Sun may be giving Earth the cold shoulder

by mdr on Jan. 26th, 2007
in Earth and Space Science and The Water Cycle, Weather and Climate

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The Sun: Image courtesy NASATemperature fluctuations inside the sun appear to coincide exactly with the frequency of ice ages here on Earth, according to physicist Robert Ehrlich of George Mason University in Fairfax, Virginia.

Generally it’s been thought that temperatures in the sun’s interior remain constant due to the opposing forces produced by gravitation and nuclear fusion. Ehrlich created a computer model of the sun that shows instabilities in the solar plasma, caused by fluctuations in the core’s magnetic fields, could result in long-termed temperature variations. He based his model on the work of Attila Grandpierre, a specialist in solar physics at the Konkoly Observatory of the Hungarian Academy of Sciences.

The model shows that most of the core’s oscillations seem to cancel each other out, but some strengthen one another and allow the sun’s core temperature to waffle around it’s average of 13.6 million degrees Kelvin in cycles of roughly either 100,000 or 41,000 years.

These timescales coincide with the frequencies ice ages have occurred on Earth. Over the past million years terrestrial cooling periods have occurred about every 100,000 years. Before that, the ice ages came about every 41,000 years.

While scientists have long theorized that the ice ages were the result of changes in the Earth’s orbit around the sun known as Milankovitch cycles , Ehrlich questions how those changes (from circular to slightly oval-shaped) would explain the shift from frequencies of the ice ages.

Neil Edwards, a UK climatologist at the Open University in Milton Keynes tends to agree. "In Milankovitch, there is certainly no good idea why the frequency should change from one to another," he said.

But Edwards doesn’t agree with Ehrlich’s assertion that temperature swings created by Milankovitch cycles just aren’t large enough to produce ice ages. He believes that Earth processes could amplify the effects of the orbital changes and result in long periods of cooler temperatures.

"If you add their effects together, there is more than enough feedback to make Milankovitch work," Edward said. "Milankovitch cycles give us ice ages roughly when we observe them to happen. We can calculate where we are in the cycle and compare it with observation," he says. But he added that he couldn't see any way of testing Ehrlich’s idea to see where the sun is in the temperature oscillation.

Ehrlich concedes that the shift in frequencies is too gradual to observe on our sun, but he believes it’s possible the oscillations could be observable in distant, smaller stars known as red dwarfs.

FURTHER INFO
More on Milankovitch Cycles
The Great Ice Age
New Scientist

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