The Weakest Solar Cycle in 100 Years


Sunspot cycle
D. Hathaway / NASA / MSFC
The Sun is acting weird. It typically puts on a pageant of magnetic activity every 11 years for aurora watchers and sungazers alike, but this time it overslept. When it finally woke up (a year late), it gave the weakest performance in 100 years.

What’s even weirder is that scientists, who aren’t usually shy about tossing hypotheses about, are at a loss for a good explanation. Three scientists, David Hathaway (NASA / Marshall Space Flight Center), Giuliana de Toma (High Altitude Observatory), and Matthew Penn (National Solar Observatory) presented possible explanations at this month’s meeting of the American Astronomical Society’s Solar Physics Division, but their results sparked a lively debate rather than a scientific consensus.

A Weak and Weird Solar Cycle

Sun's magnetic field: A Solar Cycle
The Sun rotates faster at its equator, which stretches the magnetic field lines around the solar surface.
© Addison Wesley
A well-behaved Sun flips its north and south magnetic poles every 11 years. A cycle starts when the field is weak and dipolar—basically, a giant bar magnet. But the Sun’s rotation is faster at its equator than at its poles, and this difference soon stretches the field lines like distended rubber bands around the solar surface. Frenetic activity ensues, with magnetic tangles producing sunspots, prominences, and sometimes flares and plasma explosions. All of that dies down when the Sun-wide magnetic field lines finally snap into simpler configurations, re-establishing the dipole field and beginning the next cycle.

The Sun has been doing all of that, just to a lesser degree. “Not only is this the smallest cycle we’ve seen in the space age, it’s the smallest cycle in 100 years,” says Hathaway, who took part in the Solar Cycle 24 Prediction Panel back in 2007.

Sun's asymmetric poles
The current cycle isn't just weak. Starting in 2006, the Sun's poles became asymmetric, with the south pole lagging behind the north for the past 7 years. Asymmetric poles are common enough, but they usually synchronize within a year or so.
G. de Toma / USAF / NOAO
The panel members were split at the time on whether the next solar activity cycle would be strong or weak, but their middle-of-the-road estimate anticipated 90 sunspots as a peak value near August 2012. Instead, the peak sunspot number seems to be less than 70, and the maximum arrived later than expected. Cycle 24 should have peaked in 2012, 11 years after its last minimum in 2001, but the Sun overslept by a full year, waking up in 2013 instead.

And its waking has been asymmetric: the north pole has led the cycle since 2006, with the south pole lagging behind. “It’s not uncommon to see hemispheres going out of phase . . . Usually this [asymmetry] lasts a year or so and then the hemispheres synchronize,” de Toma explains. “We don’t know why this is lasting for so long.”

Explaining Weirdness

Sun cycle history
Cycle 24 is the weakest cycle in 100 years. This might be part of a centennial tapering of magnetic activity known as the Gleissberg cycle.
D. Hathaway / NASA / MSFC
It’s possible that, weak and weird as it is, Cycle 24 is still part of the Sun’s normal variation, even if it’s one of the weakest cycles yet recorded.

In fact, both Hathaway and de Toma think the 11-year cycle might be part of a larger one. Historical records show weak cycles at the turn of the 19th and 20th centuries, so it could be that the solar cycle tapers every 100 years or so in what’s known as the Gleissberg Cycle. It’s not easy to establish the existence of a cycle that turns over on such a long timescale, and even Hathaway admitted, “Certainly I don’t understand how it works.”

Doug Biesecker (NOAA), chair of the most recent prediction panel, says, “I remain highly skeptical . . . [Even] if you believe there is a 100-year cycle, then that still doesn't tell us why. Just that it is.”

Penn offered another, more catastrophic option: the sunspot cycle might die altogether. His team uses sunspot spectra to measure their magnetic fields, and his data show a clear trend: the magnetic field strength in sunspots is waning.

Sunspots' magnetic field
Penn's research shows that sunspots' magnetic field strength is declining over time. Sunspots can only form if the magnetic field is greater than around 1,500 Gauss, so if the trend continues, we could be headed for a time where no spots appear on the Sun's surface.
M. Penn
“If this trend continues, there will be almost no spots in Cycle 25, and we might be going into another Maunder Minimum,” Penn states. The first Maunder Minimum occurred during the second half of the 17th century. Almost no spots were seen on the Sun during this time, which coincided with Europe’s Little Ice Age.

