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Multiple comet impacts around 1500 years ago triggered a "dry fog" that plunged half the world into famine. Historical records tell us that from the beginning of March 536 AD, a fog of dust blanketed the atmosphere for 18 months. During this time, "the sun gave no more light than the moon", global temperatures plummeted and crops failed, says Dallas Abbott of Columbia University's Lamont-Doherty Earth Observatory in New York... Now Abbott and her team have found the first direct evidence that multiple impacts caused the haze. They found tiny balls of condensed rock vapour or "spherules" in debris inside...

Double impact may have caused tsunami, global cooling Pieces of a giant asteroid or comet that broke apart over Earth may have crashed off Australia about 1,500 years ago, says a scientist who has found evidence of the possible impact craters. Satellite measurements of the Gulf of Carpentaria (see map) revealed tiny changes in sea level that are signs of impact craters on the seabed below, according to new research by marine geophysicist Dallas Abbott. Based on the satellite data, one crater should be about 11 miles (18 kilometers) wide, while the other should be 7.4 miles (12 kilometers) wide....