Solar Activity Linked to Natural Climate Change in Europe

Changes in the Sun's activity have led to natural climate changes in Europe over the past 1,000 years, according a new study.

Writing in the journal Nature Geosciences, researchers from University of Cardiff and University of Bern report that that the slight changes in heat in the North Atlantic Ocean have led to regional climate variability across centuries and can be linked to severe winter weather events in the 16th and 18th centuries.

"We used seafloor sediments taken from south of Iceland to study changes in the warm surface ocean current. This was done by analyzing the chemical composition of fossilized microorganisms that had once lived in the surface of the ocean," said lead study author Paola Moffa-Sanchez, from Cardiff University School of Earth and Ocean Sciences. "These measurements were then used to reconstruct the seawater temperature and the salinity of this key ocean current over the past 1,000 years."

The analyses revealed large and abrupt changed in salinity and temperature in the warm currents of the North Atlantic that have occurred on time scales of several decades, up to several centuries.

During periods of recorded low solar energy output, measured by intervals of low sunspot activity on the Sun, the researchers found cold ocean conditions.

"By using the climate model it was also possible to explore how the changes in solar output affected the surface circulation of the Atlantic Ocean," said study co-author Ian Hall. "The circulation of the surface of the Atlantic Ocean is typically tightly linked to changes in the wind patterns. Analysis of the atmosphere component in the climate model revealed that during periods of solar minima there was a high-pressure system located west of the British Isles. This feature is often referred to as atmospheric blocking, and it is called this because it blocks the warm westerly winds diverting them and allowing cold Arctic air to flow south bringing harsh winters to Europe, such as those recently experienced in 2010 and 2013."

Various meteorological studies over the past several decades have led researchers to believe the Earth's upper atmospheric layer, the stratosphere, has something to do with the strength of atmosphere winter blockings.

"In this study we show that this relationship is also at play on longer time-scales and the large ocean changes, recorded in the microfossils, may have helped sustain this atmospheric pattern," said Moffa-Sanchez. "Indeed we propose that this combined ocean-atmospheric response to solar output minima may help explain the notoriously severe winters experienced across Europe between the 16th and 18th centuries, so vividly depicted in many paintings, including those of the famous London Frost Fairs on the River Thames, but also leading to extensive crop failures and famine as corroborated in the record of wheat prices during these periods."

The researchers noted, however, that any future climate change due to solar activity will be much smaller than the warming that will occur from human carbon dioxide emissions.