Sunday, 12 July 2015

The Sun is Going to Sleep...Are we heading for a Solar Minimum

Thanks to Ben at
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Published on 10 Jul 2015
This Members-Only content from has been shared on YouTube because it describes and frames what is probably the single most significant heliophysics discovery of the year. The subject of a coming grand minimum, despite some of the experts' concurrence and the data suggesting only one near-term outcome for the sun, has drawn controversy from many in the heliophysics community; I have fallen on the side of a coming grand minimum and am not shy about my praise for this mathematical model. I don't like most models; they tend not to match observational data - this one does.

Video Articles:
New Model Says Minimum is Coming:
Solar N/S Divide Article:
Observing the Frontier Conference:


The Maunder Minimum, also known as the "prolonged sunspot minimum", is the name used for the period starting in about 1645 and continuing to about 1715 when sunspots became exceedingly rare, as noted by solar observers of the time. The term was introduced after John A. Eddy published a landmark 1976 paper in Science.[1] Astronomers before Eddy had also named the period after the solar astronomers Annie Maunder (1868-1947) and E. Walter Maunder (1851–1928) who studied how sunspot latitudes changed with time.[2] The period the husband and wife team examined included the second half of the 17th century. Two papers were published in Edward Maunder's name in 1890 and 1894, and he cited earlier papers written by Gustav Spörer.[3] Due to the social climate of the time, Annie's contribution was not publicly recognized.[4] Spörer noted that during one 30-year period within the Maunder Minimum observations showed fewer than 50 sunspots, as opposed to a more typical 40,000–50,000 spots in modern times.[5] Like the Dalton Minimum and Spörer Minimum, the Maunder Minimum coincided with a period of lower-than-average European temperatures.
It caused London's River Thames to freeze over, and 'frost fairs' became popular. This period of solar inactivity also corresponds to a climatic period called the 'Little Ice Age' when rivers that are normally ice-free froze and snow fields remained year-round at lower altitudes. 
There is evidence that the Sun has had similar periods of inactivity in the more distant past, Nasa says.

The Frozen Thames, 1677

The connection between solar activity and terrestrial climate is an area of on-going research. Some scientists hypothesize that the dense wood used in Stradivarius instruments was caused by slow tree growth during the cooler period. 
Instrument maker Antonio Stradivari was born a year before the start of the Maunder Minimum.

Maunder Minimum (also known as the prolonged sunspot minimum) is the name used for the period starting in about 1645 and continuing to about 1715 when sunspots became exceedingly rare, as noted by solar observers of the time

Sunspot observations 

The Maunder Minimum occurred between 1645 and 1715 when very few sunspots were observed. This was not due to a lack of observations; during the 17th century, Giovanni Domenico Cassini carried out a systematic program of solar observations at the Observatoire de Paris, thanks to the astronomers Jean Picard and Philippe de La Hire. Johannes Hevelius also performed observations on his own. The total numbers of sunspots (but not Wolf numbers) in different years were as follows: 

Year                          Sunspots 
1610                               9 
1620                               6 
1630                               9 
1640                               0 
1650                               3 
1660                               Some sunspots reported by Jan Heweliusz in Machina Coelestis 
1670                               0 
1680                               1 huge sunspot observed by Giovanni Domenico Cassini

During the Maunder Minimum enough sunspots were sighted so that 11-year cycles could be extrapolated from the count. The maxima occurred in 1676, 1684, 1695, 1705 and 1716. The sunspot activity was then concentrated in the southern hemisphere of the Sun, except for the last cycle when the sunspots appeared in the northern hemisphere, too. According to Spörer's law, at the start of a cycle, spots appear at ever lower latitudes until they average at about latitude 15° at solar maximum. The average then continues to drift lower to about 7° and after that, while spots of the old cycle fade, new cycle spots start appearing again at high latitudes. The visibility of these spots is also affected by the velocity of the sun's surface rotation at various latitudes: 

Visibility is somewhat affected by observations being done from the ecliptic. The ecliptic is inclined 7° from the plane of the Sun's equator (latitude 0°).

