400 year history of sunspot numbers.

Last 30 years of solar variability.

Solar variations are fluctuations in the amount of energy emitted by the Sun. Small variations have been measured from satellites during recent decades. Of interest to climate scientists is whether these variations have a significant effect on the temperature of Earth's atmosphere. Image File history File links Download high-resolution version (1000x425, 41 KB) Description Changes in carbon-14 concentration in the Earths atmosphere, which serves as a long term proxy of solar activity. ... Image File history File links Download high-resolution version (1000x425, 41 KB) Description Changes in carbon-14 concentration in the Earths atmosphere, which serves as a long term proxy of solar activity. ... The Wolf number (also known as the International sunspot number, relative sunspot number, or Zürich number) is a quantity which measures the number of sunspots and groups of sunspots present on the surface of the sun. ... Image File history File links Pic of 20 years of solar output data. ... Image File history File links Pic of 20 years of solar output data. ... The Sun is the star of our solar system. ...

The amount of solar radiation received at the outer surface of Earth's atmosphere was once assumed to not change much (see solar constant) from an average value of 1366 W/m².^[1] The variations in total solar output are so slight (as a percentage of total output) that they remained at or below the threshold of detectability until the satellite era, although the small fraction in ultra-violet wavelengths varies by a few percent. Total solar output is now measured to vary (over the last two 11-year sunspot cycles) by approximately 0.1%^[2][3] or about 1.3 W/m² peak-to-trough of the 11 year sunspot cycle. There are no direct measurements of the longer-term variation and interpretations of proxy measures of variations differ; recent results suggest about 0.1% variation over the last 2000 years [1]. Solar variation has probably been the cause of some climate change, for example during the Maunder minimum. A 2006 study and review of existing literature, published in Nature, determined that there has been no net increase in brightness since the mid 1970s, and that changes in solar output within the past 400 years are unlikely to have played a major part in global warming.[2] Solar irradiance spectrum at top of atmosphere. ... Solar irradiance spectrum at top of atmosphere. ... In climate research, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400,000 years Climate change refers to the variation in the Earths global climate or in regional climates over time. ... The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ...

History of study of solar variations

The longest recorded aspect of solar variations are changes in sunspots. The first record of sunspots dates to around 800 BC in China and the oldest surviving drawing of a sunspot dates to 1128. In 1610, astronomers began using the telescope to make observations of sunspots and their motions. Initial study was focused on their nature and behavior.^[4] Although the physical aspects of sunspots were not identified until the 1900s, observations continued. Study was hampered during the 1600s and 1700s due to the low number of sunspots during what is now recognized as an extended period of low solar activity, this event named the Maunder Minimum. By the 1800s records of their numbers began to show variations in their numbers. A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings and intense magnetic activity, which inhibits convection, forming areas of low surface temperature. ... A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ... 50 cm refracting telescope at Nice Observatory. ... The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ...

Around 1900 connections between solar variations and weather on Earth began to be explored. Challenges are shown in the efforts of Charles Greeley Abbot, assigned by the Smithsonian Astrophysical Observatory (SAO) to detect changes in the radiation of the Sun. His team had to begin by inventing instruments to measure solar radiation. Later, when he was head of the SAO, it established a solar station at Calama, Chile to complement its data from Mount Wilson Observatory. He detected 27 harmonic periods within the 273-month Hale cycles, including 7, 13, and 39 month patterns. He looked for connections to weather by means such as matching opposing solar trends during a month to opposing temperature and precipitation trends in cities. Charles Greeley Abbot (May 31, 1872 – December 17, 1973) was an American astrophysicist, astronomer and Secretary of the Smithsonian Institution. ... The Smithsonian Astrophysical Observatory (SAO) is a research institute of the Smithsonian Institution headquartered in Cambridge, Massachusetts, where it is joined with the Harvard College Observatory (HCO) to form the Harvard-Smithsonian Center for Astrophysics (CfA). ... Calama is a city in the Atacama Desert in northern Chile. ... The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California. ...

Statistical studies of solar activity with weather and climate were particularly popular until the 1980s, when publications blossomed with studies of weather fronts and global meteorological patterns. Photos from space and weather satellites emphasized the importance of clouds and weather fronts. Climate studies and weather forecasting have been enhanced by increasing use of climate models, beginning with simple computer simulations and replacing "solar constant" values with more detailed solar variation as computing power increased and understanding of weather processes improves. Weather is a term that encompasses phenomena in the atmosphere of a planet. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ... GOES-8, a United States weather satellite. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400,000 years Climate change refers to the variation in the Earths global climate or in regional climates over time. ... Modern weather predictions aid in timely evacuations and potentially save lives and property damage Weather map of Europe, 10 December 1887 Weather forecasting is the application of current technology and science to predict the state of the atmosphere for a future time and a given location. ... Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ... A computer simulation or a computer model is a computer program that attempts to simulate an abstract model of a particular system. ... Solar irradiance spectrum at top of atmosphere. ...

