How has the climate on the surface of our planet evolved over the past 4.5 million years, when the concentration of carbon dioxide in the air was of the same order of magnitude as today and the temperature on the Earth's surface was on average 3°C higher than today?
Global cooling indeed masks significant variations on the Earth's surface.
An article published in
Science
this Thursday, February 22, attempts to retrace this evolution.
The researchers used many indirect measurements of temperature.
They used the concentration of two oxygen isotopes found in fossils of foraminifera, widespread microorganisms with carbonate shells that lived on the ocean floor.
This made it possible to deduce the temperature of the seabed, then that of the ocean surface, and finally the average temperature on Earth.
This “paleo-thermometer” provides information on both the water temperature and the quantity of ice.
Global cold snap
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