Sixty-six million years ago, after a huge asteroid hit the Earth with the explosive energy of approx 1 billion nuclear bombs, a veil of ash, dust and vaporized rock covered the sky and it rained slowly on the planet. While the animal and plant species died in bulk, tiny underwater amoebae called foramina have continued to reproduce, building robust shells with calcium and other deep-sea minerals, just as they had done for hundreds of millions of years. When each foramen inevitably died – pulverized into sediments on the seabed – it kept a small piece of Earth’s ancient history alive in their fossilized shells.
For decades, scientists have studied those shells, finding clues to ancient Earth̵
The new paper, which includes decades of deep-sea drilling missions in a single record, details the Earth’s climatic swings throughout the It was Cenozoic – the 66 million year period that began with the death of dinosaurs and extends to the current age of human supply climate change. The results show how Earth passed through four distinct climate states – dubbed the Warmhouse, Hothouse, Coolhouse and Icehouse states – in response to changes in the planet’s orbit. greenhouse gases levels and the extent of the polar caps.
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The zigzag graph (shown above) ends with a sobering spike. According to the researchers, the current pace of anthropogenic global warming it far exceeds the natural climatic fluctuations observed at any other time in the Cenozoic era and has the potential to drive our planet out of a long icebox phase into a scorching greenhouse state.
“Now that we have been able to capture the variability of the natural climate, we can see that the predicted anthropogenic warming will be much greater than that,” study co-author James Zachos, professor of earth and planet sciences at the University of California, Santa Cruz, he said in a statement. “The Intergovernmental Panel on Climate Change (IPCC) projections for 2300 in the business-as-usual scenario, it will potentially bring global temperature to a level the planet has not seen in 50 million years. “(The IPCC is a United Nations group that evaluates the science, risks and impacts of climate change on the planet.)
In the greenhouse
To compile their new climate map of an era, the study authors examined the shells of fossil foramen in deep-sea sediment cores – long tubes of rock, sediment and microbes – drilled by the world’s oceans in recent decades. Forams (short for foraminifera) are microscopic plankton whose oldest relatives appeared in the ocean nearly a billion years ago; the deeper scientists dig into the seabed, the older the specimens of foramina they discover.
The reports of carbon is oxygen the isotopes (versions of the elements) in the shells of the foramina contain critical climatic information. The ratio of oxygen isotopes oxygen-18 to oxygen-16, for example, can reveal how hot the surrounding water was when a foramen built its shell; the higher the ratio, the colder the water. The ratio of carbon-13 to carbon-12 shows how much organic carbon was available for the microbes to eat; here, a higher ratio correlates with more greenhouse gases (such as carbon dioxide) in the atmosphere.
Because the team’s climate record covers such an incredibly long period of time, the researchers also had to consider astronomical impacts on the planet’s climate – how the slowly changing orbit and tilt towards the sun affect the amount of sunlight. which reaches the different parts of the planet. at different times, also known as Milankovitch cycles. When the team overlayed the orbital data with their own isotopic climate data, they saw that the orbital variations created distinct but relatively small-scale changes to the global climate. Basically, every big leap between climatic states has been tied to a massive change in greenhouse gases levels, the researchers said.
For example, about 10 million years after the extinction of the dinosaurs, Land it has gone from a greenhouse state to a greenhouse state. This event, known as the Paleocene-Eocene thermal maximum, saw temperatures as high as 60 degrees Fahrenheit (16 degrees Celsius) above modern levels, Zachos said, and was driven by a massive release of carbon into the atmosphere. , thought to be the result of massive volcanic eruptions in the North Atlantic. Similarly, when carbon dioxide disappeared from the atmosphere over the next 20 million years, ice sheets began to form. Antarctica and the planet has entered a phase of refrigeration, with surface temperatures averaging about 40 F (4 C) above modern levels.
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About 3 million years ago, the Earth entered an icebox phase, driven by the growth and decline of ice sheets in the Northern Hemisphere. Now, human emissions of greenhouse gases are causing temperatures to rise to an extent not seen in tens of millions of years. This increase is far beyond the natural variations triggered by the changing orbit of the Earth, the researchers concluded. And if current greenhouse gas emissions remain constant, the climate could skyrocket to levels never seen since the Paleocene-Eocene Thermal Maximum. The transition from icebox to greenhouse won’t take millions of years, Zachos said – it will take hundreds.
“We now know more precisely when it was warmest or coldest on the planet and we have a better understanding of the underlying dynamics and the processes that drive them,” study lead author Thomas Westerhold, director of the Marine Environmental Sciences Center. University of Bremen in Germany, said in the statement. “Time from 66 [million] 34 million years ago, when the planet was significantly warmer than it is today, is of particular interest, as it represents a parallel in the past to what future anthropogenic change could lead to. “
Originally published on LiveScience.