Threat to civilization, humans and the Earth - the threat to the existence of which can completely destroy mankind, have adverse consequences for the development of human civilization, or even destroy the planet Earth.  This idea is usually expressed by such phrases as "global catastrophe", "End of the World", "Doomsday", "Armageddon" and other events in the next point - catastrophic scenarios - different from other types of hazards (such as earthquakes), both in scale, so and gravity.
While some natural disasters, such as supervolcanoes and asteroids can destroy humanity if they are powerful enough, as well as man-made catastrophic events, or global warming, nuclear war or bioterrorism. 
The apocalyptic scenario is difficult to study in spite of the importance of global risks. Although individual threats, such as nuclear war or climate change, have been studied intensively since 2002. 

There are various threats to human existence, but not all of them are equally dangerous. Threats can be roughly divided into six types, based on the magnitude of these threats (personal, regional, global) and their intensity (portable and deadly). The table to the right shows some examples.
Threats discussed in this article are not "almost imperceptible", "local" or "private." Hamays Cassio (born Jamais Cascio) has created an alternative classification system