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Monday, September 1, 2008

Sun Makes History: First Spotless Month in a Century

Full story (here).
The sun has reached a milestone not seen for nearly 100 years: an entire month has passed without a single visible sunspot being noted.

The event is significant as many climatologists now believe solar magnetic activity – which determines the number of sunspots -- is an influencing factor for climate on earth.

According to data from Mount Wilson Observatory, UCLA, more than an entire month has passed without a spot. The last time such an event occurred was June of 1913. Sunspot data has been collected since 1749.

When the sun is active, it's not uncommon to see sunspot numbers of 100 or more in a single month. Every 11 years, activity slows, and numbers briefly drop to near-zero. Normally sunspots return very quickly, as a new cycle begins.

But this year -- which corresponds to the start of Solar Cycle 24 -- has been extraordinarily long and quiet, with the first seven months averaging a sunspot number of only 3. August followed with none at all. The astonishing rapid drop of the past year has defied predictions, and caught nearly all astronomers by surprise.

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In the past 1000 years, three previous such events -- the Dalton, Maunder, and Spörer Minimums, have all led to rapid cooling. One was large enough to be called a "mini ice age". For a society dependent on agriculture, cold is more damaging than heat. The growing season shortens, yields drop, and the occurrence of crop-destroying frosts increases.

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