Greenwire: Carbon dioxide emissions are turning the world’s oceans more acidic, endangering coral reefs and fisheries, the science academies of 70 nations warned today in a joint statement. The effect could be irreversible for tens of thousands of years, the academies said. They urged countries attending U.N. climate negotiations in Bonn, Germany, this week to cut the world’s CO2 emissions at least 50 percent below 1990 levels by 2050, with additional cuts after that. Without such action, …