International
via The International Ocean Discovery Program

World - 66 Million Years of Earth's Climate Uncovered From Ocean Sediments

Changes in the Earth’s climate over the last 66 million years have been revealed in unprecedented detail , highlighting four distinctive climatic states and the natural million- and thousand-year variability that Earth’s climate has experienced.

Published today in Science, the new global “climate reference curve” created by the team is the first record to continually and accurately trace how the Earth’s climate has changed since the great extinction of the dinosaurs 66 million years ago.

It was achieved by bringing together research from 12 international laboratories using sample material from the ocean floor collected over more than five decades of international scientific drilling expeditions by the International Ocean Discovery Program (IODP) and its predecessors.

Led by researchers from MARUM – Center for Marine Environmental Sciences at the University of Bremen, the Potsdam Institute for Climate Impact Research (PIK) and UCL, the authors used advanced mathematical analysis of this highly accurate climate reference curve to identify four climatic states, classified as “Hothouse”, “Warmhouse”, “Coolhouse” and “Icehouse”. These states are recognised by the characteristic pattern of their climate variability. The distinctive climatic “beat’ of each state is driven by greenhouse gas concentrations and polar ice volume, with higher CO2 and little-to-no global ice volume during the Hothouse and Warmhouse compared to the Coolhouse and Icehouse.

To generate the climate reference curve, called CENOGRID (CENOzoic Global Reference benthic foraminifer carbon and oxygen Isotope Dataset), the team analysed and compiled the oxygen and carbon isotopes from tiny microfossils found in deep-sea sediments. For the first time, this period of Earth’s history was accurately dated by identifying the imprint of semi-periodical changes in Earth’s orbit around the sun in CENOGRID.

The CENOGRID is the clearest and most accurate view of past climate conditions to date, providing information about past deep-sea temperatures, global ice volumes and the carbon cycle. These detailed climatic changes can be studied like a colourful barcode and used to draw comparisons between the past, present and future.

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