Uncertainties and risks have always been, and will remain, present; both in everybody’s life and in policy making. This presence is not always recognized because humans tend to perceive the world in a deterministic way, and in most cases succeed in somehow dealing with uncertainties. However, ignoring uncertainties often results in serious problems that could at least be mitigated if the uncertainties were properly handled. The importance of the proper treatment of uncertainties is growing because the consequences of inadequate treatments are more and more costly, both in social and environmental terms. This is caused by the quickly changing world where one of the dominating driving forces is efficiency, which has led to globalization, increased interdependencies amongst more and more diversified socio-economic, technological and environmental systems, a reduction in many safety (both technological and social) margins, a concentration of assets in risk prone areas, and other factors which progressively contribute to the increasing vulnerability of the societies.
These ongoing global changes create fundamentally new scientific problems which require new concepts, methods, and tools. A key issue concerns a vast variety of practically irreducible uncertainties, which challenge our traditional models and require new concepts and analytical tools. This uncertainty critically dominates a number of policy making issues, e.g., the climate change debates. In short, the dilemma is concerned with enormous costs vs massive uncertainties of potentially extreme and/or irreversible impacts.