Was Croll Even More Right? Sorta?

New ice cores from the deep Antarctic show a direct and millennia-old relationship between climate changes in the northern and southern hemispheres, scientists said on Wednesday.

Comparison with cores from Greenland proves a strong north-south link and also highlights the role of the meridional overturning circulation (MOC) -- the so-called Atlantic Conveyor -- in the process of heat transfer.

"It is really astounding how systematic this process worked also for smaller temperature changes in the Antarctic," said team leader Hubertus Fischer from the Alfred-Wegener Institute for Polar and Marine Research in Bremerhaven, Germany.

Climate changes in the northern hemisphere have already been well documented through ice cores from Greenland, but until recently there was only sketchy evidence from Antarctica to show southern hemisphere variations.

Now a team from the 10-nation European Project for Ice Coring in Antarctica has drilled out a core covering a period of 150,000 years from an area of the frozen continent where plentiful annual snowfalls allow detailed analysis.

They found that even short and small temperature changes in the south were connected to fast changes in the north by the changing Atlantic currents.

The MOC carries warm water from the southern hemisphere northwards bringing heat to northern climes.

When the warm water current meets the Greenland ice sheet it cools and sinks, heading south again and driving the conveyor belt process.

"Our data shows that the degree of warming in the south is linearly related to the duration of cold periods in the North Atlantic," Fischer said, describing the process as a "bipolar seesaw."

Antarctica warmed several times between 20,000 and 55,000 years ago while the north was cold and export of warm water from the southern ocean was reduced.

By contrast, Antarctica started to cool every time more warm water started to flow into the north Atlantic during warm events in the north.

The data, using analysis of methane concentrations trapped in the ice, was published in the science journal Nature.

He's Croll.