Meteorite could have triggered past episode of climate change

Telegraph : A period of significant global cooling called the Younger Dryas , which occurred between 12 800 and 11 500 years ago may have been caused by a meteorite explosion and impact. James Wittke of Northern Arizona University and his colleagues examined carbon spherules from 18 archeological sites worldwide, dating to 12 800 years ago. They found that the spherules were formed by sediments melting at temperatures of 2200 °C. They compared them with similar spherules from volcanoes, lightning, and human sources and determined that the ones they found were caused by heat and shock waves from an object passing through and exploding in the atmosphere. They estimate that 10 million tons of the spherules were spread over an area of 49 million km ² as a result of the meteorite fragmentation. The dust and ash could have triggered the significant cooling that followed and that was partly responsible for the extinction of several species, including woolly mammoths, and for major changes in human behaviors.