by Alan Jones, interviews peter Ridd, July 28, 2017 in JoNova
Corals have a little thermometer built in them, when you take a core of them from many years ago we know what the temperature of the water was back when Captain Cook sailed up the coast, it was actually about the same temperature then. It was colder 100 years ago, but it has recovered from that. The temperatures on the reef are not even significantly warmer than average on a hundred year timescale.
Corals that bleach in one year will be less susceptible to bleaching in following years