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New research finds coral refugia, where reefs are protected from global warming by cool local currents, are disappearing faster than expected.

By Bob Berwyn, Inside Climate News

In the race to save at least some remnants of the world’s coral reefs, a new study shows only one thing really matters—capping global warming at 1.5 degrees Celsius.

Even at only that level of warming, more than 99 percent of areas previously seen as potentially safe havens for coral will disappear. Warming of 2 degrees C would wipe out all the “reef refugia” where corals might survive relentlessly warming oceans.

coral reef bleaching

The grim projections are made in research published today in the journal PLOS One using new climate models that more accurately show how interactions between different parts of the climate system, like winds, ocean currents, clouds and multiyear ocean temperature changes like El Niño, affect reefs.

As recently as 10 years ago, models tended to show uniform ocean warming, without details critical to understanding coral reef survival, said co-author Piers Forster, director of the Priestley Centre at the University of Leeds.

“The latest generation are better able to capture marine heatwaves,” which cause coral-killing bleaching, he said. Bleaching occurs when ocean water temperatures become too warm and cause corals to expel the algae living in their tissues, turning their color white. Bleaching is the main cause of coral reef die-offs.

“We know that our baths do not warm uniformly when you turn the hot tap on,” he said, but can burn a bather’s toes while other parts of their body are comfortable.

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