An ancient Earth like ours

August 9, 2010, University of Leicester
This is a specimen of the chitinozoan species Armoricochitina nigerica (length = c. 0.3mm). Chitinozoans are microfossils of marine zooplankton in the Ordovician. Their distribution allows to track climate belts in deep time, much in a way that zooplankton has been used for climate modeling in the Cenozoic. A. nigerica is an important component of the Polar Fauna during the late Ordovician Hirnantian glaciation. Credit: University of Leicester

An international team of scientists including Mark Williams and Jan Zalasiewicz of the Geology Department of the University of Leicester, and led by Dr. Thijs Vandenbroucke, formerly of Leicester and now at the University of Lille 1 (France), has reconstructed the Earth's climate belts of the late Ordovician Period, between 460 and 445 million years ago.

The findings have been published online in the Proceedings of the National Academy of Sciences of the USA - and show that these belts were surprisingly like those of the present.

The researchers state: "The world of the ancient past had been thought by scientists to differ from ours in many respects, including having carbon dioxide levels much higher - over twenty times as high - than those of the present. However, it is very hard to deduce carbon dioxide levels with any accuracy from such ancient rocks, and it was known that there was a paradox, for the late Ordovician was known to include a brief, intense glaciation - something difficult to envisage in a world with high levels of . "

The team of scientists looked at the global distribution of common, but mysterious fossils called chitinozoans - probably the egg-cases of extinct planktonic animals - before and during this Ordovician glaciation. They found a pattern that revealed the position of ancient climate belts, including such features as the polar front, which separates cold polar waters from more temperate ones at lower latitudes. The position of these climate belts changed as the Earth entered the Ordovician glaciation - but in a pattern very similar to that which happened in oceans much more recently, as they adjusted to the glacial and interglacial phases of our current (and ongoing) Ice Age.

This 'modern-looking' pattern suggests that those ancient levels could not have been as high as previously thought, but were more modest, at about five times current levels (they would have had to be somewhat higher than today's, because the sun in those far-off times shone less brightly).

"These ancient, but modern-looking oceans emphasise the stability of Earth's atmosphere and climate through deep time - and show the current man-made rise in greenhouse gas levels to be an even more striking phenomenon than was thought," the researchers conclude.

Explore further: Geologists demonstrate extent of ancient ice age

More information: Vandenbroucke, T.R.A., Armstrong, H.A., Williams, M., Paris, F., Zalasiewicz, J.A., Sabbe, K., Nolvak, J., Challands, T.J., Verniers, J. & Servais, T. 2010. Polar front shift and atmospheric CO2 during the glacial maximum of the Early Paleozoic Icehouse. PNAS doi:10.1073/pnas.1003220107.

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4.7 / 5 (3) Aug 09, 2010
This article mentions that the sun shone less brightly about 450 million years ago. What is the explanation for a fainter sun in the distant past? I am curious!
3 / 5 (3) Aug 09, 2010
This article mentions that the sun shone less brightly about 450 million years ago. What is the explanation for a fainter sun in the distant past? I am curious!

Theories include:

1.) Higher greenhouse effect resulting in higher temperatures despite lower solar activity.

2.) Fewer clouds and land meant less sunlight was reflected out into space.

3.) Earth may have seen cyclic freezing and oceans freezing over as recently as 630 million years ago before the Cambrian explosion.

4.) Many other less accepted theories or a combination of those and the theories listed above.
5 / 5 (2) Aug 09, 2010
Thanks Trekgreek1 but this article mentions that the sun shone less brightly, I have also read this from some other sources. What I am wondering about is why the sun shone less brightly in our early younger solar system?

One would think a newly formed star would shine more intensely in its early life when its percentage of hydrogen would be at its highest.
3 / 5 (1) Aug 09, 2010
Hey Question, I believe that the 'evolution' of a star is based on the material that it is fusing to create the light at the moment in question.
4 / 5 (2) Aug 09, 2010
this is truly bad news for the earth's climate and the effects us humans are having on it.
5 / 5 (2) Aug 09, 2010
current events in Pakistan, Russia, and Europe point towards a catastrophic shift in accepted weather patterns. Here in Western Australia we have just had our driest winter on record, and the lowest recorded dam runoff amounts ever. Whilst we were having an imbecilic argument about whether or not it really was happening - it's happened!
5 / 5 (5) Aug 10, 2010
What is the explanation for a fainter sun in the distant past?

That is the way suns appear to function. As they age they heat up.


5 / 5 (1) Aug 10, 2010
Thanks for the two excellent links Ethelred.
5 / 5 (1) Aug 10, 2010
This article mentions that the sun shone less brightly about 450 million years ago. What is the explanation for a fainter sun in the distant past? I am curious!

As stars mature they burn hotter and hotter as hydrogen fuel is spent and helium based nucleosynthesis becomes more and more common.
3 / 5 (1) Aug 11, 2010
Nobody claims climate change is not a fact! the question is what is the cause. I submit that we should admit our ingnorance. clearly i could walk
from location of london to the location of paris
ten thousand years ago and all of usa north of boston was covered a mile deep in ice.

weather observations are not evidence of climatic change unless they can be viewed in a 1000 yr. period.
5 / 5 (2) Aug 11, 2010
That's a ridiculous argument, po6ert. It's like saying "nobody claims evolution isn't a fact, we just have absolutely no idea about it, God probably did it all, and we really won't know for at least a thousand years."

By your definition, the average global temperature could rise 500 degrees and we would be unable to proclaim a change in climate until 1,000 years had passed.
5 / 5 (1) Aug 12, 2010
po6ert, normally you read the article, then post a response...
5 / 5 (1) Aug 16, 2010
Actually, climate is better understood today than just 5 years ago, thanks to new very powerful computers, and appropriate computer programs that are able to model climate.
That we are able to decipher the sparse geological clues to climate in the Ordovician, using fossil trace evidence, to the point where the positions of the polar fronts over time can be tracked is a major achievement.
Confining the upper limit to the carbon dioxide levels half a billion years ago -when the sun was measurably fainter than today- is a triumph that sadly may not be obvious for people raised with inaccurate descriptions of science in films and TV. Kudos to the team!

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