My interest was piqued a few days ago by this story in the Independent by an astronomer called David Whitehouse, which was reproduced in one of the Sunday papers down here in South Africa. The article claimed that the roughly 11 year cycle of sunspot activity appears to have stalled – the present minimum, the end of solar cycle 23, has gone on for much longer than expected, and there are no signs of it ending. It then said that we are possibly witnessing the first signs of a repeat of the Maunder minimum, a 70 year period in the 17th and early 18th centuries when sunspots virtually disappeared, which also roughly coincides with the Little Ice Age. Here’s the concluding paragraph:
Perhaps the lateness of cycle 24 might even be the start of another Little Ice Age. If so, then our Sun might come to our rescue over climate change, mitigating mankind’s influence and allowing us more time to act. It might even be the case that the Earth’s response to low solar activity will overturn many of our assumptions about man’s influence on climate change.
Leaving aside the fact that that last sentence rings a few denialist alarm bells, I wondered exactly what is going on with the sunspot cycle – has it really gone that quiet? Fortunately, Tamino over at Open Mind posted on this very subject a couple of months ago, and it turns out that claiming a total shutdown is – to put it mildly – somewhat jumping the gun:
Solar cycles don’t follow simple patterns; although the solar cycle is dominated by a roughly 11-year period, the timing and strength of each individual cycle is different…
…The next cycle is later than expected; current estimates are that it may start as late as March of 2008. But this is not later than average, a March ’08 beginning will mean that cycle 23 lasted 11 years, just about average*. The collected predictions of the strength of the upcoming cycle span a range from very strong to very weak.
*[according to this comment, this is slightly mistaken – cycle 23 has lasted 11.83 years, which is higher than average but not yet the longest on record]
Besides, even if the sun was about to enter a prolonged minimum, using it as an excuse to delay doing anything about anthropogenic forcing of the climate would be pretty daft – if the sun can unpredictably shift into a low activity state and cancel out some of the projected warming from increased CO2, it can unpredictably shift out of it just as easily.
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