Have the world’s coral reefs already crossed a tipping point?

About a year ago, the seas got unusually hot, even by our current, overheated standards. Twelve months of broken records later, the oceans are still more feverish than climate models and normal fluctuations in global weather patterns can explain.

When the seas turn into bathwater, it threatens the survival of the planet’s coral reefs, home to a quarter of all marine life and a source of sustenance for many people living along the world’s coasts. Mostly clustered in the shallow waters of the tropics...