Solar variability affects Earth’s climate in many intricate and nonlinear ways. Most effects are ultimately driven and modulated by the solar magnetic field and its conspicuous solar cycle, which repeats approximately every 11 years, referred to as Maunder* maximums and minimums which even affect low band radio reception by its effects on the Ionosphere.
Careful statistical analysis is required to extract the effect of solar variability on climate from a noisy background.The effect of solar variability on climate is mostly hidden in the natural variability of the climate system; thus, careful statistical analysis is required to extract it from a noisy background. Such analyses require records that extend over a long period of time, but the paucity of observations in existing records poses a serious challenge. For example, scientists have been making direct measurements (from space) of the total solar radiative input into Earth’s atmosphere only since 1978, although there had been earlier attempts to measure it from the ground.
Although solar radiation represents more than 99.9% of the energy entering Earth’s system, radiation is not the only means by which solar variability affects climate. Another source of variability comes from energetic particles, some of which originate from the Sun.
The sun shown in ultraviolet light.
The most energetic particles, known as galactic cosmic rays, have an extragalactic origin; their role in cloud formation has attracted strong media interest. However, recent experiments at the European Organization for Nuclear Research (CERN) suggest that these cosmic rays have a limited impact on the microphysics of clouds. Energetic protons produced during solar flares and energetic electrons that originate from the Earth’s magnetosphere have received much less attention, yet they may play a role by contributing to catalytic ozone loss in the polar atmosphere [Andersson et al., 2014]. Such ozone depletion primarily affects the upper layers of the atmosphere (60–80 kilometers) but eventually it affects the lower layers and climate as well.
For many years, a single quantity, total solar irradiance (TSI), which describes the total solar radiated power incident on Earth’s upper atmosphere, was used to summarize the solar contribution into climate models, neglecting other contributions. The assumption was that solar radiation would mainly act on Earth’s environment by directly heating the oceans, continents, and lower atmosphere.
The discovery of the effects of radiation in the ultraviolet (UV) wavelength band shattered this simple picture. Researchers have shown that UV radiation affects climate through direct heating and the production and destruction of ozone in the stratosphere, which then leads to regional effects at Earth’s surface through a complex chain of mechanisms.
Although the TSI is a key ingredient in Earth’s global energy budget, the spectrally resolved solar irradiance (SSI) provides much deeper insight into the impact of solar variability on the atmosphere. Unlike TSI, which integrates the contribution from all spectral bands (UV, visible, infrared) into one single quantity, SSI reveals variations at specific wavelengths, each of which affects Earth’s environment in a different way.
Making accurate SSI observations is a real challenge: SSI measurements must be carried out from space.Unfortunately, the record of SSI observations is fragmented in time and in wavelength, even more so than TSI observations.
Making accurate SSI (spectrally resolved solar irradiance observations) is a real challenge: SSI measurements must be carried out from space to capture radiation that would otherwise be partly absorbed by Earth’s atmosphere. However, many instruments degrade in the harsh environment of space, leaving researchers with large uncertainties in the interpreted data.
To overcome challenges with solar irradiance models, scientists need to piece together a record longer than the past few decades. An international team of scientists, challenged by the fragmentation of historical solar forcing data, met at ISSI (International Space Science Institute, Bern, Switzerland) to produce another comprehensive data set for direct use by climate modelers, who require long-term reconstructions.
This data set, which runs from 1850 to 2015, includes solar radiative forcing using TSI and SSI reconstructions. It is the first to incorporate contributions from energetic particles such as magnetospheric electrons, solar protons, and galactic cosmic rays. Here, too, we welcome community feedback for improving future versions. The data set comes with recommendations on solar-induced ozone variations that are consistent with these solar forcing data, and it has been recommended for the current Coupled Model Intercomparison Project Phase 6 (
CMIP6) initiative [Matthes et al., 2017].
See:
https://www.nasa.gov/mission_pages/...es-the-Solar-Cycle-Affect-Earths-Climate.html
See:
https://www.weather.gov/fsd/sunspots
See:
https://eos.org/science-updates/better-data-for-modeling-the-suns-influence-on-climate
* The Maunder minimum was the unexplained period of drastically reduced sunspot activity that occurred between 1645 and 1715.
Graph of average yearly sunspot numbers showing the 11-year solar cycle. Encyclopædia Britannica, Inc.
