The Doomsday Clock
is a symbol that represents the likelihood of a human-made global catastrophe, in the opinion of the members of the Bulletin of the Atomic Scientists
. Maintained since 1947, the clock is a metaphor for threats to humanity from unchecked scientific and technological advances. A hypothetical global catastrophe is represented by midnight on the clock, with the Bulletin'
s opinion on how close the world is to one represented by a certain number of minutes or seconds to midnight, assessed in January of each year. The main factors influencing the clock are nuclear risk and climate change. The Bulletin'
s Science and Security Board monitors new developments in the life sciences and technology that could inflict irrevocable harm to humanity.