But Penn acknowledges that magnetic field measurements from other studies don’t always see the same trend he sees. Some observations show that sunspots’ magnetic field strength varies with the solar cycle, and others (including de Toma’s) show that sunspots’ magnetic fields aren’t changing with time. De Toma was even able to reproduce Penn’s results by excluding small sunspots, suggesting Penn’s trend might result from the way his team selects the sunspots they measure.

Another word of caution came from Hathaway, who notes that the Maunder Minimum might have been a catastrophic event rather than a gradual trend. “Many of my colleagues are poring over historical records to find out . . . what did lead up to the Maunder Minimum?” he says. “New observations suggestion that the cycle before the Maunder Minimum wasn’t particularly small.”

Regardless of what’s causing the Sun’s strange behavior, Hathaway and Penn, who are both in the solar prediction business, anticipate that Cycle 25, expected to peak in 2024, will be the weakest yet.

Penn’s prediction is based on the weakening magnetic field he sees within sunspots; Hathaway’s are instead based on measurements of the Sun’s polar field and the meridional flow, the flow of magnetic flux from the Sun’s equator to the poles. A stronger flow would help strengthen weak fields, but meridional flows have been completely absent in Cycle 24 so far. We might have a long wait ahead of us to see if and when the Sun recovers.

26 thoughts on “The Weakest Solar Cycle in 100 Years

  1. CosmicLettuce

    Worrying about changes over 100 years of the lifetime of the sun is equivalent to worrying about 1 minute in the course of a human lifetime. Is how you behave in one minute of your life a "sign of a deeper trend"??? Perspective, people!!!!

  2. Frank ReedFrank Reed

    Person using the handle "CosmicLettuce", you seem to have mis-read the article. There is no suggestion here that the Sun is "dying" or that there is anything fundamentally changing in the Sun’s basic energy output. The "deeper trend" referred to is clearly a longer trend in the sunspot cycles. The sunspot cycles and the resulting "space weather" have a significant impact on radio communications, GPS positioning, satellite orbital decay, power grids, and other technological matters, as well as likely, though unproven, impacts on climate and weather. If this present weak cycle is in fact a sign of a deeper trend, then it is absolutely newsworthy and relevant and you should adjust your perspective if you don’t see that. A Sun with a quiescent sunspot cycle could save civilization globally hundreds of billions of dollars in various ways over a fifty year period. But it could also generate dangerous complacency which could bite us hard when the cycles become strong again. And no one has any idea how to predict this.

  3. Bruce Mayfield

    But on the other hand (from CL’s comment), since the sun’s output is far and away the most important factor in how hot it is here on earth, determining the rate of change (if there is any) in the sun’s output even during human scale time frames could be very important. Frank Reed, I agree almost completely with your comment, accept, hasn’t the case been “proven” that the human caused CO2 atmospheric increase is starting to cause climate and weather change? I know that there are many doubters, but hasn’t the science community come to a consensus on this? Also, 2 more questions. Is there any measurable change in the energy earth receives between the highs and lows of the 11 year sunspot cycle? And if there isn’t, what accounts for the time correlation between the Maunder Minimum and the Little Ice Age?

  4. dusanmal

    "Is there any measurable change in the energy earth receives between the highs and lows of the 11 year sunspot cycle? And if there isn’t, what accounts for the time correlation between the Maunder Minimum and the Little Ice Age?" – question is not so much about the total energy received but about its distribution over low and high energy particles. CERN research famously hushed up by the directors in 2011 ("you can publish the numbers but not interpret them") confirmed long existing theory (that originally emerged from known long term correlation of Earth’s global temperature and Be isotope concentrations in related strata) that can be simplified to "if energy Earth receives comes in form of particles with higher individual energies – the process of warming is more efficient due to the interaction of those particles and water vapor in the atmosphere". So, Solar cycle related warming and cooling is not so much about total energy received but more high energy particles – as in Solar maximums.

