Great Barrier Reef waters were hottest in 400 years over the past decade

SYDNEY (AP) — Ocean temperatures in the Great Barrier Reef hit their highest level in 400 years over the past decade, according to researchers who warned that the reef likely won’t survive if planetary warming isn’t stopped.

During that time, between 2016 and 2024, the Great Barrier Reef, the world’s largest coral reef ecosystem and one of the most biodiverse, suffered mass coral bleaching events. That’s when water temperatures get too hot and coral expel the algae that provide them with color and food, and sometimes die. Earlier this year, aerial surveys of over 300 reefs in the system off Australia’s northeast coast found bleaching in shallow water areas spanning two-thirds of the reef, according to NASA.

Researchers from Melbourne University and other universities in Australia, in a paper published Wednesday in the journal Nature, were able to compare recent ocean temperatures to historical ones by using coral skeleton samples from the Coral Sea to reconstruct sea surface temperature data from 1618 to 1995. They coupled that with sea surface temperature data from 1900 to 2024.