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Chilly European winters linked to solar activity


August 27, 2012

The frozen Rhine river close to Mainz during the winter of 1962/1963 (Photo: Frank Sirocko)

The frozen Rhine river close to Mainz during the winter of 1962/1963 (Photo: Frank Sirocko)

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Some clever cross-referencing has helped an international team of researchers establish a link between low periods of solar activity and frosty European winters. The Sun's level of magnetic activity follows an 11-year cycle. Peaks in this cycle pose a threat to telecommunications and electricity networks and it's long been suspected that there's a correlation between the opposite end of the cycle and extreme winters in Europe. A lack of historical average temperature data makes it difficult to confirm this link, but scientists have filled the gap by studying the comings and goings of 19th Century riverboats on the Rhine.

Average temperature records may not have been kept 200 years ago, but records of riverboat traffic on the Rhine were. When the river froze, the boating stopped.

Professor Dr. Frank Sirocko hit upon the idea of using proxy data on freezing rivers to trace patterns in solar activity when he attended a once 25-mile ice-skating race in the Netherlands that can only be held every decade or so during extremely cold winters.

Evidence of a river freezing makes for a simple yardstick: "Either there is ice or there is no ice," says Sirocko.

The Rhine is a big river, so when it freezes it's a solid indication that it's very cold.

Comparing boating records from 1780 to 1963 with the 11-year Solar cycle, the team found that ten of the fourteen big freezes in the region occurred during years of low solar activity. The scientists say this adds-up to a 99 percent chance that extremely cold winters in central Europe and low solar activity are linked.

"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," says Sirocko.

The study adds to our knowledge of the role solar activity plays in the Earth's climate system, but the regional nature of the data and the complex interplay between this and other weather factors means it's only part of the puzzle.

"There is some suspension of belief in this link," according to Thomas Crowley, Director of the Scottish Alliance for Geoscience, Environment, and Society. "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."

"Climate is not ruled by one variable," says Sirocko. "In fact, it has at least five or six variables. Carbon dioxide is certainly one, but solar activity is also one."

The paper entitled Solar influence on winter severity in central Europe is published in the journal Geophysical Research Letters.

Source: Johannes Gutenberg-University Mainz

About the Author
Noel McKeegan After a misspent youth at law school, Noel began to dabble in tech research, writing and things with wheels that go fast. This bus dropped him at the door of a freshly sprouted Gizmag.com in 2002. He has been Gizmag's Editor-in-Chief since 2007. All articles by Noel McKeegan

This does not come as a surprise to AGW deniers.


I wonder if some correlation could be made for warm summers, perhaps if there is data regarding the amount of ice sold/available for iceboxes (at least in the pre-refrigerator era). More ice sold, hotter summer? An interesting piece nonetheless. Extra variables can be so inconvenient.

Bruce H. Anderson

Science confirms good old farmer's knowledge. When I was growing up in the South of France, local farmers would say the climate goes in cycles of 30 years, hot to cold to hot. Nice to see science is confirming something they've always observed :)

Nicolas Zart

Exactly what AGW skeptics have been saying for a long time. Look up the Maunder Minimum. That was a period of very low sunspot activity which matches up with much of the period of time known as the Little Ice Age.

Sunspot observations before that time were more, uh, spotty, but the records available indicate a higher than average amount of them during the warm period prior to the LIA.

The global warming people, especially the AGW ones, like to point out that the percentage of change in solar output from peak to trough of the cycle is quite small.

They never mention that the total amount of energy variance from that small percentage is extremely huge. Earth catches a lot of terawatts of solar energy, which is just a tiny fraction of the yottawats of total solar output.

Something else to consider is Hurricane Katrina unleashed an estimated 500 terawatts in its 7 days at category 5. That's around 15 years worth of the total energy use of the entire human race.

Where did Katrina get all that power? THE SUN. Every second enough solar energy smacks Earth to power dozens of Katrina sized hurricanes.

Everything humans can do is practically zero next to the total mount of energy output variance the Sun undergoes in its sunspot cycle.

When you use the actual, gigantic numbers instead of trying to minimize Solar effects by using percentages, one can easily see that yes indeed the Sun is the most powerful influence on Earth's climate.

Gregg Eshelman

This does not come as a surprise to AGW supporters (ie: rational humans) either.


"Climate is not ruled by one variable," says Sirocko. "In fact, it has at least five or six variables. Carbon dioxide is certainly one, but solar activity is also one."

My understanding is that the variation in solar activity was always built into the equations for understanding climate change. This finding merely tends to confirm.

Showing that solar activity actually can cause climate change does not negate the other factors in any way. Human activity still has a high probability of being one of these causes, and as such we should try to limit our effect.


2500 Years of European Climate Variability and Human Susceptibility Climate variations influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution paleoclimatic evidence. We present tree ring–based reconstructions of central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~250 to 600 C.E. coincided with the demise of the western Roman Empire and the turmoil of the Migration Period. Such historical data may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change. http://www.sciencemag.org/content/331/6017/578.abstract

Wim Streep

re; Wim Streep

And then there was the Medieval Warm Period when the population of Europe soared with the increased food production to the point they had food and population to build cathedrals, and colonizing Greenland looked like a good idea. The evidence is that it was warmer then than they are predicting that it will be now.

Thermometers have not been invented long enough to call current warming to be at an unprecedented rates.


re; Wim Streep

Strange how the same climate disruptions didn't bring down the Eastern Roman Empire, but they had more competent leadership which included an army that for the most part still operated as a meritocracy. The Western Roman Empire of the time was made up of undisciplined barbarians under the nominal command of neerdowell relations of the Emperor sent to the borders to keep them from being an embarrassment in Rome.

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