  5. dusanmal

    @BruceMayfield "hasn’t the case been “proven” that the human caused CO2 atmospheric increase is starting to cause climate and weather change?" – unfortunately individual and Governmental ideology have had impact on "proven" issue. In my opinion there are two experimental facts that highly challenge (and disprove) that theory:
    1) Find MIT/NASA satellite global temperature study from late 1990’s. Evidence: global temperatures rose each year; CO2 concentrations went up each year; … proportion of the energy Earth returned to space to incoming energy ROSE EACH YEAR (measurable, way beyond error limits).
    Definition of greenhouse effect: system receives some energy, absorbs some, returns some, amount o absorbed energy keeps system at temperature T1. We introduce some greenhouse factor that reflects back some of returned energy. More energy is absorbed, system is at higher T2>T1. LESS energy is reflected to the surroundings. MIT/NASA precise, long term study EXCLUDES any form of greenhouse effect as a cause of Earth warming during that period. Natural CO2, human produced CO2, something else we know of or do not know of,… Simply whatever warmed the Earth couldn’t have been a greenhouse effect of any kind. (See my first reply – greater efficiency of utilizing received energy could do this).

  6. Bruce

    Dusanmal, thank you for those answers. Your first comment explained how even with steady overall energy coming from the Sun we could still have differing heating of the Earth’s atmosphere depending upon the levels of magnetic activity on the Sun. I find it a bit ironic that to some the obvious fact that the Sun is the main driver in global temps is also “an inconvenient truth.” In a perfect world scientists would be free to collect data and draw objective, unbiased conclusions based purely on fact and logic. But with vast sums of money involved on both sides of the global warming issue the public is left wondering, whose experts can we trust? Meanwhile global weather certainly seems to be getting more and more extreme, and almost all glaciers the world over are in serious retreat. (If any are in doubt on this second point, watching the film “Chasing Ice” should be eye opening.) Dusanmal’s second posting casts doubt upon manmade CO2 as being responsible for global warming, but is his reasoning sound?

  7. Dieter Kreuer

    The solar activity has very little to do with its energy output and thus the amount of energy reaching Earth. The energy leaving the Sun as light and heat has its origin deep within its core, where fusion is happening at a very constant rate. The solar activity that we see in sunspots, faculae and prominences is generated much higher up by magnetic effects within the electrically guiding plasma. Which is very different again from the effect that drives pulsating variable stars.
    Whether the Maunder minimum of sunspots was the actual reason for the cold winters in Europe at all is by no means established, and then, it was a regional effect. Please see this excellent article by the "Bad Astronomer" Phil Plait:

  8. Frank ReedFrank Reed

    Bruce, just so we’re clear, I didn’t say anything AT ALL about CO2 and climate. I said that there were "unproven impacts on climate and weather" related to the sunspot cycle –an entirely different question (and the topic of this article). In Phil Plait’s blog article, mentioned in the previous comment, he paraphrase Doug Biesecker saying he "points out that a weak cycle may not have an effect on our climate; we simply don’t know for sure." BUT it has long been considered a reasonable scenario nonetheless. Though the Sun’s overall energy output is very likely constant to a high degree of accuracy, and actual measurements from orbit show little measurable variation, slight variations in the spectral distribution of sunlight and also its latitudinal distribution (sunspots do not occur near the Sun’s poles) could easily have some effect on the Earth’s climate, especially if the sunspot cycle actually shuts down, which at this point is only a small possibility –we just don’t have a lot of data on this. These discussions have their own "cycles". It has become less fashionable in recent years to discuss external forcing of Earth’s climate since many people fear that it will distract attention from internal forcing and anthropogenic warming. That’s a shame…

  9. Peter WilsonPeter

    At some point we could quit arguing about it, and just accept that whatever natural forces governed climate in the past, God has now put mankind in charge of maintaining conditions conducive to life in the future. Look at the famous “hockey stick” graph. Before the recent upwards spike, global temperature was trending down. The Earth’s orbit is changing back into ice-age conditions. The Little Ice Age was a taste of what was to come. We have burned enough buried carbon to stave off the next ice-age. Phew! We should not be arguing about whether or not we can impact climate; the debate should be over what temp to set the thermostat at.

