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.
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.
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.
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.