Fossil shells tell us that the climate warms more in summer than in winter

Hearing that the world’s temperature will rise by three degrees does not mean much to many people. This sounds like the ability to spend more days in a bikini and less slippery roads in the winter, if you look at it optimistically. Of course, averages don’t tell us much about what a particular place might be like, what extreme weather conditions lie ahead, or in which season rising temperatures will have the greatest impact.

Belgian, Dutch, German and British researchers have now found an answer to the last question in fossil shells from the North Sea: Summer temperatures are much warmer than winters in a warmer climate. While winter was 2.5 degrees warmer, summer temperatures were 4.3 degrees warmer.

According to scientists, the study provides a picture of the climate we can expect in Europe by 2100 if the current trend of climate change continues. “There will likely be greater temperature differences between summer and winter, and the chance of heatwaves in summer will increase,” said Niels de Winter, a researcher at VUB.

Heavy isotopes

Oyster, clam and mussel shells have the property of increasing in size layer by layer as the animal inside grows. The chemical composition of the layers therefore reflects the changing chemistry of the environment over time. The researchers analyzed the presence of rare heavy isotopes of oxygen and carbon in lime particles found in the shells.

These heavy isotopes (same chemical element, but with more protons in the nucleus) are more common in shells grown in cold water. The isotope content therefore reflects the temperature of the water at the formation of a particular layer of crust. Because the method does not use chemical elements that depend on the composition of seawater, it is more accurate in determining temperature than other analyses.