Cold European Winters Due to Low Solar Activity

A new study published in the Geophysical Research Letters trace a link between the cold European winters and solar activity. In the initial period the scientists blamed the Sun's 11 year cycle that altered the climate in certain region on Earth. But they lacked data to validate the changing pattern.  

But recently the researchers at Johannes Gutenberg and the Institute for Atmospheric and Climate Science in Zurich, Switzerland, claimed that usually cold winters in Central Europe are related to low solar activity, when the sunspots numbers are low. The key to this is the freezing of Germany's largest river, the Rhine.

According to the release, "The new analysis has revealed a correlation between periods of low activity of the Sun and of some cooling - on a limited, regional scale in Central Europe, along the Rhine."

"The advantage with studying the Rhine is because it's a very simple measurement," said Frank Sirocko lead author of a paper on the study and professor of Sedimentology and Paleoclimatology at the Institute of Geosciences of Johannes Gutenberg University in Mainz, Germany. "Freezing is special in that it's like an on-off mode. Either there is ice or there is no ice."

It was noticed by Sirocko and his colleagues that between 1780 and 1963 the Rhine that was used for cargo transport froze in multiple places for nearly fourteen times. They then tracked the freezing episodes with the 11 year cycle of the sun, the determined that ten of the fourteen freezes occurred during years when the Sun had minimal sunspots.

They suspect that this is the prime reason for the Central European winters.

"We provide, for the first time, statistically robust evidence that the succession of cold winters during the last 230 years in Central Europe has a common cause," Sirocko said.

Thomas Crowley, Director of the Scottish Alliance for Geoscience, Environment, and Society, who was not involved with the study said, "There is some suspension of belief in this link," Crowley said, "and this study tilts the argument more towards thinking there really is something to this link. If you have more statistical evidence to support this explanation, one is more likely to say it's true."

It is learn that when the sunspot numbers are down, the Sun emits less ultraviolet radiation. Less radiation means less heating of Earth's atmosphere, which sparks a change in the circulation patterns of the two lowest atmospheric levels, the troposphere and stratosphere.

"Due to this indirect effect, the solar cycle does not impact hemispherically averaged temperatures, but only leads to regional temperature anomalies," said Stephan Pfahl, a co-author of the study who is now at the Institute for Atmospheric and Climate Science in Zurich.

According to the release, "the studies have suggested that the extremely cold European winters of 2010 and 2011 were the result of the North Atlantic Oscillation, which Sirocko and his team now link to the low solar activity during that time."