Baum and Barrett (2018) gesture at some additional definitions/​conceptualisations of global catastrophic risk that have apparently been used by other authors:
In general terms, a global catastrophe is generally understood to be a major harm to global human civilization. Some studies have focused on catastrophes resulting in human extinction, including early discussions of nuclear winter (Sagan 1983). Several studies posit minimum damage thresholds such as the death of 10% of the human population (Cotton-Barratt et al. 2016), the death of 25% of the human population (Atkinson 1999), or 104 to 107 deaths or $109 to $1012 in damages (Bostrom and Ćirković 2008). Other studies define global catastrophe as an event that exceeds the resilience of global human civilization, resulting in its collapse (Maher and Baum 2013; Baum and Handoh 2014).
Baum and Barrett (2018) gesture at some additional definitions/​conceptualisations of global catastrophic risk that have apparently been used by other authors: