A grand solar minimum would barely make a dent in human-caused global warming

Research has shown that a grand solar minimum would offset no more than 0.3 °C of global warming

by Dana Nuccitelli, "Climate Consensus - The 97%," The Guardian, January 19, 2014

Fortunately for us, solar activity is quite stable, and a solar minimum would only have a small effect on global temperatures. Photograph: saesnes

Recent articles in the Danish newspaper Jyllands-Posten (translation available here) and in the Irish Times both ran headlines claiming that another grand solar minimum could potentially trigger an "ice age" or "mini ice age" this century. These articles actually refer to the Little Ice Age (LIA) – a period about 500 to 150 years ago when global surface temperatures were approximately 1 °C colder than they are today. This is quite different from an ice age, which are more like 5m°C colder than today. The LIA was not actually very cold on a global scale.

So, in order to trigger another LIA, a new grand solar minimum would have to cause about 1 °C cooling, plus it would have to offset the continued human-caused global warming of 1 to 5 °C by 2100, depending on how our greenhouse gas emissions change over the next century.

In the Jyllands-Posten article, Henrik Svensmark (the main scientist behind the hypothesis that the sun has a significant indirect impact on global climate via galactic cosmic rays) was a bit more measured, suggesting,

"I can imagine that it will become 0.2 °C colder. I would be surprised if it became 1–2 °C"

So these two articles are suggesting that a grand solar minimum could have a net cooling effect in the ballpark of 1 to 6 °C, depending on how human greenhouse gas emissions change over the next century. Is it plausible that a grand solar minimum could make that happen?

The short answer is, 'No.'

Fortunately, Solar Output is Stable

We're fortunate that the amount of solar radiation reaching the Earth's surface is very stable. Climate contrarians will often ask if we'd prefer if the planet were warming or cooling, suggesting that global warming is a good thing because at least the planet isn't getting colder. This is a false dichotomy - an ideal climate is a stable one.

The relatively stable climate over the past 10,000 years has allowed establishment of human civilization, by making it possible to create large stationary agricultural farms because we could rely on stable weather patterns. During that time, net global surface temperatures changes haven't exceeded 1 °C from the coldest to the hottest climates, though we're now approaching that degree of change, with 1 °C warming since the LIA, 0.8 °C of that over the past century, with much more to come.

What difference would a grand solar minimum make in the amount of solar energy reaching Earth? Two examples are the Maunder Minimum, a period of very low solar activity between 1645 and 1715, and the Dalton Minimum, a period of low (but not as low as the Maunder Minimum) solar activity between 1790 and 1830.

400 years of sunspot observations data. Created by Robert Rohde, via Wikipedia.

Relative to current levels, the Dalton Minimum represents a 0.08% decrease in the amount of solar radiation reaching the Earth's surface, and the Maunder Minimum represents a 0.25% decline. That's how stable solar activity is. That's also why we're playing with fire by increasing the greenhouse effect so much and so quickly. We're threatening the stability of the climate that has been so favorable to our development.

Peer-Reviewed Research Says Global Warming will Continue

There have been several studies in recent years investigating what impact another grand solar minimum would have on global surface temperatures, since solar research suggests it's possible we could be due for another extended solar minimum. Generally these studies will run climate model simulations under a given greenhouse gas emissions scenario with stable solar activity, then run the same scenario with the sun going into a grand minimum, and look at the difference in resulting global surface temperature changes.

Using this approach, Feulner and Rahmstorf (2010) (PDF available here) estimated that another solar minimum equivalent to the Dalton and Maunder Minima would cause 0.09 °C and 0.26 °C cooling, respectively.

The global mean temperature difference is shown for the time period 1900 to 2100 for the IPCC A2 emissions scenario. The red line shows predicted temperature change for the current level of solar activity, the blue line shows predicted temperature change for solar activity at the much lower level of the Maunder Minimum, and the black line shows observed temperatures through 2010. Adapted from Feulner & Rahmstorf (2010) by SkepticalScience.com

Jones et al. (2012) (PDF available here) arrived at a nearly identical result, with cooling from another Dalton or Maunder Minimum at 0.09 °C and 0.26 °C, respectively. Similarly, a new paper by Anet et al. (2013) found that a grand solar minimum will cause no more than 0.3 °C cooling over the 21st century.