Solar latitude         Rotation period (days) 
0°                                  24.7 
35°                                26.7 
40°                                28.0 
75°                                33.0

Little Ice Age

Comparison of group sunspot numbers (top), Central England Temperature (CET) observations (middle) and reconstructions and modeling of Northern Hemisphere Temperatures (NHT). The CET in red are summer averages (for June, July and August) and in blue winter averages (for December of previous year, January and February). NHT in grey is the distribution from basket of paleoclimate reconstructions (darker grey showing higher probability values) and in red are from model simulations that account for solar and volcanic variations. By way of comparison, on the same scales the anomaly for modern data (after 31 December 1999) for summer CET is +0.65oC, for winter CET is +1.34oC, and for NHT is +1.08oC. Sunspot data are as in supplementary data to and Central England Temperature data are as published by the UK Met Office The NHT data are described in box TS.5, Figure 1 of the IPCC AR5 report of Working Group 1.
The Maunder Minimum coincided with the middle part of the Little Ice Age, during which Europe and North America experienced very cold winters. A causal connection between low sunspot activity and cold European winters has recently been made using the longest existing surface temperature record, the Central England Temperature record and also using the ERA-40 re-analysis dataset.
A potential explanation of this has been offered by observations by NASA's Solar Radiation and Climate Experiment, which suggest that solar UV output is more variable over the course of the solar cycle than scientists had previously thought In 2011, an article was published in the Nature Geoscience journal that uses a climate model with stratospheric layers and the SORCE data to tie low solar activity to jet stream behavior and mild winters in some places (southern Europe and Canada/Greenland) and colder winters in others (northern Europe and the United States). In Europe, examples of very cold winters are 1683-4, 1694-5, and the winter of 1708–9. In such years, River Thames frost fairs were held. However the Thames ceased to freeze in the 19th century largely because the removal of the "Old" (medieval) London Bridge in 1825 dramatically increased the river's flow into the Pool of London. The original 800–900 feet (240–270 m) bridge stood upon 19 irregularly spaced arches that were set into the river bed on large starlings. It acted as a weir holding back the slack upstream waters from the tidal brackish, salt water downstream. The construction of Thames Embankment (began 1862) further increased the river's hydrological flow by narrowing the width of waterway through the centre of capital.
Note that the term "Little Ice Age" applied to the Maunder minimum is something of a misnomer as it implies a period of unremitting cold (and on a global scale), which is not the case. For example, the coldest winter in the Central England Temperature record is 1683-4, but the winter just 2 years later (both in the middle of the Maunder minimum) was the fifth warmest in the whole 350-year CET record. Furthermore, summers during the Maunder minimum were not significantly different to those seen in subsequent years. The drop in global average temperatures in paleoclimate reconstructions at the start of the Little Ice Age was between about 1560 and 1600, whereas the Maunder minimum began almost 50 years later.

Other observations

Solar activity events recorded in radiocarbon.

Graph showing proxies of solar activity, including changes in sunspot number and cosmogenic isotope production.
Some scientists hypothesize that the dense wood used in Stradivarius instruments was caused by slow tree growth during the cooler period. Instrument maker Antonio Stradivari was born a year before the start of the Maunder Minimum.
Past solar activity may be recorded by various proxies including carbon-14 and beryllium-10.
These indicate lower solar activity during the Maunder Minimum. The scale of changes resulting in the production of carbon-14 in one cycle is small (about one percent of medium abundance) and can be taken into account when radiocarbon dating is used to determine the age of archaeological artifacts. The interpretation of the beryllium-10 and carbon-14 cosmogenic isotope abundance records stored in terrestrial reservoirs such as ice sheets and tree rings has been greatly aided by reconstructions of solar and heliospheric magnetic fields based on historic data on Geomagnetic storm activity, which bridge the time gap between the end of the usable cosmogenic isotope data and the start of modern spacecraft data.
Other historical sunspot minima have been detected either directly or by the analysis of the cosmogenic isotopes; these include the Spörer Minimum (1450–1540), and less markedly the Dalton Minimum (1790–1820). In a 2012 study, sunspot minima have been detected by analysis of carbon-14 in lake sediments.In total there seem to have been 18 periods of sunspot minima in the last 8,000 years, and studies indicate that the sun currently spends up to a quarter of its time in these minima.
A paper based on an analysis of a Flamsteed drawing, suggests that the Sun's surface rotation slowed in the deep Maunder minimum (1684).
During the Maunder Minimum aurorae had been observed seemingly normally, with a regular decadal-scale cycle. This is somewhat surprising because the later, and less deep, Dalton sunspot minimum is clearly seen in auroral occurrence frequency, at least at lower geomagnetic latitudes. Because geomagnetic latitude is an important factor in auroral occurrence, (lower-latitude aurorae requiring higher levels of solar-terrestrial activity) it becomes important to allow for population migration and other factors that may have influenced the number of reliable auroral observers at a given magnetic latitude for the earlier dates. Decadal-scale cycles during the Maunder minimum can also be seen in the abundances of the beryllium-10 cosmogenic isotope (which unlike carbon-14 can be studied with annual resolution) but these appear to be in antiphase with any remnant sunspot activity. An explanation in terms of solar cycles in loss of solar magnetic flux was proposed in 2012.
The fundamental papers on the Maunder minimum (Eddy, Legrand, Gleissberg, Schröder, Landsberg et al.) have been published in Case studies on the Spörer, Maunder and Dalton Minima.

