The Doomsday Clock is a symbolic clock face, representing a countdown to possible global catastrophe (e.g. nuclear war or climate change). It has been maintained since 1947 by the members of the Science and Security Board of the Bulletin of the Atomic Scientists, who are in turn advised by the Governing Board and the Board of Sponsors, including 18 Nobel Laureates. The closer they set the Clock to midnight, the closer the scientists believe the world is to global disaster.
Originally, the Clock, which hangs on a wall in the Bulletin's office in the University of Chicago, represented an analogy for the threat of global nuclear war; however, since 2007 it has also reflected climate change and new developments in the life sciences and technology that could inflict irrevocable harm to humanity. The most recent officially announced setting—three minutes to midnight (23:57)—was made in January 2015 due to "[un]checked climate change, global nuclear weapons modernizations, and outsized nuclear weapons arsenals".This setting was retained in January 2016.