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Sunspots, ice ages, and the biggest experiment ever

  • 17 Jun 2011, 11:36
  • Verity

New solar research presented at an American Astronomical Society meeting this week suggests that the next solar cycle might be delayed, or not even happen at all.

This has prompted the sceptic community to rather drastically claim that we're about to enter a new ice age, with James Delingpole proclaiming: "It's official: a new Ice Age is on its way" and Newsnight covering the story in slightly more measured tones.

Whilst there's little doubt that the sun is behaving unexpectedly, to assume that this heralds the dawn of a new ice age is quite a leap to make, and, incidentally, completely disregards current scientific understanding of the issue.

The story has probably arisen from this line of the press release:

"An immediate question is whether this slowdown presages a second Maunder Minimum, a 70-year period with virtually no sunspots during 1645-1715."

 The Maunder Minimum coincided with part of a period of cooling that lasted around 300 years and affected large parts of the globe, known as the 'Little Ice Age'. The prospect of a new Maunder Minimum has therefore prompted some to suggest that an ice age is imminent.

While there is no doubt that solar activity affects climate, it is thought that the effects are relatively small compared to things like the effect of greenhouse gases, although this is hotly contested by climate sceptics.

Assertions of a new ice age have been panned in articles from the New Scientist, Wired and Skeptical Science. Their objection stems from the fact that climate scientists have used models to simulate all manner of solar scenarios, including a repeat of the Maunder Minimum. One study found that a Maunder Minimum-type situation would impose a cooling of around 0.3 ˚C, which although noteworthy is marginal compared to the projected warming of 2 - 4.5 ˚C likely to result from manmade greenhouse gas emissions over the coming century.

So it is reasonable to conclude that solar activity will lead to a slight decrease in global warming, but not the dawn of a new ice age.

Dr Frank Hill of the National Solar Observatory, who presented the new research, supports this, saying:

"We are NOT predicting a mini-ice age. We are predicting the behavior of the solar cycle. In my opinion, it is a huge leap from that to an abrupt global cooling, since the connections between solar activity and climate are still very poorly understood. My understanding is that current calculations suggest only a 0.3 ˚C decrease from a Maunder-like minimum, too small for an ice age. It is unfortunate that the global warming/cooling studies have become so politically polarizing."

 Polarised debate aside, there is an interesting bonus to this situation. One of the main reasons climate models have been developed is because physically experimenting with this sort of scenario is impossible. As Hill points out this actually provides us with an interesting opportunity:

"If our predictions are true, we'll have a wonderful experiment that will determine whether the sun has any effect on global warming."

Will we be entering a new Little Ice Age? Extremely unlikely, according to the science, but the predicted lessening of solar activity over the next few decades could prove to be an interesting natural experiment.

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