Climate: Solar activity not crucial

Ice core provides information on climate factors of the last 800, 000 years

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The Antarctic ice core of the EPICA project is 3, 260 meters long and lasts 800, 000 years in the Antarctic climate past. His analysis shows not only a change in the rhythm of climate fluctuations 400, 000 years ago, it also reveals that the sun played only a minor role as a climatic factor. The research results were published in "Science Express".

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Since 1996, the Department of Environmental and Environmental Physics of the Physics Institute of the University of Bern has been significantly involved in the European ice core drilling project EPICA (European Project for Ice Coring in Antarctica). The drilling provides insight into the evolution of the Earth's climate over the last 800, 000 years. This is the longest climate history ever, reconstructed from ice cores.

Nick 400, 000 years ago

The analysis of the data from the 3, 260-meter-long ice core of Dome Concordia in the eastern Antarctic now clearly shows that the Earth's climate hit a new rhythm 400, 000 years ago. In the period from 800, 000 years ago to 400, 000 years ago, the climate tended to fluctuate in a 40, 000-year rhythm with cooler, but longer-lasting warm periods. However, this was followed by four significantly longer climate cycles of around 100, 000 years each.

The new measurements on the EPICA core together with climate models allow a better estimation of the temperature changes associated with climate variability. The coldest period 20, 000 years ago was about 10 ° C below today's level. The warmest period about 130, 000 years ago was about 4.5 ° C warmer than today. display

North-South climate swing during the last 800, 000 years

The Bern scientists are also significantly involved in research on the climate coupling between the northern hemisphere and the southern hemisphere (north-south climate swing). In earlier climatic cycles, there are strong similarities to the behavior observed in the last ice age (100, 000 to 11, 000 years ago): The large temperature fluctuations in the North Atlantic region at that time are recognizable as weaker, temporally shifted fluctuations in the Antarctic, as predicted by the Bernese model has been.

Astronomical factors more important than luminosity fluctuations of the sun

The latest results also confirm that the "natural", non-man-made climatic variations are mainly determined by astronomical factors such as the inclination of the Earth's axis. Other influences, such as volcanism and changes in the luminosity of the sun, on the other hand play a minor role in natural climatic fluctuations.

The temperature reconstructions now available serve as a reference for the further evaluation of the ice core, for example for records of greenhouse gases or other atmospheric trace substances. As part of the European project EPICA, the Bernese team carried out such carbon dioxide and methane measurements.

(University of Bern, 09.07.2007 - NPO)