This is an archive of AGU's GeoSpace blog through 1 July 2020. New content about AGU research can be found on Eos and the AGU newsroom.

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13 May 2019

La Niña’s effect on droughts can be traced back to U.S. Civil War

The Civil War drought – one of the worst to afflict the U.S. in centuries – occurred in the mid-1850s to the mid-1860s. That drought is infamous for its effects in the U.S. Southwest and parts of the Great Plains, where it led to the near extinction of the American bison and played an important role in changing the course of the Civil War by causing food and water shortages, slowing the advance of part of the Confederate army in 1862.


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17 December 2015

Preserved trees that grew 12,000 years ago improve radiocarbon dating calibrations

Scientists use radiocarbon dating to determine the age of everything from bone and teeth to seeds and straw. The accuracy and precision of those dates depends on careful calibration. New data from logs unearthed in a small floodplain in New York’s Lake Ontario lowlands will allow scientists to refine the calibrations for a 1,200 year period that occurred about 12,000 years ago, according to Carol Griggs, a dendrochronologist at Cornell University in Ithaca, New York.

The record represents “a new independent radiocarbon series for this time period,” Griggs said at the 2015 American Geophysical Union Fall Meeting in San Francisco.


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21 December 2010

A (really really) Old Farmer’s Almanac: A record of specific weather patterns 55 million years ago

San Francisco will be rainy through this week, but I am learning about weather 55 million years ago, as recorded in the rings of ancient trees found in a coal seam on Ellesmere Island, above the Arctic Circle.

The trees caught the interest of University of Hawaii geologists Hope Jahren and Brian Schubert and their collaborators. “The wood is of spectacular preservation,“ Jahren said during her Thursday afternoon talk given in session B44B. “This is mummified wood”–wood that somehow avoided petrification.


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