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Climate change it's even more complicated
Climate Climate Natural

Jupiter and Venus have been influencing the climate on earth for at least 215 million years

About a century ago, mathematician Milutin Milanković wrote about astronomical processes that cause cyclical climate changes. Now evidence has been found that Jupiter and Venus have been influencing our climate since the early dinosaur era, write American geologists in the journal PNAS.

Jupiter and Venus are more than bright lights in the night sky, their effect on the orbit of the earth has been responsible for climate change on our planet for at least 215 million years.
Red planet Venus

Almost a century ago, the Serbian mathematician Milutin Milanković predicted long, rhythmic changes in the climate caused by fluctuations in the movement of the earth around the sun. Now a team of American geologists has found 215 million years of evidence for one of those climate cycles. This can help us better understand the history of the earth and that of the solar system.

The cycle in question is caused by the gravitational force of the great gas giant Jupiter and our neighboring planet Venus on the earth. They make sure that the orbit in which the earth revolves around the sun is sometimes more outrageous than usual. On a human scale, we notice almost nothing of that change - one cycle from most elliptical to most round and back takes 405,000 years - but this is very interesting for geologists and astrophysicists.
Globe with colorful clouds

Rocket science

Although we have known the cycle for a long time, it was not yet certain that he was always so stable. The mathematical model of this cycle - based on movements of the celestial bodies - is, according to astrophysicists, reliable until 'only' 50 million years ago.

"We basically use the same math’s as those with which we send space probes to Mars, and okay, that works," says researcher Paul Olsen of Columbia University in New York. But moving these movements back millions of years and connecting climate change there is something we have not yet fully figured out. The retrieval of such a cycle in old rock layers can help to pull apart the tangle of astronomical movements.
Man holding a core containing red colored sediment
A fresh core contains red-colored sediments deposited more than 200 million years ago.

The final evidence came from drill cores: pieces of stone that were taken up from the ground with hollow tubes. Those stones came from more than 450 meters underground in the Petrified Forest National Park in Arizona and out of rocks that had previously been mined in New York and New Jersey. In those last nuclei the cycle was already visible, but it could not yet be proven that they actually lasted 405,000 years.

The Arizona cores provide that evidence, because layers of volcanic ash between the deposits contain radioactive isotopes. Because those isotopes decay in a very predictable way, you can calculate how old the layers are. These ages allowed the researchers to extrapolate to the other centers, with which they could prove that they really had found a cycle of 405,000 years.

Artist’s depiction of Savannasaurus elliottorum based on fossil remains Image by Travis Tischler / © Australian Age of Dinosaurs Museum of Natural History in landscape
Artist’s depiction of Savannasaurus elliottorum based on fossil remains Image by Travis Tischler / © Australian Age of Dinosaurs Museum of Natural History

The cycle now found has two brothers caused by changes in the orientation of the earth's axis. Those last two cycles, which last 'only' twenty and forty thousand years, are less stable and often more difficult to distinguish. 'The beauty of the 405,000-year cycle is that it is separate from the rest', says researcher Dennis Kent. "He does not change. The other cycles move over these. "

The Milankovitch cycles are a sort of yardstick for geologists for time: a worldwide system of alternations that always take about the same length of time. Regular changes in climate can be found in sedimentary deposits in various places. This allows you to link something that happened a long time ago to another event that took place somewhere else at the same time.

For example, the discovery of this cycle can help us better understand the rise of the dinosaurs - more than two hundred million years ago, the researchers write. With the help of the cycle, you can place the evolution of these powerful beasts and the changes that took place in their environment very precisely in the right time and compare them all over the world.

Emmeke Bos, Earth & Climate, Astronomy

Emmeke Bos studies earth science at VU University Amsterdam and is an intern at New Scientist.