For a new study, published in the journal "Science", researchers have compiled the climate history of the past 66 million years. For this purpose, the team led by Thomas Westerhold from the Centre for Marine Environmental Sciences (Marum) at the University of Bremen and Norbert Marwan from the Potsdam Institute for Climate Impact Research (PIK) analysed ocean sediments. The results show how unprecedented the current global warming is.
The scientists drilled samples from the seabed of various oceans from a research vessel. They were particularly interested in the fossil shells of so-called foraminifers - tiny organisms living on the sea floor - which are embedded in the sediments. They then analysed their oxygen and carbon isotopes. These allow conclusions to be drawn about deep-sea temperatures, ice volume and carbon concentrations in the atmosphere at the time.
The resulting climate reference curve goes back to the mass extinction of 66 million years ago at the end of the Cretaceous period, which killed dinosaurs, among others. This was the beginning of the Cenozoic era, which continues to this day.
The two dozen or so researchers from six countries derive four basic climatic states from the climate curve: they call them
• and Icehouse
Science: An astronomically dated record of Earth’s climate and its predictability over the last 66 million years