Coral reefs are already under stress due to increasing numbers of "bleaching events." When ocean temperatures rise for weeks or more, coral, which are actually tiny marine animals, expel the algae that live within them. These symbiotic algae provide the coral with a major source of food. If water temperatures drop the coral can recover, but are weakened. Too many bleaching events can kill them.
With overfishing, coastal development and the pollution it brings, bleaching and ocean acidification, the world's coral reefs are undergoing enormous changes, says NOAA's Billy Causey. "Coral will survive, but will it be in the forms we know?" he says.
One hope is that the worst-case global warming scenarios don't have to go that way, says study co-author, Ken Caldeira, a professor of global ecology at the Carnegie Institution.
"It's a much easier problem to handle than say Hitler," he said. "We came into WWII with biplanes and came out of it with jet planes and integrated circuits. If our society actually perceived this as a threat, we could fairly easily mobilize and respond to it."