WASHINGTON (AFP) – Some 80 percent of Arctic ice may disappear in 30 years, not 90 as scientists had previously estimated, according to a new study on the impact of global warming. "The amount of the Arctic Ocean covered by ice at the end of summer by then could be only about 1 million square kilometers, or about 620,000 square miles," said US researchers who authored the study published Thursday. "That's compared to today's ice extent of 4.6 million square kilometers, or 2.8 million square miles," they added, warning the development "raises the question of ecosystem upheaval." The scientists made...