Solar Science

Looking back into the archives, there are many many predictions of the start and size of solar cycle 24 given on the highest possible scientific authority that turned out to be flat out wrong.

Here’s one

March 10, 2006: It’s official: Solar minimum has arrived. Sunspots have all but vanished. Solar flares are nonexistent. The sun is utterly quiet.

Like the quiet before a storm.

This week researchers announced that a storm is coming–the most intense solar maximum in fifty years. The prediction comes from a team led by Mausumi Dikpati of the National Center for Atmospheric Research (NCAR). “The next sunspot cycle will be 30% to 50% stronger than the previous one,” she says. If correct, the years ahead could produce a burst of solar activity second only to the historic Solar Max of 1958.

This is important. The solar minimum began around March 2006 and today August 30, 2009 the Sun is still in that minimum with no sign of it ending.

The failed predictor: The Solar Conveyor Belt Theory

Dikpati’s prediction is unprecedented. In nearly-two centuries since the 11-year sunspot cycle was discovered, scientists have struggled to predict the size of future maxima—and failed. Solar maxima can be intense, as in 1958, or barely detectable, as in 1805, obeying no obvious pattern.

The key to the mystery, Dikpati realized years ago, is a conveyor belt on the sun.

I try to remove some of the waffle here because the article talks about the Earth’s ocean conveyor belt as an analogue but frankly its not relevant, nor useful.

The sun’s conveyor belt is a current, not of water, but of electrically-conducting gas. It flows in a loop from the sun’s equator to the poles and back again. Just as the Great Ocean Conveyor Belt controls weather on Earth, this solar conveyor belt controls weather on the sun. Specifically, it controls the sunspot cycle.

Solar physicist David Hathaway of the National Space Science & Technology Center (NSSTC) explains: “First, remember what sunspots are–tangled knots of magnetism generated by the sun’s inner dynamo. A typical sunspot exists for just a few weeks. Then it decays, leaving behind a ‘corpse’ of weak magnetic fields.”

Enter the conveyor belt.

The Solar Conveyor belt according to NASA

“The top of the conveyor belt skims the surface of the sun, sweeping up the magnetic fields of old, dead sunspots. The ‘corpses’ are dragged down at the poles to a depth of 200,000 km where the sun’s magnetic dynamo can amplify them. Once the corpses (magnetic knots) are reincarnated (amplified), they become buoyant and float back to the surface.” Presto—new sunspots!

Presto! No, it didn’t this time. This time the belt moved to the critical latitude of 22 degrees and we got a single sunspot and that’s it.

All this happens with massive slowness. “It takes about 40 years for the belt to complete one loop,” says Hathaway. The speed varies “anywhere from a 50-year pace (slow) to a 30-year pace (fast).”

When the belt is turning “fast,” it means that lots of magnetic fields are being swept up, and that a future sunspot cycle is going to be intense. This is a basis for forecasting: “The belt was turning fast in 1986-1996,” says Hathaway. “Old magnetic fields swept up then should re-appear as big sunspots in 2010-2011.”

There’s the prediction from 2006. We’ve yet to reach 2010 but Hathaway was talking about 2010-2011 as the time of the SC24 maximum when we haven’t yet reached the end of the minimum in August 2009.

Here’s where the claim of scientific authority is made. This isn’t just any old joe making a prediction, this is expertise:

Like most experts in the field, Hathaway has confidence in the conveyor belt model and agrees with Dikpati that the next solar maximum should be a doozy. But he disagrees with one point. Dikpati’s forecast puts Solar Max at 2012. Hathaway believes it will arrive sooner, in 2010 or 2011.

“History shows that big sunspot cycles ‘ramp up’ faster than small ones,” he says. “I expect to see the first sunspots of the next cycle appear in late 2006 or 2007—and Solar Max to be underway by 2010 or 2011.”

Wrong. An expert strikes out.

Who’s right? Time will tell. Either way, a storm is coming.

It turns out that neither was right. The extended solar minimum caught some of NASA’s brightest experts with their predictive pants down.

I’ve no objection at all and much praise when scientists actually make falsifiable predictions based on their understanding of the science. Thus when David Hathaway predicts that Solar Cycle 24 will be as large or larger than Solar Cycle 23, I applaud that boldness.

In this article on space.com, several aspects to the current solar minimum are discussed:

The sun’s surface has been fairly blank for the last couple of years, and that has some worried that it may be entering another Maunder minimum, the sun’s 50-year abstinence from sunspots, which some scientists have linked to the Little Ice Age of the 17th century.

Could a new sunspot drought plunge us into another decades-long cold spell?

It’s not very likely, says David Hathaway a solar physicist at NASA’s Marshall Space Flight Center in Huntsville, Ala.

Fair enough. Perhaps if I used IPCC-speak, we’d give that a 10-20% probability?

Hathaway continues to make bold observations and predictions:

The sun’s energy drives all climate and weather on Earth. And Hathaway does agree there are good indications that fluctuations in solar output related to sunspot cycles influence the Earth’s climate. And the Maunder minimum isn’t the only evidence — scientists have linked two smaller sunspot minimums (periods of time with very few sunspots) in the early 19th century to cold spells, as well as periods before the Maunder minimum deduced from tree ring records, he said.

But the sun isn’t the only thing that influences our climate: volcanic eruptions, large-scale phenomena such as El Nino, and, more recently, the accumulation of greenhouse gases in the atmosphere also affect the global climate.

Prior to the industrial revolution, the sun probably accounted for about 10 to 30 percent of climate variability, Hathaway told SPACE.com, but now that greenhouse gases have started to build up, “the sun’s contribution is getting smaller and smaller,” he added.

