The Doomsday Clock is a symbol which represents the likelihood of a human-caused global catastrophe. Maintained since 1947 by the members of The Bulletin of the Atomic Scientists'Science and Security Board, the Clock, which hangs on a wall in The Bulletin's office in the University of Chicago, represents an analogy for the threat of global nuclear war. 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 Clock represents the hypothetical global catastrophe as "midnight" and The Bulletin's opinion on how close the world is to a global catastrophe as a number of "minutes" to midnight. Its original setting in 1947 was seven minutes to midnight. It has been set backward and forward 22 times since then, the smallest ever number of minutes to midnight being two (in 1953) and the largest seventeen (in 1991). As of January 2017, the Clock is set at two and a half minutes to midnight, due to a "rise of 'strident nationalism' worldwide, United States President Donald Trump's comments over North Korea, Russia, nuclear weapons, and the disbelief in the scientific consensus over climate change by the Trump Administration."