“Scientists warn the sun will ‘go to sleep’ in 2030 and could cause temperatures to plummet,” blared one headline from this weekend.
“Earth heading for ‘mini ice age’ within 15 years,” warned another.
By Sunday evening, news that the Earth could be headed for period of bitter cold was trending on Facebook and whizzing across Twitter. The story – which has been reported everywhere from conservative blogs to the British press to the Weather Channel to the Huffington Post – was based on a recent presentation at the Royal Astronomical Society’s national meeting. Researchers studying sunspots found that solar activity is due to decline dramatically in the next few decades, reaching levels not seen since the 17th century, during a period known as the Maunder minimum. Back then, the decline coincided with what’s called the “Little Ice Age,” when Europe’s winters turned brutally cold, crops failed and rivers froze over.
Could another one be on its way?
Though University of Northumbria mathematics professor Valentina Zharkova, who led the sunspot research, did find that the magnetic waves that produce sunspots (which are associated with high levels of solar activity) are expected to counteract one another in an unusual way in the coming years, the press release about her research mentions nothing about how that will affect the Earth’s climate. Zharkova never even used the phrase “mini ice age.” Meanwhile, several other recent studies of a possible solar minimum have concluded that whatever climate effects the phenomenon may have will be dwarfed by the warming caused by greenhouse gas emissions.
Besides, that “Little Ice Age” that occurred during the Maunder minimum, it wasn’t so much a global ice age as a cold spell in Europe, and it may have been caused more by clouds of ash from volcanic eruptions than by fluctuations in solar activity.
(It’s also worth mentioning that Zharkova’s findings have not yet been published in a peer-reviewed journal, so her conclusions haven’t been vetted and refined.)
But those nuances were totally lost as stories about Zharkova’s research made the rounds on social media and in the press. Instead, we got 300-year-old engravings of Londoners cavorting on the frozen River Thames accompanied by predictions of food shortages and brutal cold – plus snarky tweets about not worrying about global warming anymore.
This isn’t the first time that a story about sunspots has turned into a story about climate change skepticism. John Casey, president of the Orlando-based Space and Science Research Corporation, which denies that global temperatures are rising, has written two books on the threat of impending “solar hibernation.” In 2011, when a series of studies concluded that the sun was heading into a cycle of unusually low activity, one headline cheered “Global Warming Be Damned, We Might Be Headed for a Mini Ice Age.”
For decades, scientists have known that solar activity fluctuates according to a roughly 11-year cycle. Sunspots – (relatively) cool, dark blotches on the sun’s surface – indicate areas of intense magnetic activity. But recently sunspots have been weakening, as has the sun’s magnetic field, leading scientists to conclude that the sun is heading into an especially quiet cycle termed the “grand solar minimum”
The new research from Zharkova argues that the solar cycles are regulated by not one but two magnetic waves fluctuating at slightly different frequencies, and that the unusually low activity can be explained by the waves getting far enough out of sync that they effectively cancel one another out.
Even if the upcoming decline in solar activity turns out to be as Zharkova’s suggests, scientists who study the sun say we can’t be sure how it will affect Earth’s climate.
“We have some interesting hints that solar activity is associated with climate, but we don’t understand the association,” Dean Pesnell, a NASA scientist who worked on one of the 2011 studies about the grand minimum, told National Geographic at the time.
Those studies that have found a correlation between solar activity and global temperatures predict that the drop in temperatures associated with a grand minimum will be much smaller than the warming that’s predicted to occur due to greenhouse gas emissions: A 2010 study in the journal Geophysical Letters predicted it could cause a global temperature decrease of about 0.3 degrees Celsius by 2100 – not nearly enough to offset the 1 to 5 degree increase anticipated from human-caused global warming.
As for that image of Londoners frolicking at “frost fairs” on the frozen-over Thames? Those had less to do with the activity of the sun than the activities of humans. Historical climatologist George Adamson told the BBC last year that the river used to freeze because of the architecture of the old London Bridge, whose arches prevented salty sea water from passing upriver and lowering its freezing point. The construction of a new bridge in the 19th century, and other landscape changes that made the river flow faster, brought an end to those festivals – less so than the end of the Maunder minimum.
“I’d be surprised if it froze again to the extent where we’d be able to allow large numbers of people on the Thames,” he said.
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