Hottest ocean temperatures in 400 years an ‘existential threat’ to the Great Barrier Reef, researchers find

White coral at the Great Barrier Reef in 2024 after a mass bleaching event, one of many in recent years. Photograph: Ove Hoegh-Guldberg

Ocean temperatures in the Great Barrier Reef are now the hottest in at least 400 years and are an “existential threat” to the planet’s unique natural wonder, according to new scientific research.

Scientists analysed long-lived corals in and around the reef that keep a record of temperature hidden in their skeleton and matched them to modern observations.