Solar activity

Sunspots

Graph showing proxies of solar activity, including changes in sunspot number and cosmogenic isotope production.

Sunspots are relatively dark areas on the surface of the Sun and are thus cooler than its average surface. The number of sunspots correlates with the intensity of solar radiation. The variation is small (of the order of 1 W/m² or 0.1% of the total) and was only established once satellite measurements of solar variation became available in the 1980s. Based on work by Abbot, Foukal et al. (1977) realised that higher values of radiation are associated with more sunspots. Nimbus 7 (launched October 25, 1978) and the Solar Maximum Mission (launched February 14, 1980) detected that because the areas surrounding sunspots are brighter, the overall effect is that more sunspots means a brighter sun. Description This figure shows two different proxies of solar activity during the last several hundred years. ... Description This figure shows two different proxies of solar activity during the last several hundred years. ... A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings and intense magnetic activity, which inhibits convection, forming areas of low surface temperature. ... The Solar Maximum Mission satellite (or SolarMax) was designed to investigate solar phenomenon, particularly solar flares. ...

There had been some suggestion that variations in the solar diameter might cause variations in output. But recent work, mostly from the Michelson Doppler Imager instrument on SOHO, shows these changes to be small, about 0.001% (Dziembowski et al., 2001). Soho is an area of central Londons West End, in the borough of the City of Westminster. ...

Various studies have been made using sunspot number (for which records extend over hundreds of years) as a proxy for solar output (for which good records only extend for a few decades). Also, ground instruments have been calibrated by comparison with high-altitude and orbital instruments. Researchers have combined present readings and factors to adjust historical data. Other proxy data - such as the abundance of cosmogenic isotopes - have been used to infer solar magnetic activity and thus likely brightness. Proxy may refer to something which acts on behalf of something else as in: Proxy democracy, a bottom-up democracy or delegative democracy Proxy server, a computer network service that allows clients to make indirect network connections to other network services Proxy pattern, a software design pattern in computer programming... Cosmogenic refers to rare radioactive isotopes created when cosmic radiation interacts with an atomic nucleus. ...

Sunspot activity has been measured using the Wolf number for about 300 years. This index (also known as the Zürich number) uses both the number of sunspots and the number of groups to compensate for variations in measurement. The Wolf number (also known as the International sunspot number, relative sunspot number, or Zürich number) is a quantity which measures the number of sunspots and groups of sunspots present on the surface of the sun. ...

Reconstruction of solar activity over 11,400 years. Period of equally high activity over 8,000 years ago marked. Present period is on left. Values since 1900 not shown.

Sunspot numbers over the past 11,400 years have been reconstructed using dendrochronologically dated radiocarbon concentrations. The level of solar activity during the past 70 years is exceptional - the last period of similar magnitude occurred over 8,000 years ago. The Sun was at a similarly high level of magnetic activity for only ~10% of the past 11,400 years, and almost all of the earlier high-activity periods were shorter than the present episode.^[5] Image File history File links 11,400 year sunspot reconstruction. ... Image File history File links 11,400 year sunspot reconstruction. ... The growth rings of an unknown tree species, at Bristol Zoo, England Pinus taeda Cross section showing annual rings, Cheraw, South Carolina Pine stump showing growth rings Dendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree-ring growth patterns. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ...

The Medieval Warm Period (MWP) or Medieval Climate Optimum was a time of unusually warm climate in Europe, lasting from about the 10th century to about the 14th century. ... The Medieval Warm Period (MWP) or Medieval Climate Optimum was a time of unusually warm climate in Europe, lasting from about the 10th century to about the 14th century. ... The Spörer Minimum was a period of low solar activity which lasted from about 1420 to 1570 (some say 1450 to 1550). ... The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ... The Dalton Minimum was a period of low solar activity, lasting from about 1790 to 1820. ... History of sunspot number observations showing the recent elevated activity. ...

Solar cycles

Solar cycles are cyclic changes in behavior of the Sun. Many possible patterns have been suggested; only the 11 and 22 year cycles are clear in the observations. It has been suggested that this article or section be merged with Schwabe-Wolf cycle. ...

