Sunspots, ice ages, and the biggest experiment ever
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
"It's official: a new Ice Age is on its way" and
Newsnight covering the story in slightly more measured
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
"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
Assertions of a new ice age have been panned in articles from
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
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
"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