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Researchers have analyzed data from deep-sea deposits in order to reconstruct Earth’s climate with an unprecedented temporal resolution. To achieve this, an international team, among them prof Lucas Lourens of Utrecht ľ�ϸ���Ӱ�� compiled and analyzed a comprehensive dataset obtained from sediment cores from the ocean floor. The team’s new climate reference curve is published in the prestigious professional journal .

“Our goal was to create a new reference of past climate over the last 66 million years, which not only incorporates the highest-resolution data but is also more accurately dated,” explains first author Thomas Westerhold. “We now know more accurately when it was warmer or colder on the planet and we also have a better understanding of the underlying dynamics.”

The view into the past is also a glimpse into the future. We can learn something about the staggeringly rapid anthropogenic changes of our present century from the slow natural climate fluctuations occurring over millions of years. The climatic changes of the past 66 million years can be studied like a colorful barcode.

Layers of sediment on the ocean floor have been explored by the scientific drill ship JOIDES Resolution across the world for more than five decades through internationally coordinated expeditions. By studying these sediments and the microfossils within, scientists are able to reconstruct and analyze global climate changes into the distant past.

They examine the evidence preserved in oxygen and carbon isotopes, which provides information about the past deep-sea temperatures, global ice volumes and the carbon cycle. These clues are stored in the shells of microorganisms that once lived on the sea floor. They represent an archive of past climate conditions that researchers use to draw comparisons between the past, present and future.

“I was a scientific participant in one of the key expeditions, now 18 years ago,” says prof Lucas Lourens. “The data coverage older than 34 million years was generally poor. Over the past two decades, scientific drilling programs have targeted their drilling into older geological strata. We have a more complete sediment archive now, and are able to reconstruct global climate in much more detail than ever before.”

The new climate reference curve, called CENOGRID (CENOzoic Global Reference benthic foraminifer carbon and oxygen Isotope Dataset), is a reconstruction of the Earth’s climate since the last great extinction 66 million years ago, which introduced a new Era, the Cenozoic. It is a tremendous joint effort by many colleagues internationally to recover the sample material, analyze it and compile it into an integrated curve.

The data and age models of CENOGRID have been radically improved to understand what climate conditions existed in the past, what processes lay behind them, and how they proceeded. There were four predominant climatic modes in the Cenozoic – hothouse, warmhouse, coolhouse and icehouse. The long time span of 66 million years is advantageous for various reasons, because only then can be investigated whether climatic events or patterns recur and are therefore determined by natural processes. Or whether they are anomalous and therefore a cause for concern.

CENOGRID can serve as a basis for researchers worldwide to accurately correlate their data within the context of climate history. With more data, it is now possible to not only further refine the picture of the climatic past, but also to identify regional intricacies. The authors emphasize that this is fundamental for testing the reliability of climate models for the future.

Publication: Westerhold et al. 2020. An astronomically dated record of Earth’s climate and its predictability over the last 66 Million Years. Science 2020. DOI: 10.1126/science.aba6853.