Rare and Extreme Events

Extreme events are rare and their rareness poses various problems to quantitative statements about extremes. As the aspect of large impact implies, there is always some object that is exposed to an extreme event. All systems that exhibit extreme events are driven or open systems in permanent motion. This chapter discusses the general concept of extreme events and suggests that there might be some commonalities between the different phenomena that justify a more general point of view. It focuses on the issue of reproducibility, which is relevant for extreme events due to their rareness. The chapter then considers the role of the impact of an event onto a second system which is exposed to it. It argues that complex systems are often particularly vulnerable to extreme events, which, might have stronger impact on their evolution than the accumulated action of all smaller events.