Some astronomers call it the Big Quiet – the absence of sunspots during what is supposed to be a period of heightened magnetic activity on our sun.
For past four or more days, telescopes pointed at the sun have detected only a handful of sunspots, sometimes none at all, in a “very weird” development that is baffling scientists, said Alan Duffy, an astrophysicist at Swinburne University.
“Sunspots can change all the time, but when you should be seeing many dozens at any one point of time, it’s quite strange that we’re not seeing any at all,” Dr Duffy said. “We don’t have any idea why that is.”
Active sunspots. Photo: NASA
Sunspots have been studied for centuries and are one gauge of the solar cycle – a roughly 11-year period of above- or below-average magnetic activity. During maximum periods, such as the current one, observations of sunspots and solar flares being fired by the sun should be more common.
Viewers of the World Cup, for instance, would have been grateful for the relative lack of interference of energetic bursts of radiation normally associated with solar-maximum periods that can force satellites to shut down and interfere with other electronics, Dr Duffy said.
Less fortunate, though, are tourists who have headed to the Arctic Circle to view the usually spectacular northern lights, or Aurora Borealis. “If you’ve got to the North Pole on one of these staggeringly expensive trips to see the northern lights, you’ll be really feeling cheated because there’ll be nothing for a while,” Dr Duffy said.
Lighting up - the Aurora Borealis. Photo: NASA
Climate link?
Scientists have been studying the effect of the relatively weak period of solar radiation for possible effects on the Earth’s climate for decades.
While global warming hasn't ceased, a waner sun has contributed on the margin to a flattening of recent surface temperature readings. (See a separate report about the role of the oceans, particularly during El Nino cycles.)
Aurora Borealis on a good night. Photo: NASA
The latest report of the United Nations Intergovernmental Panel on Climate Change noted “there are indications the mean magnetic field in sunspots may be diminishing on (a) decadal level”, but added the decrease in solar activity “will be much smaller in magnitude than the projected increased forcing due to greenhouse gases”.
Michael Ashley, a physics professor at the University of NSW, said weaker solar activity in past decades had contributed to a cooling of the planet of about 0.1-0.2 degrees. “To counteract global warming you’d need 10 times that,” he said.
“What is more worrying is if (the sun) warms up to its long-term average, then we’re going be a lot worse off,” Professor Ashley said.
Interest in the role of the sun in driving climate change picked particularly after the 1960s when researchers identified the so-called Maunder Minimum of low sunspot activity between about 1645 and 1715.
That period coincided with the so-called Little Ice Age when Europe especially experienced a drop in temperatures of about half a degree compared with the start of the 20th century, according to Steve Sherwood, a professor specialising in atmospheric climate dynamics, also at the UNSW.
In recent years, though, scientists have begun to downplay the role of the sun in shifting climates, viewing volcanic activity, ocean current changes and other factors playing important parts.
The Maunder Minimum, for instance, was about 50-60 years in the middle of the Little Ice Age but the cool period extended “a lot longer either side...so it couldn’t have just been the sun”, Professor Ashley said.
The solar cycle “does have an impact but it’s overwhelmed by the greenhouse-gas effect,” he said, referring to emissions produced by humans burning fossil fuels and clearing land.