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Dripstone cave (symbolic image)

Photo: Antonis Nikolopoulos / Eurokinissi / ANE Edition / IMAGO

Using stalactites and data from tree ring archives, climate fluctuations can be researched over periods of several centuries.

Geoscientists from Heidelberg University and the Karlsruhe Institute of Technology came to this conclusion in an analysis in the journal “Earth and Planetary Science Letters”.

The specialist team analyzed isotopes of oxygen in a stalactite in the Little Devil's Cave in Franconian Switzerland, i.e. versions of the oxygen atoms that have minimally different weights.

The oxygen isotopes get into stalactites with the water and provide information about the humidity and temperature of the air in times gone by.

The experts compared the information from the stalagmite, a stalactite growing out of the ground, with data from tree rings - trees also store oxygen isotopes from water (you can read more about this here).

The team reconstructed short-term climate fluctuations over the past centuries and related them to historically documented environmental events.

“Year without a summer” reconstructed

According to the team, the climate data obtained from the stalactites of the Little Devil's Cave reveal regional and global environmental events.

For example, the unusually cold year of 1816, which went down in history in Europe and North America as the “year without a summer”.

It was shaped by an eruption of the Tambora volcano in Indonesia in April 1815, possibly reinforced by another previously unknown volcanic eruption six years earlier.

The stalactite analyzes show that there were cold summers and rainy winters during this time.

They were associated with year-round floods, which led to crop failures and famine.

Long-term climate fluctuations can also be found in the data: for example, the so-called Little Ice Age, the core period of which began at the end of the 16th century and lasted until the late 17th century.

According to the specialist team, this time was characterized by frequent floods, which are historically documented for the city of Nuremberg, which is not far from the Devil's Cave.

The experts verified the climate data from the cave using a tree ring archive from the area.

They point to cold, dry winters during the Little Ice Age - which delayed the annual melting of ice and snow and, according to the scientists, probably led to severe short-term flooding.

Lime stones

Until now, short-term climate fluctuations over periods of several hundred years could usually only be analyzed using tree ring archives.

Cave stalactites made of lime, on the other hand, were only used in exceptional cases for the systematic measurement of climate data and their annual variations.

What is crucial for analyzes such as those that have now taken place is the rainwater that penetrates into a cave, the dissolved lime of which sometimes forms the stalactites over thousands of years.

This water from the environment consists of precipitation from the warm and cold seasons, each of which is characterized by a particular isotope composition of oxygen.

From this it can be deduced whether and in which years winter or summer precipitation dominated.

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