• 11 years: Most obvious is a gradual increase and decrease of the number of sunspots over a period of about 11 years, called the Schwabe cycle. The Babcock Model explains this as being due to a shedding of entangled magnetic fields. The Sun's surface is also the most active when there are more sunspots, although the luminosity does not change much due to an increase in bright spots (faculae).
• 22 years: Hale cycle. The magnetic field of the Sun reverses during each Schwabe cycle, so the magnetic poles return to the same state after two reversals.
• 87 years: Gleissberg cycle (70-100 years) is thought to be an amplitude modulation of the 11-year Schwabe Cycle (Sonnett and Finney, 1990).Braun, et al, (2005)
• 210 years: Suess cycle. Braun, et al, (2005)
• 2,300 years: Hallstatt cycle
• Other patterns have been detected:
  • In carbon-14: 105, 131, 232, 385, 504, 805, 2,241 years (Damon and Sonnett, 1991).
  • During the Upper Permian 240 million years ago, mineral layers created in the Castile Formation show cycles of 2,500 years.

The sensitivity of climate to cyclical variations in solar forcing will be higher for longer cycles due to the thermal inertia of the ocean, which acts to damp high frequencies. Scafetta and West (2005) found that the climate was 1.5 times as sensitive to 22 year cyclical forcing relative to 11 year cyclical forcing, and that the thermal inertial induced a lag of approximately 2.2 years in cyclic climate response in the temperature data. Samuel Heinrich Schwabe (October 25, 1789–April 11, 1875) was a German astronomer. ... The Babcock Model describes a mechanism which can explain magnetic and sunspot patterns observed on the Sun. ... To meet Wikipedias quality standards, this article may require cleanup. ... Luminosity has different meanings in several different fields of science. ... Planetary nomenclature, like terrestrial nomenclature, is used to uniquely identify a feature on the surface of a planet or natural satellite so that the feature can be easily located, described, and discussed. ... George Ellery Hale, Sc. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... The Permian is a geologic period that extends from about 299. ...

References:

N. Scafetta, B.J. West, "Estimated solar contribution to the global surface warming using the ACRIM TSI satellite composite" GEOPHYSICAL RESEARCH LETTERS, VOL.32, L18713, doi:10.1029/2005GL023849, 2005

Predictions based on patterns

• A simple model based on emulating harmonics by multiplying the basic 11-year cycle by powers of 2 produced results similar to Holocene behavior. Extrapolation suggests a gradual cooling during the next few centuries with intermittent minor warmups and a return to near Little Ice Age conditions within the next 500 years. This cool period then may be followed approximately 1,500 years from now by a return to altithermal conditions similar to the previous Holocene Maximum.^[6]
• There is weak evidence for a quasi-periodic variation in the sunspot cycle amplitudes with a period of about 90 years. These characteristics indicate that the next solar cycle should have a maximum smoothed sunspot number of about 145±30 in 2010 while the following cycle should have a maximum of about 70±30 in 2023.^[7]
• Because carbon-14 cycles are quasi periodic, Damon and Sonett (1989) predict future climate:^[8]

The Holocene epoch is a geological period that extends from the present day back to about 10,000 radiocarbon years, approximately 11,430 ± 130 calendar years BP (between 9560 and 9300 BC). ... The Little Ice Age (LIA) was a period of cooling occurring after a warmer era known as the Medieval climate optimum. ...

Solar irradiance of Earth and its surface

Solar irradiance, or insolation, is the amount of sunlight which reaches the Earth. The equipment used might measure optical brightness, total radiation, or radiation in various frequencies. Historical estimates use various measurements and proxies. TOA and surface insolation, annual mean Insolation is the incoming solar radiation that reaches a planet and its atmosphere or, by extension, any object exposed to solar rays, such as watts per square meter of Sun-facing cross section, across the entire electromagnetic spectrum; most of that power is in...

Solar irradiance spectrum above atmosphere and at surface

There are two common meanings: Solar irradiance spectrum. ... Solar irradiance spectrum. ...

• the radiation reaching the upper atmosphere
• the radiation reaching some point within the atmosphere, including the surface.

Various gases within the atmosphere absorb some solar radiation at different wavelengths, and clouds and dust also affect it. Hence measurements above the atmosphere are needed to observe variations in solar output, within the confounding effects of changes to the atmosphere. Indeed, there is some evidence that sunshine at the Earth's surface has been decreasing in the last 50 years (see global dimming) possibly caused by increased atmospheric pollution, whilst over roughly the same timespan solar output has been nearly constant. NASA photograph showing aircraft contrails and natural clouds. ...

Milankovitch cycle variations

Some variations in insolation are not due to solar changes but rather due to the Earth moving closer or further from the Sun, or changes in the relative amount of radiation reaching regions of the Earth. These have caused variations of as much as 25% (locally; global average changes are much smaller) in solar insolation over long periods. The most recent significant event was an axial tilt of 24° during boreal summer at near the time of the Holocene climatic optimum. Image File history File links Milankovitch_Variations. ... The Holocene Climate Optimum was a warm period during roughly the interval 7,000 to 5,000 years B.P.. This event has also been known by many other names, including: Hypisthermal, Altithermal, Climatic Optimum, Holocene Optimum, Holocene Thermal Maximum, and Holocene Megathermal. ...

