Solar radiation caused periodic ice ages to end 19,000 years ago

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Washington, August 7 (ANI): In a new research, scientists have concluded that slight shifts in solar radiation caused by predictable changes in Earth's rotation and axis made the periodic ice ages to finally come to an end about 19,000 years ago.

The research, by scientists from Oregon State University and other institutions conclude that the known wobbles in Earth's rotation caused global ice levels to reach their peak about 26,000 years ago, stabilize for 7,000 years and then begin melting 19,000 years ago, eventually bringing to an end the last ice age.

The melting was first caused by more solar radiation, not changes in carbon dioxide levels or ocean temperatures, as some scientists have suggested in recent years.

"Solar radiation was the trigger that started the ice melting, that's now pretty certain," said Peter Clark, a professor of geosciences at OSU.

According to scientists, the findings are important because they will give researchers a more precise understanding of how ice sheets melt in response to radiative forcing mechanisms.

Even though the changes that occurred 19,000 years ago were due to increased solar radiation, that amount of heating can be translated into what is expected from current increases in greenhouse gas levels, and help scientists more accurately project how Earth's existing ice sheets will react in the future.

"We now know with much more certainty how ancient ice sheets responded to solar radiation, and that will be very useful in better understanding what the future holds," Clark said. "It's good to get this pinned down," he added.

To make their analysis, the researchers used an analysis of 6,000 dates and locations of ice sheets to define, with a high level of accuracy, when they started to melt.

In doing this, they confirmed a theory that was first developed more than 50 years ago that pointed to small but definable changes in Earth's rotation as the trigger for ice ages.

"We can calculate changes in the Earth's axis and rotation that go back 50 million years," Clark said.

"These are caused primarily by the gravitational influences of the larger planets, such as Jupiter and Saturn, which pull and tug on the Earth in slightly different ways over periods of thousands of years," he added.

That, in turn, can change the Earth's axis - the way it tilts towards the sun - about two degrees over long periods of time, which changes the way sunlight strikes the planet.

Those small shifts in solar radiation were all it took to cause multiple ice ages during about the past 2.5 million years on Earth, which reach their extremes every 100,000 years or so. (ANI)

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