The Doomsday Clock, a symbolic measure of humanity's proximity to catastrophic destruction, has been set at 89 seconds to midnight—the closest it has ever been, symbolizing humanity's shortest margin from potential catastrophe since the clock's creation.

Scientists move the Doomsday Clock to 89 seconds before midnight, calling on the U.S., China and Russia to address global risks.

The Bulletin of Atomic Scientists announced Tuesday that the "Doomsday Clock" is now set to 89 seconds to midnight.