Consistent with these previous studies, Meehl et al. (2013) (PDF available here) estimate a Maunder Minimum would cause about 0.26 °C cooling, but as soon as solar activity began to rise again, that cooling would be offset by solar warming. This is a key point, because a grand solar minimum would not be a permanent change. These solar minima last for a few decades, but eventually solar activity rises once again. Thus any cooling caused by a solar minimum would only be temporary.

The cooling effect of a grand solar minimum can also be estimated very easily without the aid of climate models, because the change in the amount of solar radiation reaching the Earth's surface is directly proportional to the temperature change it causes. Performing this calculation yields the same result as the model-based research: approximately 0.3 °C cooling from another Maunder-type grand solar minimum. Click here to see the details behind the calculation.

The Heating of the Deep Oceans

In the Jyllands-Posten article, Svensmark also disputes the data showing the accelerated accumulation of heat in the deep oceans.

"How can the ocean below 700 meters be heated up, without the upper ocean warming up accordingly?"

This is an increasingly common argument made by climate contrarians, and a bit of a strange one. The data are what they are - we've measured the deep ocean warming, including with reliable instruments on Argo buoys for close to a decade now. Even if we couldn't explain how the heat got there, it's there.

5-year averages of ocean heat content 0-700 meters (red) and 0-2000 meters (black), from the National Oceanographic Data Center

But let's address the question anyway - do we expect to have seen some obvious indication of heat being transferred from the shallow to deep ocean layers?

It's certainly not clear that we should. Consider the analogy of a bathtub. Water from the faucet represents heat entering the shallow ocean layer. Water exiting the drain represents heat leaving the shallow oceans and entering the deep oceans. The water level in the bathtub represents the heat in the shallow ocean layer (which is what we measure).

If the amount of water entering the tub from the faucet is the same as the amount of water draining out of the tub, the water level in the tub won't change. Yet the water still flows down the drain. Climate scientist Gavin Schmidt has discussed this point, summarized here.

In short, we wouldn't necessarily see the heat being transferred through the shallow to the deep oceans. However, there has been plenty of warming of the shallow oceans that could have been transferred to the deeper oceans. In our case, the water is flowing into the tub faster than it's draining out - the shallow oceans are warming fast, as the figure above illustrates.

Svensmark Gets Ocean Warming Wrong

Unfortunately Svensmark appears to be unfamiliar with this ocean heating data, saying,

"The thousands of buoys that we have deployed after 2003 to measure the ocean temperature, have not registered any temperature rise."

This is just totally wrong, even if we ignore the rapid warming of the deep oceans (as is clear from a simple examination of the figure above). The ocean heat content data can be downloaded from the National Oceanographic Data Center here. The heating trend since 2003 in the upper 700 meters of oceans is equivalent to nearly 1 Hiroshima atomic bomb detonation per second (plus another 3 per second in the deep oceans). Both the shallow and deep oceans are accumulating a whole lot of heat, with no signs of slowing whatsoever. If anything, the heating of the oceans and the planet as a whole is accelerating.

Human Influence on Climate Change is Bigger than the Sun's

The bottom line is that the sun and the amount of solar radiation reaching Earth are very stable. Even during the Maunder and Dalton grand solar minima, global cooling was relatively small - smaller than the amount of global warming caused by human greenhouse gas emissions over the past century.

A new grand solar minimum would not trigger another LIA; in fact, the maximum 0.3°C cooling would barely make a dent in the human-caused global warming over the next century. While it would be enough to offset to about a decade's worth of human-caused warming, it's also important to bear in mind that any solar cooling would only be temporary, until the end of the solar minimum.

The science is quite clear that the human influence on climate change has become bigger than the sun's. At this point, speculation about another mini ice age is pure fantasy.

