Since 1947 the magazine " Bulletin of the Atomic Scientists" has given reports on the state of the world in regards to the global level of nuclear danger. To symbolize the threat, a clock is used, which indicates how urgent the threat is. Midnight is seen as the ultimative acopalyptic time.
The current time to midnight is available under:
http://www.thebulletin.org/doomsday_clock/current_time.htm
You may be also interested in an older article by the anthropologist Hugh Gusterson and his article for the 50th Anniversary of the Bombing of Hiroshima in 1995.
http://web.mit.edu/anthropology/faculty_staff/gusterson/op-eds/On_the_Anniversary_of_Hiroshima_Lmore_Indept.html