Great Barrier Reef corals just experienced hottest ocean temps in 400 years
Coral core samples can provide high-resolution data showing climate markers, including sea surface temperatures and sea level changes. This year proved to have the warmest ocean temperatures since the start of the Industrial Revolution.
Fourth global coral bleaching event underway
FILE VIDEO: NOAA scientists confirmed this week a global coral bleaching event is underway. NOAA Coral Reef Watch Coordinator Derek Manzello joins FOX Weather to talk about the global bleaching event and why coral reef habitats are important to ocean ecosystems.
Corals are among the best chroniclers of Earth's climate history, most recently helping scientists show that the 2024 sea surface temperatures experienced in the Great Barrier Reef were the warmest in at least 400 years.
In April, NOAA declared the fourth-ever global coral bleaching event was underway. Worldwide bleaching is happening because of historically high sea surface temperatures. Depending on the species of coral, 2-3 degrees above average ocean temperatures is all it takes for heat stress to begin to take its toll and begin bleaching.
A new study in the journal Nature used data from skeletal samples of corals taken starting in 1618 to determine past sea surface temperatures in the Coral Sea for Australia's warmest months: January, February, and March.
Corals seen on the Great Barrier Reef in the Coral Sea near Australia.
(Ove Hoegh-Guldberg)
"It's pretty amazing, really, because they've actually seen the entire industrial revolution in their life," said the study's lead author, Ben Henley, Ph.D. "They have actually lived through the start of the Industrial Revolution."
Henley, with the University of Melbourne, studies climate change through paleoclimate records, which include tree rings, coral records and ice cores.
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Corals make excellent timestamps for climate data because they lay down skeletons that grow 500 years or longer. According to a 2011 University of Queensland study, the Great Barrier Reef is built upon fossil reef structures that are hundreds of thousands of years old, with the living reef less than 10,000 years old.
Scientists drill for coral samples along the Great Barrier Reef in Australia.
When measured carefully in a laboratory, skeletal core samples can provide high-resolution time steps showing climate markers, including sea surface temperatures and sea level changes.
Henley's study had been ongoing for years before the 2024 bleaching event in the Great Barrier Reef. On a whim, Henley asked the study editor if he should include 2024 as a data point. The result was shocking.
"Lo and behold, it was actually plotted above any other January to March period in the whole 400 years," Henley said. "Of course, that's a result that I was shocked at and, needed to check many times just to make absolutely certain that it was. But it really is the warmest in the last 400, according to our analysis."
Sea surface temperature anomalies ranked from the 1600s to 2024. The year's with labels include the six warmest on record, including five mass coral bleaching events on the Great Barrier Reef.
Using climate models, the study authors confirmed that climate change was responsible for the long-term warming and the current bleaching event.
The study was published more than a week after the UN Educational, Scientific and Cultural Organization (UNESCO) World Heritage Committee declined to list the Great Barrier Reef as in danger.
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Henley hopes this study, showing that sea surface temperatures are the warmest in 400 years, could help UNESCO in its next assessment of the Great Barrier Reef.
"What we know about global warming, climate change, is the very clear identification of climate change as being responsible for the warming events that are then very directly tied to the bleaching events that we see on the reef," Henley said. "You put all of that evidence together, and I don't know many people who wouldn't say that the Great Barrier Reef is in danger."
Corals seen on the Great Barrier Reef in the Coral Sea near Australia.
(Ove Hoegh-Guldberg)
Located off the coast of Queensland, the Great Barrier Reef is the largest reef system on Earth, with 2,500 individual reefs. It's the ecological crown jewel of Australia, bringing in $6.4 billion each year to the economy and is responsible for about 64,000 jobs, according to the Great Barrier Reef Marine Park Authority.
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Henley believes ecotourism is tied to helping the reef survive climate change.
"I actually just think the more people that love and care about the reef the better," Henley said. "And the more people that visit it, and there's a higher chance that they care about the reef and protect it."
As part of the World Heritage Committee decision, Australia must submit a progress report on the Great Barrier Reef by February 2025.