  10. Bruce

    Frank Reed, yes, I did realize that your first posting was about the solar magnetic threat and not global warming, but one could make somewhat similar arguments about the global warming issue too. And, let me clarify as well, I’m not in the manmade global warming deniers club, even though I made a comment entitled “Sun Driven Global Warming”. But one hears this argument so often, and since this fact is so significant (we do get almost all our warmth from the sun, after all) any story about changes in the Sun are bound to be seized upon by those who want to let man off the hook and blame it all on old Sol. But I’m just a guy trying to sift out the facts from the hype and spin so that I can come to a well reasoned fact based opinion. So I thank Dieter Kreuer for providing the link to Phil Plait’s writings which were very helpful, showing that the Maunder Minimum/Little Ice Age connection doesn’t prove as much as it may at first seem. But we still have Dusanmal’s “What is Greenhouse effect?” post, which no one has contested yet …

  11. Bruce

    Dusanmal, thanks again for your answers. In my second post of this thread I responded to your first post, but I think your second comment isn’t nearly as sound as your first. The fact that CO2 is a greenhouse gas is provable in a lab, isn’t it? You admit that global temps and CO2 percentages are both on the rise, but then you seem to be making a point that the ratio of outgoing to incoming energy increasing is a problem. Since incoming energy (from the Sun) is reasonably constant, if the Earth’s temp rises then the amount of heat radiated back into space will also rise, increasing this ratio. In fact the ratio of outgoing to incoming energy is and always has been over 1, because in addition to solar heating the earth is also continually shedding heat that has flowed up from its interior. And now we have humanity burning fossil fuels at an ever increasing pace, adding to the heat each year. Slash and burn and overly frequent plowing agricultural practices also add to the heating. Cities are known to be “heat islands” with warmer local temps, and the size of cities grow with increasing human population, which raises the overall average. Hey, wait a minute; did I just explain anthropomorphic global warming without invoking the greenhouse effect??? See how many factors are at work here! Yes Peter, the debate about whether we are impacting climate should be over. But what should be done about it is the 64 trillion dollar question.

  12. Eric Holcomb

    The post claiming "whatever warmed the Earth couldn’t have been a greenhouse effect of any kind" is simply wrong. There are other variables such as ocean surface temperatures (influenced by El Nino and La Nina) that affect the amount of thermal radiation returned to space. When these are accounted for, researchers find no significant discrepancies in climate models that predict warming with increasing greenhouse gas concentrations. Indeed, the oceans are still increasing in heat content at a significant rate, with recent evidence indicating that some of the heat is going into the deep oceans. All of this despite relatively mild solar activity in recent years.

  13. Anthony Barreiro

    Thanks Dr. Young for this clear and interesting report. To everyone else — Aside from the practical effects of solar radiation on vulnerable technologies and the possible correlations between solar activity and terrestrial climate, the anomalies between this solar cycle and previous cycles, and the befuddlement of the scientists who study the Sun, are just plain interesting! The Sun is the only star we can image and study in such close detail, so it’s our best sample of the population of all the other stars, although almost certainly a skewed sample. E.g., the Kepler space telescope discovered that on average "Sun-like stars" are slightly more variable than dear old Sol. The things we don’t understand about our own Sun are, ipso facto, an important area of study for astronomy generally.

  14. Jim-BaughmanJim Baughman

    I am fully prepared to receive a storm of criticism for this post, but nonetheless it needs to be stated. There is currently NO data to indicate that the multi-event Ice Age cycle of the past couple million years has come to an end. What if we are merely in yet another interglacial warm period, and that sooner or later the ice sheets will come back. In fact historical data, derived from core samples, suggests that the onset of an ice age is quick, a matter of decades, and often they are foreshadowed by unexplained warming cycles just prior to onset. Man is definitely warming the planet, no doubt about that at all, but glacier records from the Swiss Alps show that they were receding steadily throughout the 1700’s, well prior to the advent of the Industrial Revolution. So we seem to be experiencing warming from two sources; man and his heedless burning of fossil fuels, but also a larger cycle that just might prefigure a plunge into yet another ice age. I predict this will happen in the lifetimes of some who are alive today. By 2050 deep snowfalls will be a regular occurrence in cities like Los Angeles and Phoenix, both of which have no historical record of such a thing.

  15. Trane Francks

    @Bruce Mayfield: "hasn’t the case been “proven” that the human caused CO2 atmospheric increase is starting to cause climate and weather change?"

