It was Galileo, using his newly invented telescope, who, around 1600, saw sunspots for the first time in western history. From that point forward, sunspot observations were made on a regular basis by astronomers throughout Europe.
Sunspot observations had also been made by the Chinese around 800 AD.
In 1800, an astronomer, Herschel, was struck by the eleven-year sunspot cycle, and the perceived variation in commerce every ten years. Turning to Adam Smith’s Wealth of Nations, he found data about the price of wheat that varied with the sunspot cycle. When sunspots were few in number, the price of wheat was high, and when sunspots were plentiful, there were abundant harvests and the price of wheat was low.
With this rudimentary idea that sunspots were related to climate, other astronomers, often sustaining criticism from their peers, searched for more data that could establish a stronger link between sunspots and climate.
Dramatic evidence of a strong linkage was provided by another astronomer, Walter Maunder, who at the age of 70, in 1922, linked the lack of sunspots between 1645 and 1715, to the bitter cold of that period.
It wasn’t until the 1970s, when Dr. Jack Eddy focused attention on Maunder’s work, that the significance of the Maunder Minimum became understood.
The Maunder Minimum is believed to have been the cause of the Little Ice Age. The Dalton Minimum is the period during the first two cycles beginning around 1800.
The 20th century seems to have been a period where sunspots were more frequent, especially from 1950 to 2000, while the most recent cycles in the 21st century have had fewer sunspots.
The forecast is for cycle 25 to be smaller in number than cycle 24, shown to the right of this photo, which is the smallest number of sunspots since cycle 14 that reached its peak around 1912.
Even if there is a causal relationship between sunspots and climate, it has only been recently that a mechanism for the linkage has been proposed.
In 1997, Dr. Svensmark, a Danish scientist at the Danish National Space Institute, proposed that sunspot eruptions affected the strength of the sun’s magnetic field, which in turn, affected the earth’s magnetic field.
When the magnetic fields surrounding the earth were strong, during periods of high sunspot activity, cosmic rays were deflected away from the earth. When there were few sunspots, during periods of low sunspot activity, cosmic rays could enter the earth’s atmosphere and affect the earth’s climate.
Svensmark suggested that cosmic rays could affect low level cloud formation, with more cosmic rays creating more low level clouds. He proposed that an increase in low level cloud coverage would result in lower temperatures as they acted like a shade over the earth, while also reflecting more sunlight away from the earth’s surface.
The major controversy surrounding Svensmark’s hypothesis was whether cosmic rays could induce cloud formation.
In 2007, Svensmark conducted a laboratory experiment that seemed to confirm that cosmic rays could induce cloud formation.
The debate then resulted in the Cloud experiment at CERN, Europe’s premiere research center.
The Cloud experiment proved, with little doubt, that cosmic rays can induce cloud formation.
Professor Nir Shaviv, Hebrew University, Jerusalem, explains all of this, plus the results of computer projections using the effects of low level clouds on temperatures, in a 37 minute presentation. The presentation is available at http://www.youtube.com/watch?v=8QtnueIJGjc
Svensmark has provided an explanation for how the sun, or more specifically sunspots, can affect climate change.
While this is admittedly only a hypothesis, it has substantial scientific underpinning going back several hundred years, and perhaps longer.
This is in contrast with the CO2 hypothesis that’s based on data going back only a hundred years or so.
In addition, the sunspot hypothesis is consistent for hundreds of years, at least back to 1600, while the data supporting the CO2 hypothesis is not consistent.
From the mid 1800s throughout the 20th century, temperatures increased as atmospheric CO2 increased, but prior to 1860 atmospheric CO2 remained virtually constant while temperatures varied, up and down, including the medieval warm period and the little ice age.
If temperatures varied while atmospheric CO2 remained constant, there must not have been a very strong linkage between temperatures and atmospheric levels of CO2.
The Carrington event demonstrated the power of the sun, while Svensmark has shown how its power could affect climate change.
Couldn’t the sun be a more reasonable answer for climate change than atmospheric CO2?
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