A study published on Tuesday showed that more than half of the world's coral reefs were bleached between 2014-2017 -- a record-setting episode now being eclipsed by another series of devastating heatwaves.

The two previous global bleaching events, in 1998 and 2010, had lasted one year.

“2014–17 was the first record of a global coral bleaching event lasting much beyond a single year,” the study said.