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2013/aug/14/global-warming-solar-minimum-barely-dent

"Small influence of solar variability on climate over the past millennium, by A.P. Schurer, S.F.B. Tett & G.C. Hegerl, Nature Geosci. (2013); doi: 10.1038/ngeo2040

Nature Geoscience, (22 December 2013); doi: 10.1038/ngeo2040

Small influence of solar variability on climate over the past millennium

• Andrew P. Schurer,
• Simon F. B. Tett and
•  Gabriele C. Hegerl

Abstract

The climate of the past millennium was marked by substantial decadal and centennial scale variability in the Northern Hemisphere¹. Low solar activity has been linked to cooling during the Little Ice Age (AD 1450–1850; ref.  1) and there may have been solar forcing of regional warmth during the Medieval Climate Anomaly^{2, 3, 4, 5} (AD 950–1250; ref. 1). The amplitude of the associated changes is, however, poorly constrained^5, 6, with estimates of solar forcing spanning almost an order of magnitude^7, 8, 9. Numerical simulations tentatively indicate that a small amplitude best agrees with available temperature reconstructions^{10, 11, 12, 13}. Here we compare the climatic fingerprints of high and low solar forcing derived from model simulations with an ensemble of surface-air-temperature reconstructions¹⁴ for the past millennium. Our methodology¹⁵ also accounts for internal climate variability and other external drivers such as volcanic eruptions, as well as uncertainties in the proxy reconstructions and model output. We find that neither a high magnitude of solar forcing nor a strong climate effect of that forcing agree with the temperature reconstructions. We instead conclude that solar forcing probably had a minor effect on Northern Hemisphere climate over the past 1,000 years, while, volcanic eruptions and changes in greenhouse gas concentrations seem to be the most important influence over this period.

Link:  http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2040.html

MORE MUST READ TIDBITS: Kevin Trenberth on ocean heat content, changing trade winds, mechanism for heat to be carried down deeper in the ocean

Global warming is here to stay, whichever way you look at it

by Kevin Trenberth, University Corporation for Atmospheric Research, The Conversation, May 22, 2013

Has global warming stalled? This question is increasingly being asked because the local weather seems cool and wet, or because the global mean temperature is not increasing at its earlier rate or the long-term rate expected from climate model projections.

The answer depends a lot on what one means by “global warming.” For some it is equated to the “global mean temperature.” That keeps going up but also has ups and downs from year to year. More on that shortly.

Why should it go up? Well, because the planet is warming as a result of human activities. With increasing carbon dioxide and other heat-trapping greenhouse gases in the atmosphere, there is an imbalance in energy flows in and out of the top of the atmosphere: the greenhouse gases increasingly trap more radiation and hence create warming. “Warming” really means heating, and this can exhibit itself in many ways.

Rising surface temperatures are just one manifestation. Melting Arctic sea ice is another. So is melting of glaciers and other land ice that contribute to rising sea levels. Increasing the water cycle and invigorating storms is yet another. But most (more than 90%) of the energy imbalance goes into the ocean, and several analyses have now shown this. But even there, how much warms the upper layers of the ocean, as opposed to how much penetrates deeper into the ocean where it may not have much immediate influence, is a key issue.

The ups and downs of global temperature

My colleagues and I have just published a new analysis showing that in the past decade about 30% of the heat has been dumped at levels below 700 meters, where most previous analyses stop.

The first point is that this is fairly new; it is not there throughout the record. The cause of the shift is a particular change in winds, especially in the Pacific Ocean where the subtropical trade winds have become noticeably stronger, changing ocean currents and providing a mechanism for heat to be carried down into the ocean. This is associated with weather patterns in the Pacific, which are in turn related to the La Niña phase of the El Niño phenomenon.

The second point is that we have found distinctive variations in global warming with El Niño. A mini global warming, in the sense of a global temperature increase, occurs in the latter stages of an El Niño event, as heat comes out of the ocean and warms the atmosphere. The ocean’s temperature is also affected by volcanic eruptions, which also affect the perceptions of global warming.

Normal weather also interferes by generating clouds that reflect the sunshine, and there are fluctuations in the global energy imbalance from month to month. But these average out over a year or so.

Another prominent source of natural variability in the Earth’s energy imbalance is changes in the sun itself, seen most clearly as the sunspot cycle. From 2005 to 2010 the sun went into a quiet phase and the warming energy imbalance is estimated to have dropped by about 10 to 15%.

