By Erica Mather 15/07/2015 6


“Earth heading for ‘Little Ice Age’ in 15 years”, “The Little Ice Age cometh”, and the obligatory “Winter is coming”.

They are just some of the headlines that have run around the world following a new analysis of sunspot cycles presented by Northumbria University’s Professor Valentina Zharkova at a conference organised by the Royal Astronomical Society.

But as the Washington Post points out, the trending story wasn’t all that it seemed, with no mention by the scientists of a return to Little Ice Age conditions.

“Instead, we got 300-year-old engravings of Londoners cavorting on the frozen River Thames accompanied by predictions of food shortages and brutal cold — plus snarky tweets about not worrying about global warming anymore,” wrote the Washington Post’s Sarah Kaplan.

The context

According to a new model by UK researchers, the activity of the Sun is predicted to fall by 60 per cent during the 2030s.  The same reduction in activity has not been observed since 1645 when the last ‘mini ice age’ began.

The group led by Zharkova, presented their model that accurately predicts irregularities in the Sun’s solar cycle at the recent National Astronomy Meeting in Llandudno.  The Sun’s solar cycle lasts between 10 to 12 years, and its’ activity during this time has been found to fluctuate.  Previous models have struggled to account for these fluctuations as well as the slight variance in each cycle.

The unpublished study extends the conclusions of other solar physicists’ who believe the solar cycle is caused by a dynamo generated by convecting fluid deep within the Sun.  Zharkova’s team theorise that with the addition of a second dynamo, situated close to the surface, the irregular solar cycle can be extremely accurately explained.

The predictions were compared to and closely matched the average sunspot numbers, a strong indicator of solar activity.

A comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle.  Many more sunspots, solar flares, and coronal mass ejections occur during the solar maximum. The increase in activity can be seen in the number of white areas, i.e. indicators of strong magnetic intensity.
A comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun’s 11-years solar cycle. Many more sunspots, solar flares, and coronal mass ejections occur during the solar maximum. The increase in activity can be seen in the number of white areas, i.e. indicators of strong magnetic intensity.  Photo credit: SOHO/ESA/NASA

The model predicts future solar cycles by examining the timing of the magnetic waves originating at the two different layers of the Sun.  During approaching cycles, the waves are predicted to become increasingly out of synch, particularly between 2030-2040.  “Effectively, when the waves are approximately in phase, they can show strong interaction, or resonance, and we have strong solar activity. When they are out of phase, we have solar minimums. When there is full phase separation, we have the conditions last seen during the Maunder minimum, 370 years ago,” said Zharkova.

Truth is in the nuance

While the media latched onto the projected decrease in activity of the sun as triggering a mini Ice Age here on Earth, the evidence presented by the scientists doesn’t support that conclusion.

The Science Media Centre collected expert commentary to elucidate whether the predicted decrease in solar activity will result in a significant decrease in global temperatures.

Prof James Renwick from Victoria University of Wellington emphasises the correct interpretation of the predicted reduction in the Sun’s activity.  Rather than a 60 per cent decrease in solar output, there is “…a 60% reduction in the peak of the solar (sunspot) cycle, so we are talking about less than 0.1% decrease in total solar output.”

Associate Prof Sean Oughton from the University of Waikato confirms that the predicted reduction in solar activity corroborates with other models, but debates whether it will exactly resemble that of the last ice age.  Oughton cautions the extrapolation of the findings.  “…the conditions ON THE SUN will probably be similar to those during the Maunder minimum.  Of course that does not require that the conditions on the earth will be similar to those during the Maunder minimum.”

The large increase in the amount of greenhouse gas in the atmosphere since the 1700s must be taken into consideration.  Prof Renwick states that this increase has “added more than 2 Watts per square metre in the energy absorbed at the ground, compared to the 1700s.”  Therefore if the new model is correct, Prof Renwick predicts global warming effects would be negated for 20-30 years.

“Overall, the globe would go back for a while to conditions experienced in the first half of the 20th century. Once the solar cycle strengthened again, we would be back to greenhouse gas-related warming again.”

In order to confirm the validity of this model, both experts emphasise the need for peer-review and further testing using other data sets.


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