In a sea of grim stories about the health and fate of the Great Barrier Reef comes one of the grimmest: "Highest ocean heat in four centuries places Great Barrier Reef in danger." That's the title of a study published Tuesday in Nature. Researchers say they reconstructed 400 years of summer sea surface temperatures in the Coral Sea and found the January to March heat extremes were the highest ever in 2024, with the next highest occurring (in descending order) in 2017, 2020, 2016, 2004, and 2022, per a press release. The Guardian reports 2024's temperature was 1.73 degrees Celsius above the 1618–1899 average.
"When I plotted the 2024 data point, I had to triple check my calculations—it was off the charts—far above the previous record high in 2017. I could almost not believe it. Tragically, mass coral bleaching has occurred yet again this year," said study author and University of Melbourne Lecturer Dr. Benjamin Henley, who warned bleaching could begin to occur near annually unless protective measures are taken. Indeed, the press release explains five of those six hottest years correlate with mass bleaching events. His prediction is dour: "In the absence of rapid, coordinated, and ambitious global action to combat climate change, we will likely witness the demise of one of Earth's most spectacular natural wonders."
To that end, the researchers implore UNESCO's World Heritage Committee to take their study into account and reconsider its decision, made two weeks ago, to decline to list the Great Barrier Reef as "in danger." The Guardian reports the committee is set to next consider the reef's classification in 2026. The New York Times notes the study comes during the most expansive bleaching event on record: From January 2023 to this August, 74% of the reef area in our oceans has been subjected to bleaching-level heat stress, per the National Oceanic and Atmospheric Administration's Coral Reef Watch. That outpaces the 65.7% recorded between 2014 and 2017. (More Great Barrier Reef stories.)