Some of the penetration of heat into the depths of the ocean is reversible, as it comes back in the next El Niño [whenever that is -- no signs of one for the rest of this year]. But a lot is not; instead it contributes to the overall warming of the deep ocean. This means less short-term warming at the surface, but at the expense of greater long-term warming, and faster sea level rise. So this has consequences.

Global warming is here to stay

Coming back to the global temperature record, one thing is clear. The past decade is by far the warmest on record. Human-induced global warming really kicked in during the 1970s, and warming has been pretty steady since then.

While the overall warming is about 0.16 °C per decade, there are three 10-year periods where there was a hiatus in warming, as the graph above shows, from 1977 to 1986, from 1987 to 1996, and from 2001 to 2012. But at each end of these periods there were big jumps. We find exactly the same sort of flat periods in climate model projections, lasting easily up to 15 years in length.

Focusing on the wiggles and ignoring the bigger picture of unabated warming is foolhardy, but an approach promoted by climate change deniers. Global sea level keeps marching up at a rate of more than 30 cm per century since 1992 (when global measurements via altimetry on satellites were made possible), and that is perhaps a better indicator that global warming continues unabated. Sea level rise comes from both the melting of land ice, thus adding more water to the ocean, plus the warming and thus expanding ocean itself.

Global warming is manifested in a number of ways, and there is a continuing radiative imbalance at the top of atmosphere. The current hiatus in surface warming is temporary, and global warming has not gone away.

Kevin Trenberth does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.


This article was originally published at The Conversation. Read the original article.

http://theconversation.com/global-warming-is-here-to-stay-whichever-way-you-look-at-it-14532

Stefan Rahmstorf: If 2013 breaks heat record, how will deniers respond?

by Stefan Rahmstorf, New Scientist, No. 2880, September 3, 2012

With an El Niño on the way, 2013 could be the warmest year on record. 

But the climate-denial machine will keep on churning

It has been another "normal" global-warming summer in the northern hemisphere. The US sweltered in the hottest July on record, following the hottest spring on record. More than 60% of the contiguous US is suffering from drought, as are parts of eastern Europe and India. In the Arctic, sea ice cover is at a record low and the Greenland ice sheet shows what the US National Snow and Ice Data Center calls "extraordinary high melting." Global land temperatures for May and June were the hottest since records began in the 19th century.

Meanwhile, El Niño conditions are forecast to develop in the tropical Pacific Ocean, warming up ocean surface temperatures. Some observers have predicted that this will lead to record-breaking global temperatures next year.

If El Niño does arrive and temperature records are broken, there will inevitably be much discussion of the causes of the warming. So now is a good time to sort signal from noise in the global temperature records.

For the past 30 years, global temperature has shown a linear warming trend of 0.16 °C per decade (Environmental Research Letters, Vol. 6, p. 044022). When looking for the cause of this warming, a physicist will look for the heat source. One possibility is that the oceans are releasing heat. But measurements show the opposite: the oceans are soaking up heat. The other possibility is that the heat is coming from above, and indeed it is: more radiation is entering the top of the atmosphere than leaving it. This is because increasing amounts of greenhouse gases in the atmosphere hamper the loss of heat into space.

Superimposed on this global-warming signal is short-term natural variability, which makes some years hotter and some colder. Some, notably 2005 and 2010, stick out above the trend line, whereas others, like 2008 and 2011, stay below it. But overall, temperatures are creeping upwards within a corridor of plus or minus 0.2 °C around the trend line. Climate deniers use this variability to claim there is a slowdown in global warming, by cherry-picking time intervals that happen to start in the upper part of the corridor and end in the lower. They mix up signal and noise.

Three known factors explain much of the natural variation. The first is volcanic eruptions -- the eruption of Mount Pinatubo in the Philippines in 1991 was followed by three cold years, for example. Then there is the sun's variability, mostly in the form of the 11-year sunspot cycle. Finally, there is the irregular oscillation between warm El Niño and cold La Niña conditions in the Pacific.

We have independent measurements describing all three that we can easily correlate to global temperature changes. This shows, for example, that during a solar maximum the globe is about 0.1 °C warmer than during a solar minimum, but also that solar activity has contributed nothing to the warming trend of the past 30 years. In fact, it has acted to reduce it, but the effect is so small that the hottest year on record, 2010, was near the end of the deepest solar minimum since satellite measurements began in the 1970s.

