The Doomsday Clock is now at 89 seconds to midnight. Sky News looks at the meaning behind it, what it is and how it works.

In what may not come as much of a shock to many, the Doomsday Clock has inched closer to midnight and is now 89 seconds away from the ominous hour. It's the closest the two hands have ever been to the symbolic 12 on the clock face in its 80 years.

"This is a bleak picture. But it is not yet irreversible."

Scientists and global leaders revealed on Tuesday that the "Doomsday Clock" has been reset to the closest humanity has ever come to self-annihilation.