Climate change - a random event?

Some interesting news from the Niels Bohr Institute at Copenhagen University. From Science Daily:

Climate Change: Could It Be Random?
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.

The global warming we experience presently will cause a temperature increase of perhaps 2-5 degrees in the next century if greenhouse gas emissions continue, researchers claim. This will lead to increased sea levels and more severe weather with terrible consequences. The temperature rise during the glacial period were much larger and happened much faster.

Temperature increased by 10 degrees in less than 50 years with changes to the ocean currents and the whole ecosystem. These changes have caused sea level rises up to perhaps as much as 8 meters and large changes to the vegetation.

There is no one factor at work here but a complex network. Reading stuff like this makes me realize just how crude the climate models are -- how many variables are, purposely or not, left out or minimized.