The “doomsday clock” symbolising how close humanity is to destruction ticked one second closer to midnight Tuesday as concerns on nuclear war, climate and public health were jolted by US President Donald Trump’s return.

The Doomsday Clock now stands at 89 seconds to midnight, the closest to catastrophe in its nearly eight-decade history. Here's a look at how — and why — it's moved.

The Doomsday Clock indicates only 89 seconds to midnight, according to which we have never been so close to self-destruction. The Doomsday Clock, developed by physicists after World War II, symbolizes humanity's nearness to total annihilation.

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.

The Bulletin of the Atomic Scientists cited climate change, instability in the Middle East and the threat of pandemics as reasons the Earth is closer than ever to total destruction.