The analysis further shows that global temperature typically reaches a maximum about four months after El Niño conditions peak, and is correspondingly colder after La Niña. La Niña episodes in 2008 and 2011 have cooled the past few years, masking the warming trend. But while 2011 was cool in the context of the previous 10 years, it was the hottest La Niña year on record.

It is straightforward to remove the effects of the solar and El Niño cycles from the data, just as unemployment figures routinely have seasonal effects removed. Once this is done, and regardless of the global temperature dataset used, the result is always a steady warming trend that has been no slower in the past decade than it was in the previous two -- and which, incidentally, agrees with what is predicted by the Intergovernmental Panel on Climate Change.

Now solar activity is on the way back up and it is only a matter of time before the next El Niño event comes along. In fact, predictions by the US National Oceanic and Atmospheric Administration suggest that El Niño conditions are likely to arrive any time now. These two factors, combined with the ongoing warming trend, make it likely that a global temperature record will be set next year -- unless a major volcano erupts.

Perhaps a record year will silence those unscientific voices who claim that global warming has come to an end. But the denial industry has already come up with a plan B: to claim that global warming is completely down to El Niño. To expose the fallacy of that, we just need to look again at where the heat comes from: below or above.

In the case of El Niño, the warmth comes from the ocean. During El Niño events, the global ocean releases heat, whereas during La Niña events, it recharges its heat store. That is confirmed by satellite measurements of the radiation balance: during recent La Niña events our planet did not lose heat to space. On the contrary, it absorbed more than normal. That is to be expected: when the ocean exposes colder waters at its surface, as during La Niña, these soak up extra heat.

So if global warming of the past decades was due to El Niño or another mechanism involving heat from the ocean, the ocean would have lost heat. But the heat content has gone up, not down. And it is well understood why: because we created a radiation imbalance by adding greenhouse gases to our atmosphere.

The signal of global warming caused by humans is very clear, despite attempts by certain parties to drown it out with a lot of noise.

Stefan Rahmstorf heads the Earth System Analysis department at the Potsdam Institute for Climate Impact Research in Germany. He is coauthor of The Climate Crisis (Cambridge University Press, 2009)

http://www.newscientist.com/article/mg21528804.400-if-2013-breaks-heat-record-how-will-deniers-respond.html

Peter Sinclair: Myth of the Mini Ice Age [Climate Denial Crock of the Week]

Climate Denial Crock of the Week by Peter Sinclair:  Myth of the Mini Ice Age

http://www.youtube.com/watch?v=IQHqgdvXTxE

What if the Sun went into a new Grand Minimum? Guest commentary by Georg Feulner, Real Climate, June 19, 2011

What if the Sun went into a new Grand Minimum?

Guest commentary by Georg Feulner, Real Climate, June 19, 2011

During a meeting of the Solar Physics Division of the American Astronomical Society, solar physicists have just announced a prediction that the Sun might enter an extended period of low activity (a ‘grand minimum’) similar to the Maunder Minimum in the 17th century. In this post I will explore the background of this announcement and discuss implications for Earth’s climate.

It has been known for a long time that solar activity shows a very regular pattern. Every 11 years the Sun is particularly active, and numerous dark sunspots are visible on its surface. These maxima of solar activity are separated by times of low activity when only few (if any) sunspots appear.

Figure 1: The Sun in visible light during an activity maximum (left) and during the last (and rather extraordinary) 11-year minimum during which it appeared spotless most of the time. Source: NASA Earth Observatory/SOHO.

One could think that the Sun emits less light during a solar maximum because of the many dark spots. In fact it is the other way round, since active regions around the sunspots emit more radiation than is “lost” in the cooler sunspot areas. This effect can be best seen in ultraviolet images of the Sun.

Figure 2: The Sun in ultraviolet light during a maximum (left) and a minimum (right). Source: NASA Earth Observatory/SOHO.

An analysis of historic sunspot observations shows that the 11-year solar activity cycle was interrupted during the late 17th century.