The number of sunspots increases and decreases over time in a regular, approximately 11-year cycle, called the sunspot cycle. The exact length of the cycle can vary. It has been as short as eight years and as long as fourteen, but the number of sunspots always increases over time, and then returns to low again.

” Irregular heartbeat of the Sun driven by double dynamo" 
   July 9, 2015 by Dr Robert Massey 

A new model of the Sun’s solar cycle is producing unprecedentedly accurate predictions of irregularities within the Sun’s 11-year heartbeat. The model draws on dynamo effects in two layers of the Sun, one close to the surface and one deep within its convection zone. Predictions from the model suggest that solar activity will fall by 60 per cent during the 2030s to conditions last seen during the ‘mini ice age’ that began in 1645. Results will be presented today by Prof Valentina Zharkova at the National Astronomy Meeting in Llandudno. It is 172 years since a scientist first spotted that the Sun’s activity varies over a cycle lasting around 10 to 12 years. But every cycle is a little different and none of the models of causes to date have fully explained fluctuations. Many solar physicists have put the cause of the solar cycle down to a dynamo caused by convecting fluid deep within the Sun. Now, Zharkova and her colleagues have found that adding a second dynamo, close to the surface, completes the picture with surprising accuracy. “We found magnetic wave components appearing in pairs, originating in two different layers in the Sun’s interior. They both have a frequency of approximately 11 years, although this frequency is slightly different, and they are offset in time. Over the cycle, the waves fluctuate between the northern and southern hemispheres of the Sun. Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97%,” said Zharkova. Zharkova and her colleagues derived their model using a technique called ‘principal component analysis’ of the magnetic field observations from the Wilcox Solar Observatory in California. They examined three solar cycles-worth of magnetic field activity, covering the period from 1976-2008. In addition, they compared their predictions to average sunspot numbers, another strong marker of solar activity. All the predictions and observations were closely matched. Looking ahead to the next solar cycles, the model predicts that the pair of waves become increasingly offset during Cycle 25, which peaks in 2022. During Cycle 26, which covers the decade from 2030-2040, the two waves will become exactly out of synch and this will cause a significant reduction in solar activity.

Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle. Credit: SOHO/ESA/NASA

Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle. Credit: SOHO/ESA/NASA

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Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle. Credit: SOHO/ESA/NASA

Read more at:
Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle. Credit: SOHO/ESA/NASA

Read more at:
Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle. Credit: SOHO/ESA/NASA

Read more at:
 “In cycle 26, the two waves exactly mirror each other – peaking at the same time but in opposite hemispheres of the Sun. Their interaction will be disruptive, or they will nearly cancel each other. We predict that this will lead to the properties of a ‘Maunder minimum’,” said Zharkova. “Effectively, when the waves are approximately in phase, they can show strong interaction, or resonance, and we have strong solar activity. When they are out of phase, we have solar minimums. When there is full phase separation, we have the conditions last seen during the Maunder minimum, 370 years ago.

From  The Carbon Brief

Solar minimum could bring cold winters to Europe and US, but would not hold off climate change

  • 23 Jun 2015, 16:00
  • Robert McSweeney
Low winter sun over a common
 Winter sun | Flickr

Over the past few decades, our Sun has been relatively active, giving off high levels of the solar radiation that warms the Earth. However, in recent years this peak activity has tailed off, prompting scientists to wonder if the Sun is heading into a period of lower output.
A new study says even if the Sun's activity did drop off for a while, it wouldn't have much impact on rising global temperatures. But it could mean a higher chance of a chilly winter in Europe and the US, the researchers say.