English astronomer
Edward Walter Maunder pointed out that very few sunspots had been observed between 1645 and 1715. Astronomers such as
John Flamsteed and
Gian Domenico Cassini who did observe sunspots during that period noted that they were the first they had seen in years. However, most of Maunder’s fellow astronomers blamed the lack of sunspots on haphazard and sporadic observations of the
Sun by 17th- and 18th-century astronomers. In 1976 American astronomer John Allen Eddy used extensive historical data to show that 17th- and 18th-century astronomers had indeed been careful and diligent observers of the Sun. Eddy also conducted detailed analysis of levels of carbon-14 (a
radioactive isotope whose abundance increases during periods of low solar activity) in tree-rings to confirm that during two distinct historical periods sunspot activity was greatly decreased. Eddy dubbed the
conspicuous solar calm that lasted from 1645 to 1715 the Maunder minimum, after Maunder. (Eddy also examined evidence of an earlier peaceful interval between 1450 and 1540, which he called the Spörer minimum in honour of the 19th-century German scientist Gustav Spörer, another early observer of the irregularities.)
The Maunder minimum coincided with the coldest part of the “Little Ice Age**” (
c. 1500–1850) in the Northern Hemisphere, when the
Thames River in England froze over during winter, Viking settlers abandoned Greenland, and Norwegian farmers demanded that the Danish king (Norway was then ruled by Denmark) recompense them for lands occupied by advancing
glaciers. The physical mechanism that explains how a drastic change in solar activity affects Earth’s
climate is unknown, and a single episode, however suggestive, does not prove that lower sunspot numbers produce cooling. However, if real, the phenomenon may indicate that the Sun can influence the climate on Earth with even slight fluctuations.
See:
https://www.britannica.com/science/Maunder-minimum
** Little Ice Age was a period of regionally cold conditions between roughly AD 1300 and 1850. The term “Little Ice Age” is somewhat questionable, because there was no single, well-defined period of prolonged cold. There were two phases of the Little Ice Age, the first beginning around 1290 and continuing until the late 1400s. There was a slightly warmer period in the 1500s, after which the climate deteriorated substantially, with the coldest period between 1645 and 1715 . During this coldest phase of the Little Ice Age there are indications that average winter temperatures in Europe and North America were as much as 2°C lower than at present.
There is substantial historical evidence for the Little Ice Age. The Baltic Sea froze over, as did many of the rivers and lakes in Europe. Pack ice expanded far south into the Atlantic making shipping to Iceland and Greenland impossible for months on end. Winters were bitterly cold and summers were often cool and wet. These conditions led to widespread crop failure, famine, and population decline. The tree line and snowline dropped and glaciers advanced, overrunning towns and farms in the process. There were increased levels of social unrest as large portions of the population were reduced to starvation and poverty.
During the height of the Little Ice Age , it was in general about one degree Celsius colder than at present. The Baltic Sea froze over, as did most of the rivers in Europe. Winters were bitterly cold and prolonged, reducing the growing season by several weeks. These conditions led to widespread crop failure, famine, and in some regions population decline.
The prices of grain increased and wine became difficult to produce in many areas and commercial vineyards vanished in England. Fishing in northern Europe was also badly affected as cod migrated south to find warmer water. Storminess and flooding increased and in mountainous regions the treeline and snowline dropped. In addition glaciers advanced in the Alps and Northern Europe, overrunning towns and farms in the process.
Iceland was one of the hardest hit areas. Sea ice, which today is far to the north, came down around Iceland. In some years, it was difficult to bring a ship ashore anywhere along the coast. Grain became impossible to grow and even hay crops failed. Volcanic eruptions made life even harder. Iceland lost half of its population during the Little Ice Age.
Rhône glacier ca. 1870. Source: Wikimedia Commons
Tax records in Scandinavia show many farms were destroyed by advancing ice of glaciers and by melt water streams. Travellers in Scotland reported permanent snow cover over the Cairngorm Mountains in Scotland at an altitude of about 1200 metres. In the Alps, the glaciers advanced and threatened to bulldozed towns. Ice-dammed lakes burst periodically, destroying hundreds of buildings and killing many people. As late as 1930 the French Government commissioned a report to investigate the threat of the glaciers. They could not have foreseen that human induced global warming was to deal more effective with this problem than any committee ever could.
Despite the difficulties in marginal regions, culture and economy were generally flowering in Europe during the Little Ice Age. This is most visible in the way that people transformed their environment during the 17th and 18th centuries with expanding agriculture and large scale land reclamation, for example in the Netherlands and England.