This period of time, during which the Sun appeared without sunspots most of the time, was called the Maunder Minimum by Jack Eddy in his famous Science paper. (Alliteratively named after Edward Maunder, although it was actually first discovered by Gustav Spörer.)

Figure 3: Observations of the number of sunspots over the last four centuries. Source: Wikimedia Commons/Global Warming Art.

The Maunder Minimum falls within the climatically cooler period of the “Little Ice Age,” during which temperatures were particularly low over continents in the Northern hemisphere (especially in winter). It has long been suspected that the low solar activity during the Maunder Minimum was one of the causes of the Little Ice Age, although other factors like a small drop in greenhouse gas concentrations around 1600 and strong volcanic eruptions during that time likely played a role as well.

Solar physicists do not yet understand how an extended solar-activity low like the Maunder Minimum arises. Yet there is recent observational evidence for an unusual behavior of the Sun during the current cycle 24, including a missing zonal wind flow within the Sun, decreasing magnetic field strength of sunspots and lower activity around the poles of the Sun. 

These observations prompted Frank Hill and colleagues to suggest that the Sun might enter a new Maunder-like minimum after the current 11-year cycle ends (i.e., after 2020 or so).

It remains to be seen whether this prognosis turns out to be true (there have been some doubts expressed), but since grand minima of solar activity did occur in the past, it is certainly interesting to explore what effects such a minimum might have on 21st century climate if it did occur. This is precisely the question Stefan Rahmstorf and I investigated in a study published last year (see also our press release. (Earlier estimates for the size of this effect can be found here and here.) In our study we find that a new Maunder Minimum would lead to a cooling of 0.3 °C in the year 2100 at most – relative to an expected anthropogenic warming of around 4 °C. (The amount of warming in the 21st century depends on assumptions about future emissions, of course).

Figure 4: Rise of global temperature (relative to 1961-1990) until the year 2100 for two different emission scenarios (A1B, red; A2, magenta). The dashed lines show the slightly reduced warming in case a Maunder-like solar minimum should occur during the 21st century. Source: PIK.

According to these results, a 21st-century Maunder Minimum would only slightly diminish future warming. Moreover, it would be only a temporary effect since all known grand solar minima have only lasted for a few decades. Critics of this result might argue that the solar forcing in these experiments is only based on the estimated change in total irradiance, which might be an underestimate, or that does not include potential indirect amplifying effects (via an ozone response to UV changes, or galactic cosmic rays affecting clouds). However, our model reproduces the historic Maunder minimum with these estimates of solar irradiance. 

Furthermore, even if one multiplied the solar effects by a huge factor of 5 (which is unrealistic), no absolute cooling would take place (the temperatures would be temporarily cooler than the base scenario, but the trends would still be warming).

It is clear that if a grand minimum were to happen it would be a tremendously exciting opportunity for solar physicists, however it is unlikely to be very exciting for anyone else.

Update 23 June: Here is a nice tongue-in-cheek video on the media response to this story.

http://www.realclimate.org/index.php/archives/2011/06/what-if-the-sun-went-into-a-new-grand-minimum/#more-7928

The average influence of decadal solar forcing on the atmosphere in the South Pacific region by Harry van Loon & Gerald A. Meehl, Geophys. Res. Lett., 38 (2011)

Geophysical Research Letters, 38 (2011) L12804; doi: 10.1029/2011GL047794

The average influence of decadal solar forcing on the atmosphere in the South Pacific region

Key Points

• Anomalously high sea-level pressure in the South Pacific at solar peaks
• The SPCZ is poleward shifted across the entire South Pacific at solar peaks
• The signal in SLP in the South Pacific for solar peaks is different from La Nina

Harry van Loon

Colorado Research Associates, Northwest Research Associates, and the National Center for Atmospheric Research, Boulder, CO, U.S.A. 

and 

Gerald A. Meehl

National Center for Atmospheric Research, Boulder, CO, U.S.A.