    Anybody with experience analyzing closed systems knows very well that you cannot fiddle with the parameter values of the system without having consequences. One does not simply remove 40% of the planet’s CO2-sequestering canopy and replace it with pasture, CAFOs, manmade structures and fill the free space with cars, trucks and airplanes …. and then expect no changes.

    There is ALWAYS cause and effect. The question, therefore, is not whether we’re having an effect, but whether the amount of input to the system is sustainable. Given the complexities of particulate causing global dimming, it’s just not straight forward to recognize at what point we’re at the point of no return. That said, after 9/11 when all the air traffic was grounded, particulate in the atmosphere decreased and we saw immediate ground-level temperature increases of 1-2 deg C within days.


    The problem is that "energy returned to space" can be the amount reflected from particulate and aerosols before it reaches the surface. What we’re mostly concerned about is the amount of energy that is reaching the ground and how much of that overall energy that is staying in the system is being released. Unfortunately, the maths don’t look good there.

    Even if we take your statements at face value, however, it makes zero sense to stick with 30-year-old data as Truth. So, how about we fast forward to 2009 and see what MIT has to say this time?

    Oops. Not nearly so good anymore.

  16. Bert Molloy

    2004 article:
    About the long-term coordinated variations
    of the activity, radius, total irradiance of the
    Sun and the Earth’s climate
    Habibullo I. Abdussamatov
    Pulkovo Observatory, Saint Petersburg, Russia

    Prediction, (dating from 1998): Weaker Solar Cycle 24, almost non-existant solar cycle 25, 26 and likely 27.

    So far he is a lot closer than the IPCC’s experts.

    Bert Molloy

  17. Stephen W. Ramsden

    I don’t understand what the reason for hyping this is or why any major periodical supporting astronomy would put out so many negative stories dissuading people from possibly getting involved in solar astronomy.

    Perhaps the data indicates that this is a weak solar cycle, I believe it is simply interpreted this way for the purpose of this article, but either way…WHO CARES!!? How about SUPPORTING the hobby instead of always talking about how low the activity is? These articles are always spread by people who have never looked through an H-Alpha scope or by nighttime astronomers who think they have “”uncovered” something important about a hobby they know almost nothing about.

    I can tell you for absolute certainty that if you get out a solar scope and look through it-the first thing that comes to your mind will be how incredibly fascinating it is to look at the Sun, you’re probably not going to say “Wow, what a weak solar cycle” .

    Can we get more positive news about our hobby instead of this constant ignorance or downright naysaying about the absolute fastest growing portion of modern astronomy-Solar?

  18. Bruce

    Jim Baughman, wow dude, what a CHILLING prediction. (Sorry, but it needed to be stated.) But as somewhat of a contrarian myself, your radical suggestion does have a certain degree of fringe appeal. But if people were to heed your warning then people should heedlessly continue the “heedless burning of fossil fuels”??? Sorry Jim, but I think Peter is more likely correct when he quipped that ‘we have staved off the next ice-age’. But if I had to make a prediction (which I don’t, so I’m not) I’d have to say that it is far more likely that we might see the opposite disaster, a total melt-down and shift completely away from glacial coverage resulting in massive sea-level rise. (I wonder, isn’t little or no ice more common than ice ages in Earth’s history?)

  19. jstahle

    The famous “hockey stick” graph has been infamous for several years.

    Pro-CO2 climate climate scientist from the Danish Meteorological Institute, Copenhagen, Denmark, tested the software and found that different "red noise" data sets produced hockey sticks.

  20. Ea Nassir

    The sun has become old, and it is gradually losing its heat, but this is difficult for observers to decide, because of the tremendous heat of the sun.

    Actually, yes, the sun is losing its heat, and this is a gradual process.

    It is acquiring a membranous and incomplete crust, but the process is proceeding and is in progress.

    This explains many things including the recent change in the solar cycle, its delaying and its weakness.

    The complete cooling of the sun surface will take about 2000 years, after which the sun will burst and break up into 19 pieces (in the next Doomsday.)

