Temperatures in Great Barrier Reef reach 400 year high, scientists reveal

Scientists have revealed co-ordinated action must be taken to save the Great Barrier Reef after water temperatures reach unprecedented levels.

Alarming new research has revealed the Great Barrier Reef will inevitably succumb to the impacts of climate change as temperatures in surrounding waters reach a 400-year high.

Leading climate scientists found sea surface temperatures in the Coral Sea surrounding the reef in the January to March period of 2017 and 2020 were the warmest on record for four centuries.

But in 2024, temperatures in the same period reached “unprecedented” levels.

Scientists have revealed temperatures in the Great Barrier Reef have reached unprecedented levels. Picture: Tane Sinclair-Taylor

University of Melbourne lecturer and lead researcher Benjamin Henley said he had to “triple check” his calculations when he saw the results.

“It was off the charts – far above the previous record high in 2017. I could almost not believe it.” he said.

The study used the chemistry of the corals in the Coral Sea to reconstruct ocean temperatures between 1618 and 1995 and combined it with instrument measurements taken from 1900 to 2024.

Using the data, the researchers were able to rank four centuries of summer sea surface temperatures with “greater precision” than ever before.

Dr Henley said mass coral bleaching had “tragically” occurred once again this year as a result of rising sea temperatures.

A mass coral bleaching event in the reef occurred in 2024. Picture: Ove Hoegh-Guldberg

Coral bleaching occurs when the reef’s waters stay too hot for too long and coral become stressed and subsequently expel the algae responsible for allowing them to grow and reproduce.

What was once vibrant and colourful coral then becomes white and the coral’s skeleton is exposed.

The mass coral bleaching event that occurred in 2024 is the fifth to occur since 2016.

The research also found human influence is a driving force behind the warming and Dr Henley said action must be taken to protect the coral reef.

“In the absence of rapid, co-ordinated and ambitious global action to combat climate change, we will likely witness the demise of one of Earth’s most spectacular natural wonders,” he said.

Coral bleaching is caused by prolonged periods of warm ocean water. Picture: Ove Hoegh-Guldberg

“When you compile all of the evidence we have, it’s the inevitability of the impacts on the reef in the coming years that really gets to me.”

University of Wollongong honorary fellow and the study’s second author Helen McGregor said The Great Barrier Reef is “facing catastrophe” if anthropogenic climate change is not immediately addressed.

“The very corals that have lived for hundreds of years and that gave us the data for our study are themselves under serious threat,” she said.

“Our climate model analysis confirms that human influence on the climate system is responsible for the rapid warming in recent decades.”

The research comes more than a week after UNESCO’s World Heritage Committee decided not to list the World Heritage-listed site as “in danger” despite extensive lobbying by the Australian government.