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Global cooling? a.k.a. Where have all the sunspots gone?

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Richard Cable | 10:06 UK time, Tuesday, 21 April 2009

The Sun is late. We're meant to be entering a phase of big activity - flares, sunspots and general heliocentric carryings-on - but instead we're getting sullen, ominous non-participation: fifty-year lows in solar wind pressure and radio emissions, and the quietest patch for sunspots in 100-years.

Quite why remains a mystery. As you might expect, a million-kilometre-wide ball of superheated gas measuring 6000°C on the surface isn't the easiest thing in the universe to study, but it's always been accommodating enough to run to a fairly regular 11 year cycle of activity. Until now.

sun_transit_venus226x226.jpgAcademic speculation is rife. Will normal service resume soon? Or are we entering an unexpected cold patch? If this goes on much longer, expect to hear people talking about something called the Maunder Minimum - a period from the late 17th to early 18th century also known as the 'Little Ice Age' - when sunspot activity and temperatures plummeted.

The jury is still out on whether increased sunspot activity makes temperatures on Earth hotter. But should we get excited about the idea that less sunspot activity might make us cooler and offset man-made global warming?

No, says Professor Mike Lockwood of Southampton University, who knows a thing or two about the subject. He was one of the first scientists to identify that the Sun's activity has actually been decreasing since 1985.

'It's pretty clear that the underlying level of the Sun peaked at about 1985 and what we are seeing is a continuation of a downward trend that's been going on for a couple of decades. If the Sun's dimming were to have a cooling effect, we'd have seen it by now.'

Talk of global cooling is considered heresy by many global warming advocates. But then we know that science isn't about orthodoxy, it's about 'observable, empirical and measurable evidence subject to specific principles of reasoning'. It will be interesting to see what happens next.

(P.S. The image on this entry actually shows the Transit of Venus in 2004, rather than a sunspot.)

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