For details see the main article: Milankovitch cycles. It has been suggested that Orbital forcing be merged into this article or section. ...

Solar interactions with Earth

There are several ways that solar variations may affect Earth. Some variations, such as changes in the size of the Sun, are presently only of interest in the field of astronomy. A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ...

Changes in total irradiance

• Overall brightness may change.
• The variation during recent cycles has been about 0.1%.
• Changes corresponding to solar changes with periods of 9-13, 18-25, and >100 years been measured in sea-surface temperatures.
• Since the Maunder Minimum, over the past 300 years there probably has been an increase of 0.1 to 0.6%, with climate models often using a 0.25% increase.
• One reconstruction from the ACRIM data show a 0.05% per decade trend of increased solar output between solar minima over the short span of the data set. These display a high degree of correlation with solar magnetic activity as measured by Greenwich Sunspot Number. Wilson, Mordvinov (2003)

Changes in ultraviolet irradiance

• Ultraviolet irradiance (EUV) ranges widely through factors of 2 to 10 during a solar cycle.
• Energy changes in the UV wavelengths involved in production and loss of ozone have atmospheric effects.
  • The 30 hPa pressure level has changed height in phase with solar activity during the last 4 solar cycles.
  • UV irradiance increase causes higher ozone production, leading to stratospheric heating and to poleward displacements in the stratospheric and tropospheric wind systems.
• A proxy study estimates that UV increased by 3% since the Maunder Minimum.

For other uses, see Ozone (disambiguation). ... HPA means Physiology Hypothalamic-Pituitary-Adrenal axis: The hypothalamus, pituitary and adrenal glands work together to regulate hormone levels and maintain homeostasis. ...

Changes in the solar wind and the Sun's magnetic flux

• A more active solar wind and stronger magnetic field reduces the cosmic rays striking the Earth's atmosphere.
• Variations in the solar wind affect the size and intensity of the heliosphere, the volume larger than the Solar System filled with solar wind particles.
• Levels of ¹⁴C and ¹⁰Be show changes tied to solar activity.
• Cosmic ray ionization in the upper atmosphere does change, but significant effects are not obvious.
• As the solar coronal-source magnetic flux doubled during the past century, the cosmic-ray flux has decreased by about 15%.
• The Sun's total magnetic flux rose by a factor of 1.41 from 1964-1996 and by a factor of 2.3 since 1901.

The heliosphere is a bubble in space produced by the solar wind. ...

Effects on clouds

• Cosmic rays may affect formation of clouds.
• 1983-1994 data from the International Satellite Cloud Climatology Project (ISCCP) showed that global low cloud formation was highly correlated with cosmic ray flux.
• The Earth's albedo decreased by about 2.5% over 5 years during the recent solar cycle, as measured by lunar "Earthshine". Similar reduction was measured by satellites during the previous cycle.
• Mediterranean core study of plankton detected a solar-related 11 year cycle, and an increase 3.7 times larger between 1760 and 1950. A considerable reduction in cloud cover is proposed.

Other effects due to solar variation

Interaction of solar particles, the solar magnetic field, and the Earth's magnetic field, cause variations in the particle and electromagnetic fields at the surface of the planet. Extreme solar events can affect electrical devices. Weakening of the Sun's magnetic field is believed to increase the number of interstellar cosmic rays which reach Earth's atmosphere, altering the types of particles reaching the surface. It has been speculated that a change in cosmic rays could cause an increase in certain types of clouds, affecting Earth's albedo. Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Albedo is a ratio of scattered to incident electromagnetic radiation power. ...

Geomagnetic effects

Solar particles interact with Earth's magnetosphere

The Earth's polar aurora are visual displays created by interactions between the solar wind, the solar magnetosphere, the Earth's magnetic field, and the Earth's atmosphere. Variations in any of these affect aurora displays. Image File history File links Download high resolution version (1200x656, 391 KB)Artists rendition of Earths magnetosphere. ... Image File history File links Download high resolution version (1200x656, 391 KB)Artists rendition of Earths magnetosphere. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. ...

Sudden changes can cause the intense disturbances in the Earth's magnetic fields which are called geomagnetic storms. A geomagnetic storm is a temporary disturbance of the Earths magnetosphere. ...

Solar proton events

Energetic protons can reach Earth within 30 minutes of a major flare's peak. During such a solar proton event, Earth is showered in energetic solar particles (primarily protons) released from the flare site. Some of these particles spiral down Earth's magnetic field lines, penetrating the upper layers of our atmosphere where they produce additional ionization and may produce a significant increase in the radiation environment. Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... A Solar Proton Event occurs when high-energy protons, ejected from the suns surface during a solar flare, get caught by the Earths magnetic field and cause ionization in the ionosphere. ...

