Potsdam, 20 May 2003
During the last Ice Age, which ended ten thousand years ago, over
twenty abrupt and dramatic warmings have occurred. These so-called
Dansgaard-Oeschger-events show a striking and puzzling regularity, as
climatologist Stefan Rahmstorf of the Potsdam Institute for Climate
Impact Research (PIK) in Germany shows in a new study published this
week in Geophysical Research Letters.
Dansgaard-Oeschger-(or DO-)events are the perhaps most dramatic climate
shifts known: starting from frosty Ice Age conditions, they involve
sudden warmings of up to ten degrees Centigrade within a decade or two.
The anomalous warmth then typically lasted for several centuries. The
leading theory to explain these warmings involves a northward push of
warm Atlantic waters towards the Arctic, into the Greenland and
Norwegian Seas (see press releases of 5 January 2001 and 18 January
2002). But the ultimate trigger of such changes in ocean currents
remains unknown.
In a new study of Greenland ice core data, Rahmstorf has now unvailed
an intriguing clue: the warm events appear to be paced by an extremely
regular cycle of 1,470 years duration. This cycle does not trigger a DO
event each time; in 23 investigated cycles only 13 events were
triggered. The existence of such a cycle had been noticed before, yet
the high regularity revealed by the new analysis came as a surprise.
The length of the cycle is maintained constant within a few percent of
1,470 years over a time interval of at least 35,000 years.
Such regularity points strongly to an extraterrestrial origin of this
cycle - perhaps an orbital cycle. "No oscillation within the Earth
system could be so regular," says Rahmstorf. "Even the known solar
cycles show greater variations in their periods."
The hunt is now on to find an orbital cycle with a period of 1,470 years, since such a cycle is so far not known.
The Potsdam Institute for Climate Impact Research (PIK) was founded in
1992 and employs 121 scientists. Its research on climate change,
climate impacts and sustainable development is of international renown.
PIK is a member of the Leibniz Association.
Contact:
Prof. Dr. Stefan Rahmstorf, stefan.rahmstorf@pik-potsdam.de, Tel. +49/331/288-2688
Press office:
Anja Wirsing, anja.wirsing@pik-potsdam.de, Tel. +49/331/288-2507
Original article:
Rahmstorf, Stefan 2003: Timing of abrupt climate change: A precise clock. Geophysical Research Letters, Vol. 30, No. 10.
The article can be viewed on the internet:
http://www.pik-potsdam.de/~stefan/Publications/Journals/rahmstorf_grl_2003.pdf
The reproduction of this text is permitted free of charge.
