Friday, 6 July 2007

Ancient DNA hints at natural warming

by CRAIG BROWN

A SCIENTIST yesterday claimed climate change could be caused by natural conditions after finding ancient DNA in Greenland, which indicates the region was much warmer during the Ice Age than previously thought.

Martin Sharp, a glaciologist at the University of Alberta, made the claim after taking part in an international research project that collected the oldest ever-recorded DNA samples.

He had previously supported the idea that global warming was caused by humans but the project raised some doubts.

The DNA was discovered at the bottom of a 2km-thick ice sheet and came from trees, plants and insects of a boreal forest estimated to be between 450,000 and 900,000 years old.

Ice underneath the glacier created a natural freezer, which had preserved the DNA samples.

They suggest the temperature of the southern Greenland boreal forests at the time was probably between 10C in summer and -17C in winter.

The reduced glacier cover means the global ocean was probably also between one and two metres higher during that time compared with current levels.

Mr Sharp said: "These findings allow us to make a more accurate environmental reconstruction of the time period from which these samples were taken, and what we've learned is that this part of the world was significantly warmer than most people thought."

He now believes there is evidence climate warming on the current scale is possible through natural conditions.

He said: "It could mean that our current warming is the result of both natural processes and human influences, and we may be heading for even bigger temperature increases than we previously thought."


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