Abstract

Composite mean difference analyses are applied to historical sea level pressure (SLP) and sea surface temperature (SST) data to investigate the spatial dependence of the Pacific climate system response to 11-year solar forcing. Previous work has found that the SST and SLP responses are most clearly detected near the times of sunspot maxima, which occur as much as two years prior to the centers of the broad decadal solar cycle maxima. In January–February, the SLP response at sunspot maximum is nearly the same on either side of the equator, although the amplitude is larger in the winter hemisphere. The solar influence is seen as above normal SLP in the sub-Arctic Pacific, as found previously, and as corresponding positive SLP anomalies in the sub-Antarctic Pacific, as shown here for the first time. These SLP anomalies are associated with previously documented signals at sunspot maxima of greater ocean upwelling and cooling along the Pacific equator, and a poleward extension of the tropical convergence zones in both hemispheres. Previous studies using multiple linear regression methods show the broad decadal solar maxima being associated with the lagged warm response in equatorial Pacific SSTs seen in the composites, which is not inconsistent with the present results. In the South Pacific Ocean, the solar effect is visible in the southern summer in the year before the sunspot number peak. The SST and SLP anomalies in the South Pacific in the solar peaks differ markedly from those in Cold Events (La Niña events) of the Southern Oscillation.

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Figure 1 of 3

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Received 13 April 2011; accepted 13 May 2011; published 25 June 2011.

Citation: van Loon, H., and G. A. Meehl (2011), The average influence of decadal solar forcing on the atmosphere in the South Pacific region, Geophys. Res. Lett., 38, L12804, doi:10.1029/2011GL047794.


http://www.agu.org/pubs/crossref/2011/2011GL047794.shtml

National Solar Observatory Press Release; "What's Down with the Sun? Major Drop in Solar Activity Predicted"; Dr. Frank Hill says "We are NOT predicting a mini-ice age..."

National Solar Observatory What's Down with the Sun? Major Drop in Solar Activity Predicted [Dr. Frank Hill: "We are NOT predicting a mini-ice age."]

---

THE FOLLOWING RELEASE WAS RECEIVED JOINTLY FROM THE NATIONAL SOLAR OBSERVATORY IN SUNSPOT, NEW MEXICO, AND THE SOLAR PHYSICS DIVISION OF THE AMERICAN ASTRONOMICAL SOCIETY AND IS FORWARDED FOR YOUR INFORMATION (FORWARDING DOES NOT IMPLY ENDORSEMENT BY THE AMERICAN ASTRONOMICAL SOCIETY). Rick Fienberg, AAS Press Officer: rick.fienberg@aas.org, +1 202-328-2010 x116.** This release was previously distributed to journalists under an embargo that has since expired. {RTF} **
June 14, 2011
Contacts:
Dave Dooling
NSO Education and Public Outreach
+1 575-434-7015 (office); +1 575-921-8736 (cell)
dooling@nso.edu
Craig DeForest
AAS/SPD Press Officer
+1 303-641-5679 (cell)
deforest@boulder.swri.edu
Text & Images: http://www.boulder.swri.edu/~deforest/SPD-sunspot-release

WHAT'S DOWN WITH THE SUN?
MAJOR DROP IN SOLAR ACTIVITY PREDICTED

A missing jet stream, fading spots, and slower activity near the poles say that our Sun is heading for a rest period even as it is acting up for the first time in years, according to scientists at the National Solar Observatory (NSO) and the Air Force Research Laboratory (AFRL).


As the current sunspot cycle, Cycle 24, begins to ramp up toward maximum, independent studies of the solar interior, visible surface, and the corona indicate that the next 11-year solar sunspot cycle, Cycle 25, will be greatly reduced or may not happen at all.


The results were announced at the annual meeting of the Solar Physics Division of the American Astronomical Society, which is being held this week at New Mexico State University in Las Cruces: http://astronomy.nmsu.edu/SPD2011/

"This is highly unusual and unexpected," Dr. Frank Hill, associate director of the NSO's Solar Synoptic Network, said of the results. "But the fact that three completely different views of the Sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation."


Spot numbers and other solar activity rise and fall about every 11 years, which is half of the Sun's 22-year magnetic interval since the Sun's magnetic poles reverse with each cycle. An immediate question is whether this slowdown presages a second Maunder Minimum, a 70-year period with virtually no sunspots during 1645-1715.


