66 million years ago, after a massive asteroid hit the Earth with the explosive energy of approx 1 billion atomic bombs, a casing of ash, dust, and evaporated rock covered the sky and slowly rained down on the planet. When plant and animal species died a lot, small underwater amoebas called forams continued to reproduce and built robust shells of calcium and other deep-sea minerals, just as they had done for hundreds of millions of years. When each foram inevitably died – powdered in seabed sediment – they kept a small piece of Earth’s ancient history alive in their fossil shells.
For decades, scientists have studied these shells and found traces of the ancient Earth̵
The new paper, which covers decades of deep-sea drilling emissions in a single record, describes the Earth’s climate fluctuates throughout Cenozoic era the 66 million year period that began with the death of dinosaurs and extends to the present era of human-induced climate change. The results show how the Earth shifted through four different climatic conditions – called the Heating House, Heating House, Cooling House and Ice House – in response to changes in the planet’s orbit, greenhouse gas levels and extent of the polar ice.
Related: 10 Signs of the Earth’s climate
The zig-zagging chart (shown above) ends with a sobering peak. According to researchers, the current pace is man-made global warming far exceeds the natural climate fluctuations seen at any other time in the Cenozoic era, and has the potential to hyper-propel our planet out of a long ice house phase into a burning greenhouse state.
“Now that we have succeeded in capturing natural climate variability, we can see that the expected man-made warming will be much greater than that,” studies co-author James Zachos, professor of earth and planetary science at the University of California, Santa Cruz. , said in a statement. “Intergovernmental Panel on Climate Change (IPCC) projections to 2300 in the “business-as-usual” scenario will potentially bring the global temperature to a level that the planet has not seen for 50 million years. “(The IPCC is a UN group that assesses the science, risks and effects of climate change on the planet.)
Into the greenhouse
To compile their new era-long climate map, the study authors examined fossil forehead shells in deep-sea sediment cores – long tubes of rock, sediment and microbes – drilled from the world’s oceans over the past several decades. Forams (short for foraminifera) are microscopic plankton whose oldest relatives appeared in the ocean nearly a billion years ago; the deeper scientists dig themselves into the ocean floor, the older the pre-samples they reveal.
Relationship between carbon and oxygen isotopes (versions of elements) in forehead shells contain critical climate information. The relationship between the oxygen isotopes oxygen-18 and oxygen-16 can e.g. Reveal how hot the surrounding water was when a foram constructed its shell; the higher the conditions, 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, scientists also had to consider astronomical influences on the planet’s climate – that is, how the Earth’s slowly changing orbit and tilt toward the sun affect the amount of sunlight reaching different parts of the planet at different times. known as Milankovitch bikes. As the team overlapped orbit data with their isotopic climate data, they saw that orbital variations created clear but relatively small changes in the global climate. What was crucial was that every major leap between climate states was tied to a massive shift in greenhouse gas levels, the researchers said.
For example, about 10 million years after the dinosaur extinction, the earth jumped from a greenhouse state to a greenhouse state. This event, known as the Paleocene-Eocene Thermal Maximum, saw temperatures up to 29 degrees Fahrenheit (16 degrees Celsius) above modern levels, Zachos said, and was driven by a massive release of carbon into the atmosphere, believed to be the result of huge volcanic eruptions in the North Atlantic. . Similarly, as carbon dioxide disappeared from the atmosphere over the next 20 million years, ice sheets began to form. Antarctica and the planet entered a cold store phase with surface temperatures averaging approx. 4 ° C above modern levels.
Related: 10 ways the earth changed forever in 2019
About 3 million years ago, Earth entered an ice house phase driven by growing and declining ice sheets in the northern hemisphere. Now, human greenhouse gas emissions are causing temperatures to rise to an extent not seen in tens of thousands of years. This increase is far beyond the natural variations triggered by the Earth’s changing orbit, the researchers concluded. And if current greenhouse gas emissions remain stable, the climate could skyrocket back to levels not seen since the Paleocene-Eocene Thermal Maximum. The transition from ice house to greenhouse does not take millions of years, Zachos said – it will take hundreds.
“We now know more precisely when it was warmer or colder on the planet and have a better understanding of the underlying dynamics and the processes that drive them,” says study author Thomas Westerhold, director of the University of Bremen Center for Marine Environmental Sciences in Germany , said in the statement. “The 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 man-made changes may lead to. “
Editor’s note: This story was updated on September 11th to correct two Celsius and Fahrenheit conversions.
Originally published on WordsSideKick.com.