Galactic cosmic rays

Solar wind and magnetic field create heliosphere around solar system.

An increase in solar activity (more sunspots) is accompanied by an increase in the "solar wind," which is an outflow of ionized particles, mostly protons and electrons, from the sun. The Earth's geomagnetic field, the solar wind, and solar magnetic field deflects galactic cosmic rays (GCR). A decrease in solar activity increases the GCR penetration of the troposphere and stratosphere. GCR particles are the primary source of ionization in the troposphere above 1 km (below 1 km, radon is a dominant source of ionization in many areas). Image File history File links Heliosphere_drawing. ... Image File history File links Heliosphere_drawing. ... The heliosphere is a bubble in space produced by the solar wind. ... The plasma in the solar wind meeting the heliopause For the British comic, see Solar Wind (comic). ... Galactic cosmic rays (GCRs) are the high-energy particles that flow into our solar system from far away in the Galaxy. ... General Name, Symbol, Number radon, Rn, 86 Chemical series noble gases Group, Period, Block 18, 6, p Appearance colorless Atomic mass (222) g/mol Electron configuration [Xe] 4f14 5d10 6s2 6p6 Electrons per shell 2, 8, 18, 32, 18, 8 Physical properties Phase gas Density (0 °C, 101. ...

Levels of GCRs have been indirectly recorded by their influence on the production of carbon-14 and beryllium-10. The Hallstatt solar cycle length of approximately 2300 years is reflected by climatic Dansgaard-Oeschger events. The 80-90 year solar Gleissberg cycles appear to vary in length depending upon the lengths of the concurrent 11 year solar cycles, and there also appear to be similar climate patterns occurring on this time scale. Dansgaard-Oeschger events are rapid climate fluctuations during and at the end of the last ice age. ...

Cloud effects

Changes in ionization affect the abundance of aerosols that serve as the nuclei of condensation for cloud formation. As a result, ionization levels potentially affect levels of condensation, low clouds, relative humidity, and albedo due to clouds. Clouds formed from greater amounts of condensation nuclei are brighter, longer lived, and likely to produce less precipitation. Changes of 3-4% in cloudiness and concurrent changes in cloud top temperatures have been correlated to the 11 and 22 year solar (sunspot) cycles, with increased GCR levels during "antiparallel" cycles.^[9] Global average cloud cover change has been found to be 1.5-2%. Several studies of GCR and cloud cover variations have found positive correlation at latitudes greater than 50° and negative correlation at lower latitudes.^[10] However, not all scientists accept this correlation as statistically significant, and some that do attribute it to other solar variability (e.g. UV or total irradiance variations) rather than directly to GCR changes.^[11][12] Difficulties in such correlations include that many aspects of solar variability change at similar times, and some climate systems have delayed responses. Albedo is a ratio of scattered to incident electromagnetic radiation power. ...

Carbon-14 production

Carbon-14 production showing 12,000 years of geomagnetic and solar effects.

2,300 year Hallstatt solar variation cycles.

Sunspot record (blue) with ¹⁴C (inverted). There is approximately a 60 year delay between sunspot levels and radiocarbon changes.

Solar activity events recorded in radiocarbon.

The production of radiocarbon (Carbon-14: ¹⁴C) also is related to solar activity. Radiocarbon is produced in the upper atmosphere by cosmic ray bombardment of atmospheric nitrogen (¹⁴N) with neutrons, which may have come from the atmosphere. Increased solar activity reduces cosmic rays and reduces ¹⁴C production. Therefore, the ¹⁴C concentration of the atmosphere is lower during sunspot maxima and higher during sunspot minima. By measuring the captured ¹⁴C in wood and counting tree rings, production of radiocarbon relative to recent wood can be measured and dated. A reconstruction of the past 10,000 years shows that the ¹⁴C production was much higher during the mid-Holocene 7,000 years ago and decreased until 1,000 years ago. In addition to variations in solar activity, the long term trends in Carbon-14 production are influenced by changes in the Earth's geomagnetic field and by changes in carbon cycling within the biosphere (particularly those associated with changes in the extent of vegetation since the last ice age).^[13] Image File history File links Download high resolution version (1250x875, 81 KB) Description Historical data for delta 14C over the last 12,000 years (present is represented by 1955 in this chart as 14C calibration is not agreed upon for dates later than 1955). ... Image File history File links Download high resolution version (1250x875, 81 KB) Description Historical data for delta 14C over the last 12,000 years (present is represented by 1955 in this chart as 14C calibration is not agreed upon for dates later than 1955). ... Image File history File links Download high resolution version (1024x384, 54 KB)Red curve shows 2,000-year solar Hallstadzeit Cycles. ... Image File history File links Download high resolution version (1024x384, 54 KB)Red curve shows 2,000-year solar Hallstadzeit Cycles. ... Image File history File links Carbon14-sunspot. ... Image File history File links Carbon14-sunspot. ... Image File history File links Carbon14_with_activity_labels. ... Image File history File links Carbon14_with_activity_labels. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... The Holocene epoch is a geological period that extends from the present day back to about 10,000 radiocarbon years, approximately 11,430 ± 130 calendar years BP (between 9560 and 9300 BC). ... The cause of Earths magnetic field (the surface magnetic field) is not known for certain, but is possibly explained by dynamo theory. ... The Global Biosphere:a false-color composite of CZCS images of plankton concentrations with land vegetation data collected by the Advanced Very High Resolution Radiometer instrument. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...

