thesisTraditionally, stratospheric sudden warming events (SSWs) are defined using a fixed threshold criterion. This criterion, however, may lead to spurious results if the climate of the underlying dataset is changing. In an attempt to overcome this potential shortcoming we develop alternative criteria to define such events and test these criteria using reanalysis and climate model data. Results show that under different future climate forcing scenarios the annual and monthly mean SSW frequency increase. This increase is most robust in early to mid-winter. We therefore conclude that under a changing climate there is a higher potential for winter cold air outbreaks for regions such as North America, Europe, and northern Asia
