The Missing Sunspots: Is This the Big Chill?

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Could the Sun
play a greater role in recent climate change than has been believed?
Climatologists had dismissed the idea and some solar scientists
have been reticent about it because of its connections with those
who deny climate change. But now the speculation has grown louder
because of what is happening to our Sun. No living scientist has
seen it behave this way. There are no sunspots.

The disappearance
of sunspots happens every few years, but this time it’s gone
on far longer than anyone expected – and there is no sign of
the Sun waking up. “This is the lowest we’ve ever seen.
We thought we’d be out of it by now, but we’re not,”
says Marc Hairston of the University of Texas. And it’s not
just the sunspots that are causing concern. There is also the so-called
solar wind – streams of particles the Sun pours out –
that is at its weakest since records began. In addition, the Sun’s
magnetic axis is tilted to an unusual degree. “This is the
quietest Sun we’ve seen in almost a century,” says NASA
solar scientist David Hathaway. But this is not just a scientific
curiosity. It could affect everyone on Earth and force what for
many is the unthinkable: a reappraisal of the science behind recent
global warming.

Our Sun is
the primary force of the Earth’s climate system, driving atmospheric
and oceanic circulation patterns. It lies behind every aspect of
the Earth’s climate and is, of course, a key component of the
greenhouse effect. But there is another factor to be considered.
When the Sun has gone quiet like this before, it coincided with
the earth cooling slightly and there is speculation that a similar
thing could happen now. If so, it could alter all our predictions
of climate change, and show that our understanding of climate change
might not be anywhere near as good as we thought.

Sunspots are
dark, cooler patches on the Sun’s surface that come and go
in a roughly 11-year cycle, first noticed in 1843. They have gone
away before. They were absent in the 17th century – a period
called the “Maunder Minimum” after the scientist who spotted
it. Crucially, it has been observed that the periods when the Sun’s
activity is high and low are related to warm and cool climatic periods.
The weak Sun in the 17th century coincided with the so-called Little
Ice Age. The Sun took a dip between 1790 and 1830 and the earth
also cooled a little. It was weak during the cold Iron Age, and
active during the warm Bronze Age. Recent research suggests that
in the past 12,000 years there have been 27 grand minima and 19
grand maxima.

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15, 2010

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