Global warming

Researchers have correlated solar variation with changes in the Earth's average temperature and climate - sometimes finding an effect, and sometimes not. The IPCC TAR view is that forcing from solar variations is considerably smaller than forcing from greenhouse gases. Measured as a difference from 1750, GHG forcing is estimated as 1.4 W/m2 compared to 0.3 W/m2 from solar.^[14] For a discussion of attribution of causes of current global warming see: Attribution of recent climate change. Some researchers have found a greater effect; Willie Soon and Sallie Baliunas or Douglass and Clader, Geophysical Research Letters, 2002 are typical of these strands. Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ... IPCC is science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the risk of human-induced climate change. The Panel is open to all... The IPCC Third Assessment Report is a product of the Intergovernmental Panel on Climate Change, which is based in Geneva Switzerland, and was established in 1988 by two United Nations organisations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP). ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... Global mean surface temperatures 1856 to 2005 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is the observed increase in the average temperature of the Earths atmosphere and oceans in recent decades. ... Attribution of recent climate change is the problem of discovering what mechanisms are responsible for observed changes in climate. ... Willie Soon (Wei-Hock Soon) is an astrophysicist at the Solar and Stellar Physics Division of the Harvard-Smithsonian Center for Astrophysics. ... Sallie Baliunas is at the Harvard-Smithsonian Center for Astrophysics in the Solar, Stellar, and Planetary Sciences Division and formerly Deputy Director of the Mount Wilson Institute. ...

When effects are found they have tended to be greater than can be explained by direct response to the change in radiative forcing from solar change, so feedback or amplification mechanisms are required.^[15]

The IPCC questions the magnitude of long-term (last hundred or more years) solar variation in section 6.11 of the TAR^[14] and show various results including Lean et al. (1995).^[16] However the Lean 1995 value may well be too high: more recently Lean et al (GRL 2002,^[17]) say: IPCC is science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the risk of human-induced climate change. The Panel is open to all... The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) was issued in 2001. ...

Our simulation suggests that secular changes in terrestrial proxies of solar activity (such as the 14C and 10Be cosmogenic isotopes and the aa geomagnetic index) can occur in the absence of long-term (i.e., secular) solar irradiance changes. ...this suggests that total solar irradiance may also lack significant secular trends. ...Solar radiative forcing of climate is reduced by a factor of 5 when the background component is omitted from historical reconstructions of total solar irradiance ...This suggest that general circulation model (GCM) simulations of twentieth century warming may overestimate the role of solar irradiance variability. ...There is, however, growing empirical evidence for the Sun's role in climate change on multiple time scales including the 11-year cycle ...Climate response to solar variability may involve amplification of climate modes which the GCMs do not typically include. ...In this way, long-term climate change may appear to track the amplitude of the solar activity cycles because the stochastic response increases with the cycle amplitude, not because there is an actual secular irradiance change.

More recently, a study and review of existing literature published in Nature in Sept. 2006 suggests that the evidence is solidly on the side of solar brightness having relatively little effect on global climate, and downplays the likelyhood of significant shifts in solar output over long periods of time. [3]

Solar variation in climate models

Solar forcing 1850-2050 used in a NASA GISS climate model. Recent variation pattern used after 2000.

Climate models are computer simulations which are used to examine understanding of climate behavior. Some models use constant values for solar irradiance, while some include the heating effects of a variable Sun. A good simulation by GCMs of global mean temperature over the last 100 years requires both natural (solar; volcanic) and human (greenhouse gas) factors. Image File history File links Solar forcing used in NASA GISS SI2000 simulations. ... Image File history File links Solar forcing used in NASA GISS SI2000 simulations. ... Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ...

