For the past decade, water temperatures along Australia's famed Great Barrier Reef have been the warmest in 400 years. That's according to a major study in the science journal Nature, with the co-author Helen McGregor telling AFP that the heating recorded is “unprecedented”. Ocean temperatures around the iconic coral system have increased yearly since 1960 but were particularly hotter during recent mass coral bleaching events, the study says. IMAGES AND SOUNDBITES