Coral reefs are early casualties of climate change, but not every coral reacts the same way to the stress of ocean warming. Researchers have developed the first-ever quantitative ‘global index’ detailing which of the world’s coral species are most susceptible to coral bleaching and most likely to die. Based on historical data, the index can be used to compare the bleaching responses of the world’s corals and to predict which corals may be most affected by future bleaching events.