Doomsday Clock stays unchanged at three minutes to midnight

The Iran nuclear deal and movement on climate change prompted the scientists who maintain the Doomsday Clock, a symbolic countdown to global catastrophe, to keep it unchanged on Tuesday at three minutes to midnight. The Doomsday Clock, devised by the Chicago-based Bulletin of the Atomic Scientists, is widely recognised as an indicator of the world's vulnerability to catastrophe. The Doomsday Clock's hands "are the closest they've been to catastrophe since the early days of above-ground hydrogen