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Studies Refute Hypothesis on What Caused Abrupt Climate Change Thousands of Years Ago

posted by on Wednesday January 04 2017, @03:01AM   Printer-friendly
from the no-smoking-bolide dept.

Arthur T Knackerbracket has found the following story:

Two new studies in the Journal of Quaternary Science refute the hypothesis that one or more comets/bolides struck North America approximately 12,900 years ago triggering rapid climate change and the start of the Younger Dryas period.

Prior to the Younger Dryas, the climate had gradually warmed from glacial conditions to near modern temperatures, and the massive ice sheets in North America were in full retreat; however, approximately 12,900 years ago, temperatures rapidly plummeted and returned to glacial conditions for about a 1200 year long period. Also about this time, the mammoths and mastodons became extinct in North America.

The two papers challenge two lines of evidence reported and used by others to support the impact theory. One is the report of elevated concentrations of nanometer-sized diamonds in sediments deposited at the onset of the Younger Dryas. It is claimed that these diamonds were formed during an impact. The other is the interpretation that paleofire evidence at a key archaeological site demonstrates massive wildfires at the beginning of the Younger Dryas. It is claimed that the impact caused wildfires that spanned the continent.

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  • (Score: 3, Informative) by Anonymous Coward on Wednesday January 04 2017, @07:31AM

    by Anonymous Coward on Wednesday January 04 2017, @07:31AM (#449267)
    The Younger Dryas were a period of abrupt climate change that began 12,900 years ago and lasted for about a thousand years, when the warming temperatures after the last glacial maximum suddenly reversed course. Temperatures in Greenland fell to 15°C below what they are today, retreating glaciers began to advance again, regions of the world were afflicted with drought. It’s said to be caused by the shutdown of the North Atlantic thermohaline circulation (cf. The Day After Tomorrow), although what caused that to happen is still unclear. One hypothesis was that it was caused by a cometary or asteroid impact, but the papers described in TFA refute this.
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