Agence France-Presse: A sharp slowdown in coral growth on Australia’s Great Barrier Reef since 1990 is a warning sign that precipitous changes in the world’s oceans may be imminent, scientists said Friday. Strong evidence points to the cause being a combination of warmer seas and higher acidity from increased levels of atmospheric carbon dioxide, Australian Institute of Marine Science researchers reported. “The data suggest that this severe and sudden decline in calcification is unprecedented in at …