Winter landscape by Brueghel the Elder***. Source: Wikimedia Commons
The Little Ice Age also coincided with the maritime expansion of Europe and the creation of seaborne trading and later colonial empires. First came the Spanish and Portuguese, followed by the Dutch, English and other European nations. Key to this success was the development of shipbuilding technology which was a response to both trading, strategic but also climatic pressures.
Art and architecture also flourished, which is probably best embodied in the wonderful winter landscape paintings which can be considered a direct result of the Little Ice Age. These paintings show us ice-skaters enjoying themselves, a sign that they were more than capable to withstand the hasher winter conditions and that they had also enough food (Robinson: 2005). The latter is a key element in the success of European culture at that time.
On balance, the Little Ice Age affected northern European history in different ways. Regions that diversified agriculture and had good access to the international trade network, like Britain and the Low Countries, could cope quite easily with increasingly severe weather conditions. They could import food when harvests failed. Trade also gave them the financial base to develop technological responses.
In isolated regions, like high alpine areas of Switzerland, the Highlands of Scotland or Iceland, the unfavorable condition of the Little Ice Age, especially cold springs and harvest rains as well as longer winters, strongly influenced grain prices and were drivers for local famines. In central Europe the Little Ice Age was characterized by increased droughts as well as by increased flood frequency. Generally, the impact on different parts of Europe differed considerably. Some regions thrived while others struggled.
The earth does not have some magical average natural temperature to which it always returns. If it warms, the earth must be receiving more heat or retaining more heat. If it cools, then it must be receiving less heat from the Sun or radiating more into space, or both. Is that what happened during the Little Ice Age?
The exact cause of the Little Ice Age is unknown, but there is a striking coincidence in the sunspot cycle and the timing of the Little Ice Age. During the Little Ice Age, there is a minimum in sunspots, indicating an inactive and possibly cooler sun. This absence of sunspots is called the Maunder Minimum.
Source: Robert A. Rohde
The Maunder Minimum occurred during the coldest period of the Little Ice Age between 1645 and 1715 AD, when the number of sunspots was very low. It is named after British astronomer E.W. Maunder who discovered the dearth of sunspots during that period. The lack of sunspots meant that solar radiation was probably lower at this time, but models and temperature reconstructions suggest this would have reduced average global temperatures by 0.4ºC at most, which does not explain the regional cooling of the climate in Europe and North America.
What does explain a drop of up to 2 degrees C in winter temperatures? The North Atlantic is one of the most climatically unstable regions in the world. This is caused by a complex interaction between the atmosphere and the ocean. The main feature of this is the North Atlantic Oscillation (NAO), a seesaw of atmospheric pressure between a persistent high over the Azores and an equally persistent low over Iceland. Sometimes the pressure cells weaken and that has severe consequences for the weather in Europe.
Positive North Atlantic Oscillation. Image Courtesy Martin Visbeck
When the Azores high pressure grows stronger than usual and the Icelandic low becomes deeper than normal, this results in warm and wet winters in Europe and in cold and dry winters in northern Canada and Greenland. This also means that the North Atlantic Storm track move north, directing more frequent and severe stroms over northern Europe. This situation is called a Positive NAO Index.
Negative North Atlantic Oscillation. Image Courtesy Martin Visbeck
When both pressure systems are weak, cold air can reach Northern Europe more easily during the winter months resulting in cold winters and the North Atlantic strom track is pushed south, causing wet weather in the Mediterranean. This situation is called a Negative NAO Index.
It is now thought that during the Little Ice Age, the NAO (North Atlantic Oscillation) Index was more persistent in a negative mode. For this reason the regional variability during the Little Ice Age can also be understood in terms of changes in the atmospheric circulation patterns in the North Atlantic region.
See:
https://www.eh-resources.org/little-ice-age/
*** Brueghel the Elder
by Jacob Wisse
Stern College for Women, Yeshiva University
October 2002
Pieter Bruegel I (ca. 1525–1569), commonly known as Pieter Bruegel the Elder, was the greatest member of a large and important southern Netherlandish family of
artists active for four generations in the sixteenth and seventeenth centuries. A longtime resident of Antwerp, the center of publishing in the Netherlands and a vibrant commercial capital, Bruegel brought a humanizing spirit to traditional subjects and boldly created new ones. He was an astoundingly inventive
painter and
draftsman, and, due to the continuity of the family trade and the industry that developed in
prints after his works, Bruegel’s impact was widespread and long lasting.
