The Unusually Quiet Sun finally gets some attention

Solar cycle 24 has yet to decisively start, and many metrics show solar activity at unusually low levels.  This potentially important story has begun to get some attention from the media.

  1. ‘Still Sun’ baffling astronomers“, BBC, 21 April 2009
  2. Sun ‘at its quietest for 100 years’“, Press Association (a newswire), 21 April 2009
  3. Has the sun gone in? Earth’s closest star ‘dimmest it’s been for a century’“, Daily Mail, 21 April 2009
  4. A Quiet Sun Doesn’t Happen Overnight“, Charles Osgood, CBS, 21 April 2009
  5. (update) “The missing sunspots: Is this the big chill?“, The Independent, 27 April 2009 — “Scientists are baffled by what they’re seeing on the Sun’s surface – nothing at all. And this lack of activity could have a major impact on global warming.”

It’s a little flurry of stories, all careful to avoid mentioning the strong evidence about the Sun’s influence on Earth’s climate (although the mechanism for this remains unclear).  Perhaps the best summary I’ve seen is this, from NASA’s Earth Observatory page — “The Sun’s Chilly Impact on Earth“, 6 December 2001. Excerpt:

During the coldest part of the Little Ice Age, from 1645 to 1715, there is believed to have been a decrease in the total energy output from the Sun, as indicated by little or no sunspot activity. Known as the Maunder Minimum, astronomers of the time observed only about 50 sunspots for a 30-year period as opposed to a more typical 40-50,000 spots. The Sun normally shows signs of variability, such as its eleven-year sunspot cycle. Within that time, it goes from a minimum to a maximum period of activity represented by a peak in sunspots and flare activity.

Beginning in 1611, Galileo Galilei made drawings of lower sunspot activity before the Maunder Minimum. Records of sunspot activity during the Minimum from other astronomers confirm the lower number of sunspots over the70 year event.

During those periods of low solar activity, levels of the Sun’s ultraviolet radiation decrease, and can significantly impact ozone formation in the stratosphere. “The changes in ozone that we modeled were key in producing the enhanced response,” Shindell said. “The changes in the upper atmosphere then feed down to the surface climate.”

Between the mid-1600s and the early 1700s the Earth’s surface temperatures in the Northern Hemisphere appear to have been at or near their lowest values of the last millennium. European winter temperatures over that time period were reduced by 1.8 to 2.7 degrees Fahrenheit (1-1.5 Celsius). This cool down is evident through derived temperature readings from tree rings and ice cores, and in historical temperature records, as gathered by the University of Massachusetts-Amherst and the University of Virginia.

Solar cycle 24, the next 11 year cycle (they vary in length), has gotten off to a slow start.  There is growing concern about this.  For more information about this see these posts on the FM site about the solar cycle (esp the last one).  If solar activity does not pick up soon, we will see a lot more articles about this.

  1. Worrying about the Sun and climate change: cycle 24 is late, 10 July 2008
  2. Update: is Solar Cycle 24 late (a cooling cycle, with famines, etc)?, 15 july 2008
  3. Solar Cycle 24 is still late, perhaps signalling cool weather ahead, 2 September 2008
  4. Update on solar cycle 24 – and a possible period of global cooling, 1 October 2008
  5. This week’s report on the news in climate science, 7 December 2008
  6. Weekend reading recommenations about climate change, 13 December 2008
  7. An important new article about climate change, 29 December 2008
  8. About the recent conference ”Solar Activity during the onset of Solar Cycle 24″, 3 January 2009
  9. NASA: Sun undergoing a “deep solar minimum”, 13 April 2009

To see a small slice of the scientific literature about the Sun’s influence on Earth’s climate, see section 4 — The Solar Cycle — on the FM reference page Science & nature – studies & reports.


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8 thoughts on “The Unusually Quiet Sun finally gets some attention”

  1. Also in the popular press was “A Quiet Sun Doesn’t Happen Overnight“, Charles Osgood, CBS, 21 April 2009 — Excerpt:

    I know you’ve already got a lot to worry about as it is, but something rather odd is going on — on the Sun. The Sun normally undergoes an 11-year cycle of activity — and last year, it was supposed to have heated up — and, at its peak, would have a tumultuous boiling atmosphere, spitting out flares and huge chunks of super-hot gas.

    Instead, it hit a 50-year low in solar wind pressure, a 55-year low in radio emissions, and a 100-year low in sunspot activity. Right now, the sun is the dimmest it’s been in nearly a century.
    Did you know that? It’s true. Astronomers are baffled by it, but has the press covered the story? Hardly at all. Is the government doing anything about it? No, it’s not even in the Obama budget or any Congressional earmarks.