Solar output

The Sun's activity rises and falls on an approximately 11-year cycle, but it can experience longer variations from one century to another. Over the past 10,000 years, the Sun has hit around 30 periods of very high or very low activity - called 'grand maxima' and 'grand minima'.
One of these occurred between 1645 and 1715, when the Sun went through a prolonged spell of low solar activity, known as the Maunder Minimum. This didn't have much of an effect on global climate, but it was linked to a number of very cold winters in Europe.
In 2010, scientists predicted an 8% chance that we could return to Maunder Minimum conditions within the next 40 years.
But since that study was published, solar activity has declined further, and this likelihood has increased to 15 or 20%, says new research published today in open-access journal Nature Communications.
In fact, the Sun's output has declined faster than any time in our 9,300-year record, say the researchers. And so they set out to analyse what this could mean for global and regional climate.

Small decrease

The researchers used a climate model to run two scenarios where solar activity declines to a grand minimum. They then compared the results with a control scenario where the Sun continues on its regular cycle.
For all model runs they used the RCP8.5 scenario to account for future climate change - this is the scenario with the highest greenhouse gas emissions of those used by the Intergovernmental Panel on Climate Change ( IPCC). Global emissions are currently tracking just above this scenario.
You can see the modelling results in the maps below. Overall, a grand solar minimum could see global average temperature rise trimmed by around 0.12C for the second half of this century, the researchers say. Larger changes (shown as dark greens and blues) are seen in some parts of  the
northern hemisphere
Ineson Et Al (2015) Fig2
Projected difference in annual average surface temperature for 2050-99 between RCP8.5 emissions scenario and a) Solar scenario 1 and b) Solar scenario 2. Areas of blue and green show regions projected to be cooler because of the solar minimum. Source: Ineson, S. et al. (2015)
This wouldn't make much of a dent in global temperature increases that could well exceed four degrees by the end of the century under RCP8.5, says lead author Sarah Ineson, a climate scientist at the UK Met Office.
These results are in keeping with similar studies, she tells Carbon Brief:
"The expected decrease in global mean surface temperature due to a fall in solar irradiation would be small in comparison to the projected anthropogenic warming."
Under the RCP8.5 scenario, the solar minimum would delay warming for only a couple of years, the paper says. This counters the claim that occasionally appears in some sections of the media that a solar minimum could see the Earth head into an ice age.

Northern hemisphere chill

While the impacts of a solar minimum are small on a global scale, they can be larger for specific regions, the paper finds.
How much of the Sun's radiation hits the Earth can affect the circulation patterns over the Atlantic Ocean, Ineson says. This can make natural fluctuations, such as the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO), more negative, which can affect the winters here in the northern hemisphere, she says:
"A more negative Arctic Oscillation or North Atlantic Oscillation is associated with reduced westerly winds over the North Atlantic sector and a southward shift in the mid-latitude storm track which causes reduced temperatures in the US and northern Europe."
Ineson Et Al (2015) Fig4
You can see in the top map of the figure below that climate change is likely to cause a large decrease in frost days across the northern hemisphere winter. But as the second and third maps show, a solar minimum could add another five days of frost per year in much of Europe and the US. 
Change in average number of frost days. Maps show difference in winter (December-February) frost days between a) RCP8.5 model run (2050-99) and historical period (1971-2000), b) Solar minimum Scenario 1 and RCP8.5, and c) Solar minimum Scenario 2 and RCP8.5. Source: Ineson, S. et al. (2015)
For Europe, specifically, the study finds the solar minimum could knock 0.4-0.8C off a projected winter temperature rise of 6.6C, under RCP8.5 and relative to 1971-2000.
Shifting of the storm track across the Atlantic Ocean would also mean less rainfall coming to northern Europe in winter, the study says, slightly reducing the increases projected under climate change.

Temporary effect

With only small impacts on global climate, the study shows that a drop in the Sun's strength shouldn't delay action on climate change, says Prof Joanna Haigh, co-director of the Grantham Institute for Climate Change at Imperial College London, who wasn't involved in the study. She tells Carbon Brief:
"No one should consider the results to provide justification for bothering less about carbon dioxide emissions."
And any impact of a solar minimum on climate would be short-lived, says Haigh, until such time that the Sun's activity increased again.
Prof Jerry Meehl, from the National Centre for Atmospheric Science (NCAR) in Boulder, Colorado, who also wasn't involved, agrees. He tells Carbon Brief that his recent study shows the rebound effect on temperatures is important:
"When the grand solar minimum ends, the climate system warms back up to the levels it would have been if there had never been a grand solar minimum. Thus the effects would be temporary."
So it seems that a dip in the Sun's activity would only have a limited impact on global climate, and wouldn't call a halt to human-caused climate change.
Ineson, S. et al. (2015) Regional climate impacts of a possible future grand solar minimum. Nature Communications, doi:10.1038/ncomms8535