In 1610, shortly after viewing the sun with his new telescope, Galileo Galilei (or was it Thomas Harriot?) made the first European observations of Sunspots. Continuous daily observations were started at the Zurich Observatory in 1849 and earlier observations have been used to extend the records back to 1610. The sunspot number is calculated by first counting the number of sunspot groups and then the number of individual sunspots.
|The "sunspot number" is then given by the sum of the number of individual sunspots and ten times the number of groups. Since most sunspot groups have, on average, about ten spots, this formula for counting sunspots gives reliable numbers even when the observing conditions are less than ideal and small spots are hard to see. Monthly averages (updated monthly) of the sunspot numbers (181 kb JPEG image), (307 kb pdf-file), (62 kb text file) show that the number of sunspots visible on the sun waxes and wanes with an approximate 11-year cycle.|
Environmental Consultant Edmund Contoski, writing for the Heartland blog, says that The Sun, Not CO2, Determines our Climate.
The chart [above] clearly shows a weakening trend of sunspots in solar cycles 22, 23 and 24. These are the latest in a sequence dating from 1755, when extensive recording of solar sunspot activity began. Note that the peak of solar cycle 24, which occurred in 2014, is only about half that of solar cycle 22, which peaked about 1989.
This portends global cooling—not global warming. Sunspots are dwindling to lows not seen in 200 years. In 2008, during the solar minimum of cycle 23, there were 266 days with no sunspots. This is considered a very deep solar minimum. You can check out pictures of sunspots—or their absence—day after day for recent years at http://tinyurl.com/6zck4x. (Source - bold added)
After explaining Sunspot activity, Edmund Contoski continues
After about 210 years, sunspot cycles “crash” or almost entirely die out, and the earth can cool dramatically. These unusually cold periods last several decades. Of greatest concern to us is the Maunder Minimum, which ran from 1645 to 1715. Below is a chart that shows the paucity of sunspots during this time. Some years had no sunspots at all.
The astronomer Sporer reported only 50 sunspots during a 30-year period, compared to 40,000 to 50,000 typical for that length of time.
Since the Maunder Minimum, a less extreme but still significantly below-average period of cooler temperatures occurred during the Dalton Minimum (1790 to 1830), also shown on the graph.
At least as far back as 2007—before Cycle 23 had bottomed—a Russian solar physicist, predicted what we are seeing now. Professor Habibullo Abdussamatov, head of the Pulkovo Observatory in Russia, noting that solar irradiance had already begun to fall, said a slow decline in temperatures would begin as early as 2012-2015 and lead to a deep freeze in 2050-2060 that will last about fifty years.Read More HERE