The famous "doomsday clock" is a concept timepiece that first appeared in the Bulletin of the Atomic Scientists 60 years ago. Since then it has been an ongoing symbolic image that periodically changes to reflect new threats or treaties that influence the likelihood of nuclear holocaust.
This week, the clock was moved forward two minutes to stand at 5 minutes to midnight (aka "doomsday"). The move comes not because of new nuclear threats, but rather to reflect the risk of catastrophic global warming now faced by humankind. The announcement came during an unprecedented joint news conference at the American Association for the Advancement of Science in Washington, DC, and the Royal Society in London.