In 2003, Stott et al found that "current climate models underestimate the observed climate response to solar forcing over the twentieth century as a whole, indicating that the climate system has a greater sensitivity to solar forcing than do models." and concluded that "The best estimate of the warming from solar forcing is estimated to be 16% or 36% of greenhouse warming depending on the solar reconstruction."^[18]

Solar variation theory

Solar variation theory is one attempt to account for global warming. Various hypotheses have been proposed to link terrestrial temperature variations to solar variations. The meteorological community has responded with skepticism, in part because theories of this nature have come and gone over the course of the 20th century.^[3] To reconcile theories of an increase in solar radiation with the measurements would require other changes either in the spectrum of the sun (which has not been observed) or in the absorption profile of the atmosphere, which would probably imply some kind of climate change. Global mean surface temperatures 1856 to 2005 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is the observed increase in the average temperature of the Earths atmosphere and oceans in recent decades. ... A hypothesis (from Greek ) is a suggested explanation of a phenomenon or reasoned proposal suggesting a possible correlation between multiple phenomena. ...

Sami Solanki, the director of the Max Planck Institute for Solar System Research in Göttingen, Germany said: Max Planck Institute for Solarsystem Research April 2006 The Max Planck Institute for Solar System Research (MPS) is part of the Max Planck Society which operates 80 research facilities in Germany. ... Göttingen ( ) is a city in Lower Saxony, Germany. ...

The sun has been at its strongest over the past 60 years and may now be affecting global temperatures... the brighter sun and higher levels of so-called "greenhouse gases" both contributed to the change in the Earth's temperature, but it was impossible to say which had the greater impact.^[19]

Over the last twenty years, however, Solanki agrees with the nearly unanimous scientific consensus that the marked upswing in temperatures is indeed to be attributed to human activity.

"Just how large this role [of solar variation] is, must still be investigated, since, according to our latest knowledge on the variations of the solar magnetic field, the significant increase in the Earth’s temperature since 1980 is indeed to be ascribed to the greenhouse effect caused by carbon dioxide." ^[20]

Willie Soon and Sallie Baliunas of the Harvard Observatory correlated historical sunspot counts with temperature proxies. They report that when there are fewer sunspots, the earth cooled (see Maunder Minimum, Little Ice Age) — and that when there are more sunspots the earth warmed (see Medieval Warm Period, though since sunspot numbers were only counted from 1700 the link to the MWP warmth is speculative). Willie Soon (Wei-Hock Soon) is an astrophysicist at the Solar and Stellar Physics Division of the Harvard-Smithsonian Center for Astrophysics. ... Sallie Baliunas is at the Harvard-Smithsonian Center for Astrophysics in the Solar, Stellar, and Planetary Sciences Division and formerly Deputy Director of the Mount Wilson Institute. ... The Harvard College Observatory (or HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Department of Astronomy of Harvard. ... A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings and intense magnetic activity, which inhibits convection, forming areas of low surface temperature. ... In climate research, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained. ... The Maunder minimum in a 400 year history of sunspot numbers The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. ... The Little Ice Age (LIA) was a period of cooling occurring after a warmer era known as the Medieval climate optimum. ... The Medieval Warm Period (MWP) or Medieval Climate Optimum was a time of unusually warm climate in Europe, lasting from about the 10th century to about the 14th century. ...

The theories have usually represented one of three types:

• Solar irradiance changes directly affecting the climate. This is generally considered unlikely, as the variations seem to be too small.
• Variations in the ultraviolet component having an effect. The UV component varies by more than the total.
• Effects mediated by changes in cosmic rays (which are affected by the solar wind, which is affected by the solar output) such as changes in cloud cover.

Although correlations often can be found, the mechanism behind these correlations is a matter of speculation. Many of these speculative accounts have fared badly over time, and in a paper "Solar activity and terrestrial climate: an analysis of some purported correlations" (J. Atmos. and Solar-Terr. Phy., 2003 p801–812) Peter Laut demonstrates problems with some of the most popular, notably those by Svensmark and by Lassen (below). Damon and Laut report in Eos^[21] that the apparent strong correlations displayed on these graphs have been obtained by incorrect handling of the physical data. The graphs are still widely referred to in the literature, and their misleading character has not yet been generally recognized.

In 1991, Knud Lassen of the Danish Meteorological Institute in Copenhagen and his colleague Eigil Friis-Christensen found a strong correlation between the length of the solar cycle and temperature changes throughout the northern hemisphere. Initially, they used sunspot and temperature measurements from 1861 to 1989, but later found that climate records dating back four centuries supported their findings. This relationship appeared to account for nearly 80 per cent of the measured temperature changes over this period (see graph.^[22] Damon and Laut, however, show that when the graphs are corrected for filtering errors, the sensational agreement with the recent global warming, which drew worldwide attention, has totally disappeared. Nevertheless, the authors and other researchers keep presenting the old misleading graph.^[21] Note that the prior link to "graph" is one such example of this.

Sallie Baliunas, an astronomer at the Harvard-Smithsonian Center for Astrophysics, has been among the supporters of the theory that changes in the sun "can account for major climate changes on Earth for the past 300 years, including part of the recent surge of global warming."^[23] Sallie Baliunas is at the Harvard-Smithsonian Center for Astrophysics in the Solar, Stellar, and Planetary Sciences Division and formerly Deputy Director of the Mount Wilson Institute. ...