  21. Ea Nassir

    You can make google search about these titles:

    The Recent Solar Cycle 24 is the Weakest in 100 Years

    The Sun will tear up, after the ending of its life, and become nineteen pieces

  22. Bruce

    Eric Holcomb and Trane Francks, your points were excellent. Also, in the recent “A Fix for the Faint Young Sun Paradox” newsblog Tom Yelin and Peter made comments that shed light on this conversation as well.
    Tom Yelin wrote: “Kelly writes that the current carbon dioxide concentration is 360 ppm. This is incorrect. It is now 400 ppm (or very nearly that).”
    Peter then wrote: “Observations suggest: delta_T = k*log(CO2), where k is a constant. In other words, if doubling CO2 concentration raises Earth’s temperature 4 degrees, doubling it again will raise it another 4. A warm world is better than a frozen one. On the other hand, thresholds exist, so we are kind of playing with fire.”
    Another reference that was most informative is At the top of this web page under the question “Climate change: how do we know?” a graph is provided showing CO2 levels over the last 400,000 years. It shows the massive spike upward in recent years and confirms that CO2 was (at the time the chart was published) about 383 ppm. If the formula Peter provided is valid then we are already in trouble, because it would take less than a 4 degree global temperature rise to cause significant change in sea level. Before I was as informed on this I was going to say, what, do we have to wait until sea level rise is observed before we believe this can happen, but I see from NASA’s web page that “Global sea level rose about 17cm in the last century. The rate in the last decade, however, is nearly double that of the last century.” Intelligent people can disagree about which factor is the greatest cause, but the fact that global warming is happening is beyond all reasonable doubt.

  23. Peter WilsonPeter

    We will probably see a total melt-down and shift away from glacial coverage resulting in massive sea-level rise, but this will only look like a disaster from out point of view. For sea-life, the 20th century was a disaster. From our using the ocean as a sewer, to farm fertilizer run-off, to shark-finning, but especially due to fossil-fuel powered, refrigerated, factory fishing-vessels ravaging the ocean with the latest fish-finding technology, mankind’s euphoric discovery of fossil fuels has been a disaster for marine life. A recent article describes government plans to kill 100 sharks near an Indian ocean island, because 1 shark killed a 15-year old swimmer. Yeah, that’ll teach ‘em! If sea levels rise 20 meters and drown our coastal cities, as well as a few islands, there will be no sharks weeping over it.

  24. Bruce

    Mankind sure has messed things up, haven’t we Peter. To the things your mentioned acidification of the seas, wide scale deforestation, reduction of biodiversity and other things I’m sure can also be sited. I’m reminded of what an ancient Hebrew prophet once wrote, “It does not belong to man who is walking even to direct his step.” (Jeremiah 10:23) The solutions to these problems are far beyond what man in his much less than infinite wisdom can find. This also reminds me of a prophecy that there would come a time when God would “bring to ruin those ruining the earth.” (Revelation 11:18) Even many who don’t believe that there is a God should be able to see that the Earth is being ruined. I remain hopeful however, due to what Isaiah wrote at Isaiah 45:18, and what Jesus said at Mathew 5:5, “Blessed are the meek: for they shall inherit the earth.”

  25. Walter Horsting

    In the past year 1 million plus farm herd animals buried alive in snow in the UK, Ireland, NZ, Peru, Argentina and now Dakota. Five straight cold winters in the UK is just the start of a steady decline into cycle 25 sun minimum.

    UV radiation which has deeper penetration of the seas has much more radical swings of energy than TSI. Add in Forbush events impacting Cosmic Ray Cloud formation and there is a clear mechanism in solar variation impacting climate on earth.

    With tens of thousands of volcanic underseas vents and volcano the oceans release CO2 when they warm and retain CO2 more when cold. During the last ice age the CO2 in the atmosphere reach near plant life starvation levels. When the earth warms the CO2 follow by about 800 years.

  26. Penelope

    This morning I didn’t even know what a sunspot or solar cycle is, so doubtless my comment is valueless, but I can’t resist.
    If the north and south hemispheres are out of phase with each other– asymmetric–wouldn’t that automatically reduce the magnetic field of the sunspots? I mean, carrying the analogy of the sun to a bar magnet, if you distort the magnet. . . . So if the whole magnetic field is weaker, then the sunspots can’t express it, or draw on it, or whatever. Sorry. Terribly facile.