Is the Earth's climate theory over the last 15 million years wrong?

According to a study conducted by Rutgers, a key theory that attributes the evolution of the Earth's climate to the degradation of the Himalayan rocks might not explain the cooling of the last 15 million years.

The study in the newspaper Nature Geoscience could shed more light on the causes of climate change in the long term. It focuses on the long-term cooling that occurred prior to recent global warming related to humanity's greenhouse gas emissions.

"The findings of our study, if corroborated, raise more questions than answers," said lead author Yair Rosenthal, Distinguished Professor of the Department of Marine and Coastal Sciences of the School of Environmental Science and Science. Biology of Rutgers University of New Brunswick. "If the cooling is not due to the improved weathering of the Himalayan rock, what processes have been forgotten?"

For decades, the main assumption has been that the collision of the Indian and Asian continents and the elevation of the Himalayas have brought fresh rocks to the surface of the Earth, making them more vulnerable to rain. alteration by carbon dioxide, an essential greenhouse gas. But this hypothesis remains unconfirmed.

Lead author Weimin Si, a former doctoral student at Rutgers, today at Brown University, and Rosenthal challenged this hypothesis and examined the sediments of the deep sea bottoms rich in calcium carbonate.

For millions of years, alteration of captured rocks captured carbon dioxide and rivers carried it into the ocean as dissolved inorganic carbon, used by algae to build their calcium carbonate shell. When the algae die, their skeletons fall to the bottom of the sea and are buried, thus blocking the carbon from the atmosphere in the sediments of the deep seabed.

If atmospheric alteration increases, the accumulation of calcium carbonate in shallow waters is expected to increase. However, after studying dozens of sediment cores on the high seas as part of an international ocean drilling program, Si discovered that calcium carbonate in shells had declined dramatically in 15 million years , suggesting that rock weathering may not be responsible for long-term cooling.

Surprisingly, scientists have also discovered that algae, called coccolithophores, were adapted to reduce carbon dioxide in 15 million years by reducing their production of calcium carbonate. This reduction has apparently not been taken into account in previous studies.

Many scientists believe that ocean acidification caused by high levels of carbon dioxide will reduce the calcium carbonate contained in algae, especially in the near future. The data suggests, however, that the opposite has occurred in the 15 million years that preceded the current global warming.

The Rosenthal lab is now trying to answer these questions by studying the evolution of calcium and other elements in the ocean.