What is the Doomsday Clock? It's 2025 and scientists have reset the clock closer to midnight and global catastrophe. Here's what it all means.

Artificial intelligence was not listed as a chief concern two years ago, the last time the Bulletin of the Atomic Scientists moved the clock closer to global catastrophe.

The Doomsday Clock now stands at 89 seconds to midnight reflecting unprecedented global risks including nuclear proliferation and climate change.