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Back in the Jurassic period, we know things were quite different here on Earth. Dinosaurs roamed Laurasia and Gondwana, sea monsters like plesiosaurs swam the oceans, and teeming jungles covered hills and plains. The global climate was almost certainly hotter and more humid, too. But by how much? Until now, we had an idea, but we couldn’t really say with much accuracy. Existing climate records grow hazy beyond 800,000 years.

A new technique may change that, though. By studying the composition of zooplankton fossils, paleoclimatologists at the University of Cambridge have dramatically extended the climate record.

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Fossilized, prehistoric ancestors of zooplankton like this specimen are helping to extend climate records.

Scientific American:

The shells preserve information about the conditions in the oceans by continuously picking up sediments on the seafloor and trapping the material within their mineral makeups. The researchers measured their mineral composition using scanning transmission x-ray microscopy, a method originally developed for looking at manufactured products such as microstructures in hard drives.

Different elements present in the fossilized structures provide snapshots of climate variations up to 200 million years ago. Magnesium records daily fluctuations, boron documents changes in pH. It’s a powerful new tool that could help us learn how some of the most abundant organisms on Earth might react to a warming climate and acidifying oceans.