Is a mini-ice age coming in 2030, and does the sun have two dynamos?

Is the Sun driven by two dynamos, each running on slightly different 11 year cycles?

Many people are talking about a new forecast of a mini-ice age (which seems to be an increasingly popular thing to predict.) This one comes from a paper published last year but presented at the Royal Astronomical Society last week. Shepard, Zharkov and Zharkova may have gotten us a step closer to understanding why the solar cycle varies in length from 8 to 14 years. Since the level of solar activity correlates with both the the length of the current solar cycle and the surface temperatures on Earth one solar cycle later (the notch-delay theory, and see the work of David Archibald), it may make it possible to predict the climate decades in advance. (With the caveat that this new study is still a model, correlation is not causation, etc.)

One of the better descriptions comes from Astronomy Now.

The Sun, like all stars, is a large nuclear fusion reactor that generates powerful magnetic fields, similar to a dynamo. The model developed by Zharkova’s team suggests there are two dynamos at work in the Sun; one close to the surface and one deep within the convection zone. They found this dual dynamo system could explain aspects of the solar cycle with much greater accuracy than before — possibly leading to enhanced predictions of future solar behaviour. “We found magnetic wave components appearing in pairs; originating in two different layers in the Sun’s interior. They both have a frequency of approximately 11 years, although this frequency is slightly different [for both] and they are offset in time,” says Zharkova. The two magnetic waves either reinforce one another to produce high activity or cancel out to create lull periods.

With the Sun, we struggle for good data. Shepard et al only have three sunspot cycles of magnetic field data to go on but used the longer sunspot records as well.

The debate on this one is certainly not over. The new paper suggest there are two solar dynamos but in 2011 Nicola Scafetta argued that solar dynamics is best modeled with three interference circulation modes. His model reproduces past solar activity for millennia and also predicted a grand minimum by 2030.

Guest post by Dr David Evans

Dr David Evans, 14 July 2015, David Evans’ Notch-Delay Solar Theory and Model Home

The topic is a prediction publicized over the weekend that “Solar activity predicted to fall 60% in 2030s, to ‘mini ice age’ levels“. This is quite plausible, because it fits with several other predictions made in 2013 by a number of authors (Special Issue of Pattern Recognition in Physics, Mörner, Tattersall & Solheim, 2013).

Be aware that “solar activity” refers to the number of sunspots, not the total energy output of the Sun — which is very near constant and has varied less than 0.15% over the last 400 years. It’s not as if the Sun is going to be producing 60% less heat: it will produce almost exactly the same heat as it always does, just with far fewer sunspots.

However, even this is very significant. Last year we blogged that the number of sunspots accurately predicts the small changes in temperature here on Earth, such as those associated with global warming, but with a delay of one sunspot cycle (which averages 11 years, but is only half the Sun’s full cycle, which averages about 22 years).

There was a largish fall in solar activity in 2004 (in 11 year smoothed TSI), so there will be a significant and sustained fall in global temperature on Earth starting in about 2017 (the current sunspot cycle is a long one, about 13 years, 2004 + 13 = 2017). This will outweigh the warming effect of extra carbon dioxide.

The Earth has been in a warming trend for the past 350 years, since the depth of the Little Ice Age during the Maunder Minimum, in the second half of the 1600’s. This warming trend appears to be driven by solar activity—carbon dioxide didn’t start increasing until 1800 or so, and didn’t really get going until after WWII with post-war industrialization.

So the Shepard paper’s prediction that the Sun is going inactive, and will lead to a cooler Earth such as last seen in the Maunder Minimum of the 1600s (when ice fairs on the Thames River in London were common), is plausible and likely.

Note that the influence of sunspots on terrestrial temperatures is not because the heat of the Sun varies (that variation is pretty insignificant in terms of global warming or cooling). It is because something about the Sun, perhaps its UV output or a magnetic influence on the Earth’s upper atmosphere, affects the cloud cover on Earth, and thus how much sunlight the Earth reflects back out to space. More clouds mean more sunlight is reflected without warming the Earth, so the Earth is cooler. If the Sun is affecting the cloud cover on Earth, it is affecting the Earth’s temperature even though the heat from the Sun stays about constant.

Note also that the delay of one sunspot cycle (averaging 11 years) mentioned above, between the change in solar activity and Earthly temperatures, is because there is a half-cycle delay between sunspots and “force X”. Force X is the name we’ve given to the solar influence on Earth’s cloudiness–the “X” is because we aren’t sure what it is, like “x-rays” were so named because by their discoverer William Röntgen because he didn’t know what they really were. The Sun’s full cycle is around 22 years – the sunspot “cycle” is only half of it, because the number of sunspots goes as the square of the magnetic field strength so the positive and negative phases of the 22-year cycle look the same in terms of sunspots. The sunspots merely signal where force X will be in about 11 year’s time.

This is a bit like a four stroke combustion engine, which has four phases (suck, squeeze, bang, blow). If you know how much fuel and air is sucked in during the “suck” phase then you know how much power will be produced in the “bang” phase, which comes half a cycle (or two phases) later. Similarly with the Sun: the sunspots (or solar activity) tell us how much force X there will be half a full cycle (about 11 years) later.

The finding in the Shepard paper that the Sun has two dynamos is exciting for force X, making it quite plausible that the UV or magnetic effects that constitute force X are following the trends in bulk radiation produced by the dynamos.

The IPCC does not include any solar influence in the climate models except the direct heating by the Sun. But the total radiation from the Sun is almost constant — it is even known as the Solar Constant, because it wasn’t found to vary until observed by satellites starting in 1979. So, along with Bloomberg, NASA, and the IPCC, we say that changes in solar activity will have only a negligible direct effect.

There are some major updates concerning the notch-delay theory, which we will be blogging on soon.

What would be the impact on the climate?

If Shepard and Scafetta are correct about the upcoming dearth of solar activity by the 2030s, by 2040 it will have cooled significantly, by maybe 0.5C to 1.0C, undoing the global warming since 1800 or even 1700. That cooling could start as early as 2017. This cooling would be counteracted by a mild warming due to rising carbon dioxide, but the net effect would be cooling.

The ratio of La Ninas to El Ninos will presumably increase, making for slightly more floods and fewer droughts in eastern Australia.

A Maunder type phase of the sun,

Could put climate-change hype on the run,

When predictions would crumble,

And temperatures tumble,

As a Mini Ice Age had begun.

–Ruairi

REFERENCES

Simon J. Shepherd, Sergei I. Zharkov, and Valentina V. Zharkova (2014) Prediction of Solar Activity from Solar Background Magnetic Field Variations in Cycles 21-23, The Astrophysical Journal, 795 46 doi:10.1088/0004-637X/795/1/46

Scafetta, N.: Multi-scale harmonic model for solar and climate cyclical variation throughout the Holocene based on Jupiter–Saturn tidal frequencies plus the 11-year solar dynamo cycle. Journal of Atmospheric and Solar-Terrestrial Physics 80, 296–311 (2012).

h/t Terry D, Colin, Stephan, Tom, Turtle, Joffa and Eric Worrall. Also in comments, Pat, el gordo, aussieute, CCreader, others, thanks!

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