For hundreds of years scientists have used the number of observable sunspots to trace the sun's roughly 11-year cycles of activity.
Sunspots, which can be visible without a telescope, are dark regions that indicate intense magnetic activity on the sun's surface. Such solar storms send bursts of charged particles hurtling toward Earth that can spark auroras, disrupt satellites, and even knock out electrical grids.
In the current cycle, 2008 was supposed to have been the low point, and this year the sunspot numbers should have begun to climb.
But of the first 90 days of 2009, 78 have been sunspot free. Researchers also say the sun is the dimmest it's been in a hundred years.
The Maunder Minimum corresponded to a profound lull in sunspots—astronomers at the time recorded just 50 in a 30-year period.
If the sun again sinks into a similar depression, at least one preliminary model has suggested that cool spots could crop up in regions of Europe, the United States, and Siberia.
During the previous event, though, many parts of the world were not affected at all, said Jeffrey Hall, an astronomer and associate director at Lowell Observatory in Flagstaff, Arizona.
"Even a grand minimum like that was not having a global effect," he said.
Wild Cards and Uncertainties
Changes in the sun's activity can affect Earth in other ways, too.
For example, ultraviolet (UV) light from the sun is not bottoming out the same way it did during the past few visual minima.
"The visible light doesn't vary that much, but UV varies 20 percent, [and] x-rays can vary by a factor of ten," Hall said. "What we don't understand so well is the impact of that differing spectral irradiance."
Solar UV light, for example, affects mostly the upper layers of Earth's atmosphere, where the effects are not as noticeable to humans. But some researchers suspect those effects could trickle down into the lower layers, where weather happens.
In general, recent research has been building a case that the sun has a slightly bigger influence on Earth's climate than most theories have predicted.
Atmospheric wild cards, such as UV radiation, could be part of the explanation, said the University of Southampton's Lockwood.
In the meantime, he and other experts caution against relying on future solar lulls to help mitigate global warming.
"There are many uncertainties," said Jose Abreu, a doctoral candidate at the Swiss government's research institute Eawag.
"We don't know the sensitivity of the climate to changes in solar intensity. In my opinion, I wouldn't play with things I don't know."
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