In 1964, "experts" were saying that the Great Barrier Reef was dying. Cause: DDT and other pesticides.

Later on, "experts" said the Reef was dying because of air polution and Acid Rain.

In the late 1970s, it was Global Cooling (aka coming of a new Ice Age) that would kill the Great Reef.

Now the "scientists" predict its demise from Global Warming.

Actually, Austrailia's Great Barrier Reef is just fine. It does have some dead spots, mostly caused by old age. Overall, it is in just about the same shape as it was before Europeans arrived. Go swimming and enjoy.