    Right now, global warming is a given to so many, it raises the question: Could another minimum activity period on the Sun counteract, in any way, the effects of global warming?

    FM Note: I have added this to the post. Thanks!

  2. Well, we wouldn’t want to upset the apple cart regarding the dogmatic observance of AGW, now would we?

  3. We should be grateful. Human civilization has become increasingly dependent on man made satellites in the last ten years. A solar storm could short out our sat infrastructure! On the other hand this could be the calm before the storm. We should use this blessing to develop the next generation of hardened satellites.

  4. And check out this story: “Sunspots reaching 1,000-year high“, BBC, 6 July 2004 — Excerpt:

    Scientists based at the Institute for Astronomy in Zurich used ice cores from Greenland to construct a picture of our star’s activity in the past. They say that over the last century the number of sunspots rose at the same time that the Earth’s climate became steadily warmer.

    The variation in sunspot numbers has revealed the Sun’s 11-year cycle of activity as well as other, longer-term changes. In particular, it has been noted that between about 1645 and 1715, few sunspots were seen on the Sun’s surface. This period is called the Maunder Minimum after the English astronomer who studied it. It coincided with a spell of prolonged cold weather often referred to as the “Little Ice Age”. Solar scientists strongly suspect there is a link between the two events – but the exact mechanism remains elusive.

    Over the past few thousand years there is evidence of earlier Maunder-like coolings in the Earth’s climate – indicated by tree-ring measurements that show slow growth due to prolonged cold.

    In an attempt to determine what happened to sunspots during these other cold periods, Dr Sami Solanki and colleagues have looked at concentrations of a form, or isotope, of beryllium in ice cores from Greenland.

    .. But the most striking feature, he says, is that looking at the past 1,150 years the Sun has never been as active as it has been during the past 60 years. Over the past few hundred years, there has been a steady increase in the numbers of sunspots, a trend that has accelerated in the past century, just at the time when the Earth has been getting warmer.

    The data suggests that changing solar activity is influencing in some way the global climate causing the world to get warmer.

    FM Note: The paper described here isSolar Activity Over the Last 1150 Years: Does it Correlate with Climate?“, Usoskin I.G., Schussler M., Solanki S.K., Mursula K., In Proceedings of The 13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun”, F. Favata, G.A.J. Hussain, B. Battrick (Eds.), ESA SP-560, ESA Publ. Div., Noordwijk, p. 19-22 (2005).

  5. All normal stars are variable to various degrees, some extremely so. There is the obvious relationship of solar output to surface temperatures – more light equals more heat – but there are certainly complexities in the relationship.

    As others have noted before, our greatest asset is adaptability. It’s gotten our species through Ice Ages before!
    Fabius Maximus replies: Climate science seldom works in obvious ways. The largest forcing from increased CO2 is not a CO2 based greenhouse effect (instead it is a multiplier, as slight warming from CO2 increases humidity — and water vapor is a more potent greenhouse gas). Similarly, the Sun’s influence on Earth’s temperature is perhaps not direct heating from increased Total Solar Irradiance — but other effects (such as changes in Earth’s magnetosphere, allowing in more cosmic rays, which increase clouds, cooling the Earth). This is all on the edge of current science.

  6. The lower level of solar activity is exerting a cooling influence on the earth. Could that cause the flattening of global temperature averages this decade? I.e., could “solar cooling” be masking the greenhouse effect? If so, the sun is effectively buying time for us to move to sustainable energy practices. Thank you, Sun!

    Solar activity will someday return to normal. When that happens, won’t average temperatures rise significantly? How can these solar effects contribute to falsifying the AGW hypothesis?
    Fabius Maximus replies: (1) It goes to the current uncertainty about the relative effect of various forcings over all time frames. Hence primarily-CO2-based explanations are a theory, as yet unproven to a degree reliable for large-scale public policy purposes. For example, a statistical case can be made on statistical grounds that solar activity explains much of the past century of so warming, although the actual dynamics (if any) are at best poorly understood. For a brief intro, see the website of the Active Cavity Radiometer Irradiance Monitor Satellite project.

    (2) “The lower level of solar activity is exerting a cooling influence on the earth.”

    At present that’s a theory, not a fact (if you mean this in a non-trival sense).

    (3) “How can these solar effects contribute to falsifying the AGW hypothesis?”

    At the very least, it can change the timeframe over which solutions can be implemented. For example, it might falsify James Hansen’s warning that “Obama has only four years to save the world” (Interview in The Obsever, 18 January 2009).

