How did the ice age begin

Not a result of too much carbon dioxide

Glaciers and icebergs

Los Angeles (USA) - The glaciers of the last Ice Age began to melt around 18,000 years ago. Climate change as a result of more carbon dioxide in the atmosphere has long been considered to be the cause of the end of the last ice age. But that's not true, American climate researchers have now discovered. In a preliminary publication of the journal "Science" they report that the cause is rather to be found in the current climate in the southern hemisphere.

"You can no longer blame carbon dioxide (CO2) alone for the end of the Ice Age," says geologist Lowell Stott of the University of Southern California in Los Angeles. From the analysis of lake sediments from the Pacific, the researchers recognized that temperatures in the deep sea had already increased by around two degrees 1,300 years before a demonstrably higher CO2 concentration in the atmosphere. A water current from the Antarctic region is responsible for this with a warming effect comparable to that of the Gulf Stream today.

The warming of the waters in the southern hemisphere is caused by a higher absorption of the warming solar radiation. Because parallel to the rising water temperatures, the sea ice there is said to have receded, which previously reflected the solar radiation back into space.

This study shows how regional climate effects can have a global impact. Despite the incipient warming by a deep sea current, carbon dioxide also played an important role in the further course of the fading Ice Age. Because the onset of warming released more of the climate gas and accelerated the further decline of the glaciers from Central Europe.