Earth's polar temperature has swung wildly—by as much as 15 degrees Celsius (59 degrees Fahrenheit)—over the last 800,000 years, an Antarctic ice core has revealed.
In 2004 scientists led by Jean Jouzel of the Laboratory of Climate and Environmental Sciences (LSCE) in Gif-sur-Yvette, France, pulled up the final chunk of ice core from a drill hole in the center of Antarctica.
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Measuring deuterium, a form of the element hydrogen, enabled the team to piece together the temperature record in the ancient ice.
The new climate record covers an additional cycle of glacial change, amounting to 11 cycles in total, lead author Jouzel said.
Plugging the data from the entire core into an atmospheric model, the scientists were able to reconstruct a reliable temperature record for the past 800,000 years.
In today's online journal Science, the team showed that the coldest period occurred around 20,000 years ago, during the last glacial maximum, when the ice sheets were at their peak.
It was about 10 degrees Celsius (50 degrees Fahrenheit) colder than today. (Related: "Antarctica's Atmosphere Warming Dramatically, Study Finds" [March 30, 2006].)
Meanwhile, the warmest period was during the last interglacial period, which is an interval of warmer global average temperature that separates ice ages. At that time, around 130,000 years ago, it was a balmy 4.5 degrees Celsius (8.1 degrees Fahrenheit) warmer than today.
Remember when reading this that + 4.5 C is local to Antarctica. Not all the Earth warms or cools at the same rate.
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