point of no return

He also knew that injecting the seawater was their only hope of keeping the chain reaction in unit 1 from reaching a point of no return, and that every minute counted.

How long before this point of no return?

Dr. Abram added that other critical systems may soon reach a point of no return, including the ice shelves that hold back parts of the Antarctic ice sheet.

"There are certain moments in politics or governance which are the moments of 'crossing the Rubicon' -- that point of no return," Saliya Pieris, former head of the Bar Association, wrote on Facebook.

The world's tropical coral reefs have almost certainly crossed a point of no return as oceans warm beyond a level most can survive, a major scientific report announced on Monday.