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Ice age to interglacial period: Greatest climate change

The greatest climate change ever recorded by the world over the last 100,000 years has been the transition from the ice age to the warm interglacial period.

New research from the Niels Bohr Institute at the University of Copenhagen indicates that, contrary to previous opinion, the rise in temperature and the rise in the atmospheric carbon dioxide (CO2) follow each other closely in terms of time.

In the warmer climate, the atmospheric content of CO2 is naturally higher. CO2 is a green-house gas that absorbs heat radiation from the Earth and thus keeps the planet warm. In the shift between ice ages and interglacial periods the atmospheric content of CO2 helps to intensify the natural climate variations, the journal Climate of the Past reports.

It had previously been thought that as the temperature began to rise at the end of the ice age approximately 19,000 years ago, an increase in the amount of CO2 in the atmosphere followed with a delay of up to 1,000 years, according to a Copenhagen statement.

"Our analyses of ice cores from the ice sheet in Antarctica shows that the concentration of CO2 in the atmosphere follows the rise in Antarctic temperatures very closely and is staggered by a few hundred years at most," explains Sune Olander Rasmussen, associate professor and centre coordinator at the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen.

The research, which was carried out in collaboration with the University of Tasmania, Australia, is based on measurements of ice cores from five boreholes through the ice sheet in Antarctica. The ice sheet is formed by snow that doesn't melt, but remains year after year and is gradually compressed into kilometres-thick ice.