The new ice core, announced June 9 by the European Project for Ice Coring in Antarctica, or EPICA, reaches far enough back in time to give scientists "a first shot at looking at climate and greenhouse gases during interglacial periods when humans had nothing to do with climate change," said geological sciences Professor James White.

"This has the potential to separate the human-caused impacts from the natural and place it in a much clearer context," he said.

A commentary on the new ice core written by White will appear in the June 11 edition of the journal Science. One of the world's leading ice-core scientists, White has conducted dozens of studies of ice cores from both Antarctica and Greenland. He is director of the CU-Boulder Environmental Studies program and a fellow of the CU-Boulder Institute of Arctic and Alpine Research.

Concern about the effects of human-caused greenhouse gas releases into the atmosphere has led many scientists to conclude that humans are changing the atmosphere. Drilling deep into polar regions and extracting ice cores can tell scientists about the Earth's climate during the distant past, before technology and farming became a factor in releasing such gases.

Ice cores can tell scientists about concentrations of greenhouse gases such as carbon dioxide and methane, dust levels in the atmosphere, volcanic eruptions and estimates of temperatures and precipitation.

"We're living in an unusual time," White said. "In the past 430,000 years, the percentage of time that the climate was as warm as it is today is quite small, about 5 percent to 10 percent, and before that time, it appears to never have been that warm.

"Humans have been active in messing with the carbon cycle for a long period of time," he said. "Here we are warming the planet, while at the same time, climatologists will tell us that we are perhaps long overdue for a glacial period."

The average number of years spent in a warm period between ice ages - like our current climate -- has been about 6,000 years, White said. But the current interglacial period has lasted for 12,000 years. Only one other interglacial period has exceeded that length of time - it lasted for about 28,000 years - and it happened about 450,000 years ago.

The EPICA core will provide the first complete record of that period and will allow scientists to study it in more detail than ever before, White said.

"Ice cores are the ultimate preservation tool for information about past environments," White said. "Whatever happens on the Earth that changes the atmosphere - the big events - is recorded in the ice and it stays there."

Another exciting aspect of the EPICA ice core is that at 740,000 years, scientists have not yet reached the bottom of the ice sheet, he said. "The possibility of a million-year ice core is out there and a million years ago is a really significant period in the Earth's climate history."

Prior to a million years ago, there was no large-scale glacial/interglacial pattern and the Earth had a more steady climate controlled by the sun, he said. Something happened at around that time to cause the Earth to have larger variations in its climate.

"One of our biggest scientific questions is: Is glaciation overdue?" White said. "For our future it is very important that we understand how these huge glaciers start."

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