Hill is the lead author on one of three papers on these results being presented this week. Using data from the Global Oscillation Network Group (GONG) of six observing stations around the world, the team translates surface pulsations caused by sound reverberating through the Sun into models of the internal structure. One of their discoveries is an east-west zonal wind flow inside the Sun, called the torsional oscillation, which starts at mid-latitudes and migrates towards the equator. The latitude of this wind stream matches the new spot formation in each cycle, and successfully predicted the late onset of the current Cycle 24.
"We expected to see the start of the zonal flow for Cycle 25 by now," Hill explained, "but we see no sign of it. This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, or may not happen at all."


In the second paper, Matt Penn and William Livingston see a long-term weakening trend in the strength of sunspots, and predict that by Cycle 25 magnetic fields erupting on the Sun will be so weak that few if any sunspots will be formed. Spots are formed when intense magnetic flux tubes erupt from the interior and keep cooled gas from circulating back to the interior. For typical sunspots this magnetism has a strength of 2,500 to 3,500 gauss (Earth's magnetic field is less than 1 gauss at the surface); the field must reach at least 1,500 gauss to form a dark spot.


Using more than 13 years of sunspot data collected at the McMath-Pierce Telescope at Kitt Peak in Arizona, Penn and Livingston observed that the average field strength declined about 50 gauss per year during Cycle 23 and now in Cycle 24. They also observed that spot temperatures have risen exactly as expected for such changes in the magnetic field. If the trend continues, the field strength will drop below the 1,500 gauss threshold and spots will largely disappear as the magnetic field is no longer strong enough to overcome convective forces on the solar surface.


Moving outward, Richard Altrock, manager of the Air Force's coronal research program at NSO's Sunspot, NM, facilities has observed a slowing of the "rush to the poles," the rapid poleward march of magnetic activity observed in the Sun's faint corona. Altrock used four decades of observations with NSO's 40-cm (16-inch) coronagraphic telescope at Sunspot.
"A key thing to understand is that those wonderful, delicate coronal features are actually powerful, robust magnetic structures rooted in the interior of the Sun," Altrock explained. "Changes we see in the corona reflect changes deep inside the Sun."


Altrock used a photometer to map iron heated to 2 million °C (3.6 million °F). Stripped of half of its electrons, it is easily concentrated by magnetism rising from the Sun. In a well-known pattern, new solar activity emerges first at about 70 degrees latitude at the start of a cycle, then towards the equator as the cycle ages. At the same time, the new magnetic fields push remnants of the older cycle as far as 85 degrees poleward.


"In cycles 21 through 23, solar maximum occurred when this rush appeared at an average latitude of 76 degrees," Altrock said. "Cycle 24 started out late and slow and may not be strong enough to create a rush to the poles, indicating we'll see a very weak solar maximum in 2013, if at all. If the rush to the poles fails to complete, this creates a tremendous dilemma for the theorists, as it would mean that Cycle 23's magnetic field will not completely disappear from the polar regions (the rush to the poles accomplishes this feat). No one knows what the Sun will do in that case."


All three of these lines of research to point to the familiar sunspot cycle shutting down for a while.


"If we are right," Hill concluded, "this could be the last solar maximum we'll see for a few decades. That would affect everything from space exploration to Earth's climate."


In response to news inquiries and stories, Dr. Frank Hill issued a follow-up statement:


"We are NOT predicting a mini-ice age. We are predicting the behavior of the solar cycle. In my opinion, it is a huge leap from that to an abrupt global cooling, since the connections between solar activity and climate are still very poorly understood. My understanding is that current calculations suggest only a 0.3 °C decrease from a Maunder-like minimum, too small for an ice age. It is unfortunate that the global warming/cooling studies have become so politically polarizing."


# # # These results have been presented at the current meeting of the AAS/SPD.
Citations:
16.10: "Large-Scale Zonal Flows During the Solar Minimum -- Where Is Cycle 25?" by Frank Hill, R. Howe, R. Komm, J. Christensen-Dalsgaard, T.P. Larson, J. Schou & M. J. Thompson.
17.21: "A Decade of Diminishing Sunspot Vigor" by W. C. Livingston, M. Penn & L. Svalgard.
18.04: "Whither Goes Cycle 24? A View from the Fe XIV Corona" by R. C. Altrock.


http://www2.nso.edu/press/SolarActivityDrop.html