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The temperature curve through the Greenland inland ice sheet shows 26 dramatic and abrupt climate shifts during the last ice age that lasted more than 100.000 years. This curve shows the climate shifts during 40,000 years. The climate shifts appear to be periodic, but mathematical computer simulations shows that they are probably chaotic and random. (Credit: Peter Ditlevsen)

ScienceDaily (Mar. 10, 2007) — Severe climate changes during the last ice-age could have been caused by random chaotic variations on Earth and not governed by external periodic influences from the Sun. This has been shown in new calculations by a researcher at the Niels Bohr Institute, Copenhagen University.

Several large international projects have succeeded in drilling ice-cores from the top of the Greenland inland ice through the more than 3 km thick ice sheet. The ice is a frozen archive of the climate of the past, which has been dated back all the way to the previous interglacial Eem-period more than 120.000 years ago.

The ice archive shows that the climate has experienced very severe changes during the glacial period. During the glacial period there were 26 abrupt temperature increases of about 7-10 degrees. These glacial warm periods are named Dansgaard-Oeschger events after the two scientists first observing them.

This thought-provoking article can be read in its entirety here.