  7. Another quiet sun story

    The missing sunspots: Is this the big chill?“, Dr David Whitehouse, The Independent, 27 April 2009 — “Scientists are baffled by what they’re seeing on the Sun’s surface – nothing at all. And this lack of activity could have a major impact on global warming.” Excerpt:

    Could the Sun play a greater role in recent climate change than has been believed? Climatologists had dismissed the idea and some solar scientists have been reticent about it because of its connections with those who those who deny climate change. But now the speculation has grown louder because of what is happening to our Sun. No living scientist has seen it behave this way. There are no sunspots.

    The disappearance of sunspots happens every few years, but this time it’s gone on far longer than anyone expected – and there is no sign of the Sun waking up. “This is the lowest we’ve ever seen. We thought we’d be out of it by now, but we’re not,” says Marc Hairston of the University of Texas. And it’s not just the sunspots that are causing concern. There is also the so-called solar wind – streams of particles the Sun pours out – that is at its weakest since records began. In addition, the Sun’s magnetic axis is tilted to an unusual degree. “This is the quietest Sun we’ve seen in almost a century,” says NASA solar scientist David Hathaway. But this is not just a scientific curiosity. It could affect everyone on Earth and force what for many is the unthinkable: a reappraisal of the science behind recent global warming.

    … Many scientists believe that the Sun was the major player on the Earth’s climate until the past few decades, when the greenhouse effect from increasing levels of carbon dioxide overwhelmed it.

    Computer models suggest that of the 0.5C increase in global average temperatures over the past 30 years, only 10-20 per cent of the temperature variations observed were down to the Sun, although some said it was 50 per cent.

    But around the turn of the century things started to change. Within a few years of the Sun’s activity starting to decline, the rise in the Earth’s temperature began to slow and has now been constant since the turn of the century. This was at the same time that the levels of atmospheric carbon dioxide carried on rising. So, is the Sun’s quietness responsible for the tail-off in global warming and if not, what is?

    There are some clues as to what’s going on. Although at solar maxima there are more sunspots on the Sun’s surface, their dimming effect is more than offset by the appearance of bright patches on the Sun’s disc called faculae – Italian for “little torches”. Overall, during an 11-year solar cycle the Sun’s output changes by only 0.1 per cent, an amount considered by many to be too small a variation to change much on earth. But there is another way of looking it. While this 0.1 per cent variation is small as a percentage, in terms of absolute energy levels it is enormous, amounting to a highly significant 1.3 Watts of energy per square metre at the Earth. This means that during the solar cycle’s rising phase from solar minima to maxima, the Sun’s increasing brightness has the same climate-forcing effect as that from increasing atmospheric greenhouse gasses. There is recent research suggesting that solar variability can have a very strong regional climatic influence on Earth – in fact stronger than any man-made greenhouse effect across vast swathes of the Earth. And that could rewrite the rules.

    No one knows what will happen or how it will effect our understanding of climate change on Earth. If the Earth cools under a quiet Sun, then it may be an indication that the increase in the Sun’s activity since the Little Ice Age has been the dominant factor in global temperature rises. That would also mean that we have overestimated the sensitivity of the Earth’s atmosphere to an increase of carbon dioxide from the pre-industrial three parts per 10,000 by volume to today’s four parts per 10,000. Or the sun could compete with global warming, holding it back for a while. For now, all scientists can do, along with the rest of us, is to watch and wait.

    Dr David Whitehouse is author of The Sun: A Biography (John Wiley)

  8. Agree that all my assertions are merely hypotheses.

    Agree that apocalyptics like Hansen aren’t helping anything. If we have only four years, it’s over.

    However, it wouldn’t surprise me if the sun returned to normal very quickly, and it further wouldn’t surprise me if the masking effect was significant, leading to a return to the rising temp trend of prior decades. Hope I’m wrong.
    Fabius Maximus replies: It’s not possible to talk sensibly about climate on this level. Even were we both climate scientists, there is inadequate basis for reliable forecasts at this time. So guesses — “surprise” and “hope” — do little for us. More and much better research is needed. And time.

    (1) There is no yet substantial evidence that the sun is abnormal. Note the articles cited on these posts:
    * News from the conference on “Solar Activity during the onset of Solar Cycle 24″, 3 January 2009
    * NASA: Sun undergoing a “deep solar minimum”, 13 April 2009

    (2) There is no consensus among relevant experts as to the length and magnitude of solar cycle 24. See “Cycle 24 predictions summary“, website of the Solar-Stellar Spectrograph project, 4 March 2009.

    (3) There is no consensus on the degree of solar influence on Earth’s climate over most time scales, and even less on the mechanisms.

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