Until now, the ocean has been the hero of the climate crisis—about 90 percent of the additional heat we’ve trapped from burning fossil fuels has been absorbed by it. “Without the ocean, the atmosphere would be a lot hotter than it already is,” Ken Caldeira, a senior climate scientist with Breakthrough Energy in California, told me. But the heat the ocean absorbed has not magically vanished—it’s just stored in the depths and radiated out later.
