Climate change reference curve spanning 66 mn years made using ocean sediments

The reconstruction and analysis show that Earth's climate can be grouped into discrete states, based on changing greenhouse gas levels and growth of polar ice sheets.

Researchers have revealed in intricate details the changes in the Earth's climate over the last 66 million years. The team highlighted four distinctive climatic states and the natural million-and thousand-year variability that Earth's climate has experienced.

The new global 'climate reference curve' was created by a team of researchers from 12 international laboratories and is the first record to trace how Earth's climate has changed since the extinction of dinosaurs 66 million years ago.

The research was led by scientists from MARUM — Center for Marine Environmental Sciences at the University of Bremen, the Potsdam Institute for Climate Impact Research (PIK) and UCL.

In a statement issued by the Potsdam Institute for Climate Impact Research (PIK), researchers revealed that they compiled and analysed a comprehensive dataset obtained from sediment cores from the ocean floor to obtain the results.

First author Thomas Westerhold of MARUM explained that the goal was to create a new reference of past climate over the last 66 million years. “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," Westerhold added.

Norbert Marwan of PIK went on to reveal that their mathematical analyses revealed the hidden relationships and recurring patterns in the climate, adding that they can learn something about the "rapid anthropogenic changes of our present century from the slow natural climate fluctuations occurring over millions of years."

The study authors with the help of advanced mathematical analysis identified four climatic states, classified as “Hothouse,” “Warmhouse,” “Coolhouse,” and “Icehouse.” Each state is recognised by the characteristic pattern of climate variability and the distinctive climactic 'beat' of each state is driven by greenhouse gas concentrations and polar ice volume, with higher CO2 and almost no global ice volume during the Hothouse and Warmhouse compared to Coolhouse and Icehouse.

The new climate reference curve has been named CENOGRID (CENOzoic Global Reference benthic foraminifer carbon and oxygen Isotope Dataset). It is a reconstruction of the Earth’s climate since the last great extinction 66 million years ago, which introduced a new Era, the Cenozoic.

According to Marwan, this kind of analysis also makes it possible to draw inferences about the probability of events, provided there is a large amount of data and long data series.

In future, the new climate reference curve CENOGRID can serve as a basis for researchers around the world to accurately correlate their data within the context of climate history.

The results of the study have been published in the journal Science.

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