1.4 billion years old forces are causing climate change today
Scientists have found evidence that the same natural forces that are causing climate changes today made the climate turbulent 1.4 billion years ago.
Ice ages and warm periods come and go at regular intervals -- and that is probably the way it has always been.
This theory is strengthened by new research which demonstrates that climate cycles are by no means a “modern” phenomenon.
”It has been the assumption that these forces existed way back in the Earth’s past, but you don’t really know until you’ve proven it. We’ve done so now, which is pretty spectacular,” says Professor Donald Eugene Canfield, from the Department of Biology at the University of Southern Denmark.
Sheds light on the history of the Earth
According to Canfield, the study can tell us a lot about the climate in the past and help us to understand how historic climate changes have influenced the Earth’s geology and through that, its biology.
The scientist points out that the study is not, on the other hand, much use when it comes to present day man-made climate changes.
”It’s not so much its relevance in relation to the current climate debate as it is in relation to understanding how the climate has developed during the course of the Earth’s geological history,” says Canfield.
One of the big questions regarding the climate of the past is why ice ages occurred in some geological periods and not in others.
Climate concealed in Chinese mountains
In their study the scientists used rock formations in northern China (the Xiamaling Formation) to determine whether Milankovitch cycles (variations in the orbit of the Earth) changed wind and oceanic circulation on Earth 1.4 billion years ago.
The Xiamaling Formations took shape when different minerals and organic material formed a layered sea bed, which over billions of years ended up as the rocks that make up Xiamaling.
By dating the individual strata and studying their content of mineral and organic material the scientists were able to establish that the fluctuations in the climate that occurred as long as 1.4 billion years ago correspond to the Milankovitch cycles we see today.
"We can see that the fluctuations were shorter-lasting in the past than the Milankovitch cycles are today. This is probably because the Moon was closer to the Earth back then," says Canfield.
More evidence needed
Assistant professor Peter Ditlevsen from the Niels Bohr Institute, University of Copenhagen has read the study and finds it interesting that the scientists have found apparent evidence of Milankovitch cycles 1.4 billion years ago.
He has his reservations, however.
"It's interesting that the researchers can see these cyclic events so far back in time. But it has to be said that when looking so far back, the result does become subject to some uncertainty," says Ditlevsen.
"For one thing, it's difficult to say what the periods in the Earth's path around the Sun were so long ago. And secondly, because the climate's dependence of the Milankovitch cycles is very complicated.”
“So I believe the results are extremely interesting if it’s possible to use precise dating to determine the periodicity of the climate change so far back in time," he says.
Read the original story in Danish on Videnskab.dk
Translated by: Hugh Matthews
- http://www.pnas.org/content/early/2015/03/06/1502239112.abstract, PNAS, doi: 10.1073/pnas.1502239112