Extreme events defined-A conceptual discussion applying a complex systems approach

'Extreme event', a term today most commonly understood and used in relation to extreme weather phenomena and experiencing an upsurge in its usage due to their increased frequency caused by climate change, is applied in a variety of scientific disciplines. Its multitude of users understands and defines the term differently. However, consistency in language is vital to eradicate confusion, support the transfer of knowledge from one field to another, and make results from different disciplines comparable. Therefore, this work gives an in-depth discussion of the various aspects of relevance, ultimately proposing a comprehensive, systems-based definition of the term. Novel to this definition is the complex systems approach, utilized throughout to allow the definition to be applied for both macrolevel and microlevel occurrences and across various disciplines. In contrast to most authors who separate incident and impacts and use either the former or the latter in definitions of extreme events, it is shown that a disruption to a system or systems is prerequisite. Only by applying this perspective can interdisciplinary research be successfully conducted on extreme events. This and other central aspects come particularly to light in a case study of the 2006 European Blackout, on which the meta-definition is tried.