Born in or near Breda about 1525, Bruegel settled fairly early in Antwerp, where he became a master in the painters’ Guild of Saint Luke between 1551 and 1552. After a
trip to Italy, he began a long-standing association with Hieronymus ****, whose Antwerp publishing house, At the Four Winds, produced prints on a range of subjects, from parables to
landscapes. Between 1555 and 1563, Bruegel made over forty designs for
engravings, capitalizing on the strong market demand for images in the style or manner of Hieronymus Bosch (ca. 1450–1516). Bruegel’s Big Fish Eat Little Fish(Albertina, Vienna) was even attributed to Bosch in ****’s print, though all subsequent engravings were inscribed “Bruegel inventor.” The novel and ingenious way in which Bruegel translated moralizing subjects into vernacular language is most apparent in his original drawings and paintings, such as
Netherlandish Proverbs (Gemäldegalerie, Staatliche Museen, Berlin), which depicts over 100 proverbs in the familiar setting of a Flemish village; it became one of the artist’s most popular images—at least sixteen copies of the painting are known. In religious or
mythological depictions, such as the
Landscape with the Fall of Icarus (Musées Royaux des Beaux-Arts, Brussels), Bruegel expanded the viewers perspective to make the titular action but one part of a startlingly broad vision of the natural and cultivated world.
A number of Bruegel’s paintings focus on the lives of Flemish commoners, which earned him the nickname “peasant Bruegel,” as well as the misguided reputation for being of peasant birth. In
Kermis (Kunsthistorisches Museum, Vienna) and The Dirty Bride(
32.63), for instance, Bruegel depicts the boisterous activities of a country fair and a folk play, respectively, paying particularly close attention to the worn costumes and broad, emphatic gestures of the celebrants. But while these works demonstrate the artist’s attentive eye for detail and attest to his direct observation of village settings, they are far from simple re-creations of everyday life. The powerful compositions, brilliantly organized and controlled, reflect a sophisticated artistic design. Bruegel was, in fact, patronized mainly by scholars, wealthy businessmen, and connoisseurs, and was on friendly terms with some of the most prominent humanists of the Netherlands, including the cartographer Abraham Ortelius and the publisher Christoph Plantin. The ongoing debate over the interpretation of Bruegel’s “peasant” images underscores the complexity and originality of his conception.
Bruegel’s use of landscape also defies easy interpretation, and demonstrates perhaps the artist’s greatest innovation. Working in the aftermath of the
Reformation, Bruegel was able to separate his landscapes from long-standing iconographic tradition, and achieve a contemporary and palpable vision of the natural world. For the Antwerp home of the wealthy merchant Niclaes Jongelinck, who owned no less than sixteen of the artist’s works, Bruegel executed a series of paintings representing the Seasons, of which five survive: Gloomy Day, Return of the Herd,
Hunters in the Snow (all Kunsthistorisches Museum, Vienna), Haymaking (Národní Galerie, Prague), and The Harvesters (
19.164). Though rooted in the legacy of calendar scenes, Bruegel’s emphasis is not on the labors that mark each season but on the atmosphere and transformation of the landscape itself. These panoramic compositions suggest an insightful and universal vision of the world—a vision that distinguishes all the work of their remarkable creator, Pieter Bruegel the Elder.
Citation
Wisse, Jacob. “Pieter Bruegel the Elder (ca. 1525–1569).” In Heilbrunn Timeline of Art History. New York: The Metropolitan Museum of Art, 2000–.
http://www.metmuseum.org/toah/hd/brue/hd_brue.htm (October 2002)
Further Reading
Orenstein, Nadine, ed. Pieter Bruegel the Elder: Drawings and Prints. Exhibition catalogue. New York: Metropolitan Museum of Art, 2001.
See on MetPublications
Stechow, Wolfgang. Pieter Bruegel, the Elder. New York: Abrams, 1970.
We are still missing an international framework that enables a critical comparison of irradiance models with the aim of improving them for better data over time. The highest priority, however, is to continue simultaneous total and spectral irradiance observations by different instruments, on Earth and by satellites. We need to quantify more precisely the critical role of the Sun, our nearest star, in the natural forcing of climate variability and climate change. Jolly old Mr Sun, the hero of so many songs, who provides some 99.9% of the energy reaching us, still has a lot to tell us.
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