused on what a 5-6 metre sea level rise would “mean” to people rather than on the “facts”. The scenarios were developed in a series of interviews and workshops with stakeholders.

In addition to the three case scenarios, a formal risk assessment was carried out, a social values and representations approach was enunciated, and the theory of optimal control under catastrophes was applied.