So the pre-industrial climate change on Earth was only 10-30% driven by solar variability. I wonder what the other 70-90% were.

Hathaway hints that volcanic eruptions have an effect, but as far as I am aware such eruptions only cool for perhaps 2 or 3 years, hardly causing a blip in a climate trend [unless we're talking about supervolcanic events which can cause climate cooling for decades, but we haven't had one of those for 70,000 years with the Toba explosion]. Is the rest caused by the ENSO cycle?

What of the current solar minimum and the sputtering start to Solar Cycle 24?

Signs of the current, new solar cycle (which actually overlaps with the last cycle) showed up in November 2006, and its first sunspots were seen in January of this year, and again in April, Hathaway said. So already that rules out another Maunder minimum, Hathaway says, since this solar cycle has already begun producing spots, even if there haven’t been many of them yet.

This cycle is just simply “off to a slow start,” Hathaway said.

The last three solar cycles were also what Hathaway calls “big cycles,” meaning they had more than the average number of sunspots (the average is around 110 to 120 sunspots on any given day during the cycle’s maximum). It’s not unusual for such a spate of prolific cycles to be followed my more muted solar cycles (such as the cycle that preceded the last three biggies).

Hathaway says that solar physicists are divided on their predictions of this new solar cycle — some say it will be small, others say it will be another doozy. Predictions have ranged anywhere from 75 to 150 maximum spots during its peak. “There really are two camps,” Hathaway said. Whatever the number ends up being, though, “it’s not zero,” he added.

That depends on whether the Maunder Minimum was really devoid of sunspots or had sporadic “Tiny Tim” spot groups which were not seen because of the technology used at the time.

It’s doubtful that it was really zero during that time.

Here’s the clincher:

Why the sun is so fickle in its sunspot production is still something of a quandary. “We still don’t fully understand how the sun does this,” Hathaway noted.

Now that statement I regard as the most important of the article. It might not be a popular statement with people on either side of the argument, but as far as solar cycle prediction is concerned, nobody knows for sure what will happen with the Solar Cycle next week, never mind next year or five or ten years hence.

The science of the variation of the Sun’s solar cycle is in its vary early stages. No-one, not even David Hathaway, knows what will happen next. That’s why he’s checking the Sun every day.

As Kenneth Tapping has already reported (and I blogged his observation) long solar cycles are not that unusual historically and are not in themselves indicative of how powerful are the succeeding cycles. Tapping noted that the long and weak Solar Cycle 20, (which occurred during a global cool period on Earth), was succeeded by Solar Cycles 21, 22 and 23 all of which were relatively powerful (and coincided by chance with a global warming on Earth).

But on the point of whether even a Maunder Minimum style collapse would cool the Earth, Hathaway admirably sticks with the IPCC-derived consensus:

One idea springs from the fact that the sun emits much more ultraviolet radiation when it is covered in sunspots, which can affect the chemistry of Earth’s atmosphere. The other is that when the sun is active, it produces tangled magnetic fields that keep out galactic cosmic rays. Some scientists have proposed that a lack of sunspots means these cosmic rays are bombarding Earth and creating clouds, which can help cool the planet’s surface.

But these ideas aren’t yet proven, and anyway, the sun’s contribution is small compared to volcanoes, El Nino and greenhouse gases, Hathaway notes.

Even if there were another Maunder minimum, he says, we would still suffer the effects of greenhouse gases and the Earth’s climate would remain warm. “It doesn’t overpower them at all,” Hathaway said.

So according to Hathaway, greenhouse gases are warming the Earth to such an extent that solar variation becomes unimportant. Never mind whether I agree with him (and who am I to disagree with an expert?), I applaud David Hathaway for making such scientifically falsifiable statements.

I hope he’s right about the warming. So far, during the current warming, we’ve had the major deserts contract, the tropics expand and possibly a general reduction in hurricane frequency globally during the 20th Century.

From NASA website:

Solar cycle 24, due to peak in 2010 or 2011 “looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago,” says solar physicist David Hathaway of the Marshall Space Flight Center. He and colleague Robert Wilson presented this conclusion last week at the American Geophysical Union meeting in San Francisco.

Their forecast is based on historical records of geomagnetic storms.

Hathaway explains: “When a gust of solar wind hits Earth’s magnetic field, the impact causes the magnetic field to shake. If it shakes hard enough, we call it a geomagnetic storm.” In the extreme, these storms cause power outages and make compass needles swing in the wrong direction. Auroras are a beautiful side-effect.

Hathaway and Wilson looked at records of geomagnetic activity stretching back almost 150 years and noticed something useful:. “The amount of geomagnetic activity now tells us what the solar cycle is going to be like 6 to 8 years in the future,” says Hathaway. A picture is worth a thousand words:

Hathaway's comparison of solar and geomagnetic fields

Above: Peaks in geomagnetic activity (red) foretell solar maxima (black) more than six years in advance. [More]

In the plot, above, black curves are solar cycles; the amplitude is the sunspot number. Red curves are geomagnetic indices, specifically the Inter-hour Variability Index or IHV. “These indices are derived from magnetometer data recorded at two points on opposite sides of Earth: one in England and another in Australia. IHV data have been taken every day since 1868,” says Hathaway.

Cross correlating sunspot number vs. IHV, they found that the IHV predicts the amplitude of the solar cycle 6-plus years in advance with a 94% correlation coefficient.

“We don’t know why this works,” says Hathaway. The underlying physics is a mystery. “But it does work.”

And here’s the prediction for Solar Cycle 24 based on this “mystery”:

Hathaway's 2006 prediction of SC24

Never mind that this thing looks a lot like numerology – if its from NASA and has a nice graph it must be worth something