On May 6, 2000, however, New Scientist magazine reported that Lassen and astrophysicist Peter Thejll had updated Lassen's 1991 research and found that while the solar cycle still accounts for about half the temperature rise since 1900, it fails to explain a rise of 0.4 °C since 1980. "The curves diverge after 1980," Thejll said, "and it's a startlingly large deviation. Something else is acting on the climate.... It has the fingerprints of the greenhouse effect."^[24]

Later that same year, Peter Stott and other researchers at the Hadley Centre in the United Kingdom published a paper in which they reported on the most comprehensive model simulations to date of the climate of the 20th century. Their study looked at both "natural forcing agents" (solar variations and volcanic emissions) as well as "anthropogenic forcing" (greenhouse gases and sulphate aerosols). They found that "solar effects may have contributed significantly to the warming in the first half of the century although this result is dependent on the reconstruction of total solar irradiance that is used. In the latter half of the century, we find that anthropogenic increases in greenhouses gases are largely responsible for the observed warming, balanced by some cooling due to anthropogenic sulphate aerosols, with no evidence for significant solar effects." Stott's team found that combining all of these factors enabled them to closely simulate global temperature changes throughout the 20th century. They predicted that continued greenhouse gas emissions would cause additional future temperature increases "at a rate similar to that observed in recent decades". It should be noted that their solar forcing included "spectrally-resolved changes in solar irradiance" and not the indirect effects mediated through cosmic rays for which there is still no accepted mechanism — these ideas are still being fleshed out. Cosmic Rays, Clouds, and Climate, K. S. Carslaw, R. G. Harrison, and J. Kirkby Science Nov 29 2002: 1732-1737 and those articles citing it.^[25] In addition, the study notes "uncertainties in historical forcing" — in other words, past natural forcing may still be having a delayed warming effect, most likely due to the oceans.^[26] A graphical representation^[27] of the relationship between natural and anthropogenic factors contributing to climate change appears in "Climate Change 2001: The Scientific Basis", a report by the Intergovernmental Panel on Climate Change (IPCC).^[28] IPCC is science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the risk of human-induced climate change. The Panel is open to all...

It should be noted that Stott's 2003 work mentioned in the model section above largely revised his assessment, and found a significant solar contribution to recent warming, although still smaller than that of the green house gases.^[18]

See also

• Global dimming

NASA photograph showing aircraft contrails and natural clouds. ...

References

General references

• C. G. Abbot (1966). "SOLAR VARIATION, A WEATHER ELEMENT". Proc Natl Acad Sci U S A. 56 (6): 1627-1634.
• The Sun and Climate. U.S. Geological Survey Fact Sheet 0095-00. Retrieved on February 21, 2005.
• The Sun's role in Climate Changes. Proc. of The International Conference on Global Warming and The Next Ice Age, 19-24 August, 2001, Halifax, Nova Scotia.. Retrieved on February 21, 2005.
• Warren B. White, Judith Lean, Daniel R. Cayan and Michael D. Dettinger (1997). "Response of global upper ocean temperature to changing solar irradiance". J. Geophys. Res. 102 (C2): 3255-3266.
• Foukal et al., 1977, "The effects of sunspots and faculae on the solar constant", Astrophys. J., 215, 952.
• Dziembowski, W.A., P.R. Goode, and J. Schou, 2001: Does the sun shrink with increasing magnetic activity? Astrophysical Journal, 553, 897-904

February 21 is the 52nd day of the year in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... February 21 is the 52nd day of the year in the Gregorian Calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

Footnotes

1. ^ Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present. Retrieved on October 5, 2005.
2. ^ Solar Forcing of Climate. Climate Change 2001: Working Group I: The Scientific Basis. Retrieved on March 10, 2005.
3. ^ ^{a b} Changing Sun, Changing Climate?. The Discovery of Global Warming. Retrieved on February 21, 2005.
4. ^ Great Moments in the History of Solar Physics 1. Great Moments in the History of Solar Physics. Retrieved on March 19, 2006.
5. ^ Solanki, S.K., I.G. Usoskin, B. Kromer, M. Schussler and J. Beer (2004). "Unusual activity of the Sun during recent decades compared to the previous 11,000 years". Nature 431 (7012): 1084-1087. DOI:10.1038/nature02995., 11,000 Year Sunspot Number Reconstruction. Global Change Master Directory. Retrieved on March 11, 2005.
6. ^ Charles A. Perry and Kenneth J. Hsudagger (2000). "Geophysical, archaeological, and historical evidence support a solar-output model for climate change". PNAS 97 (23): 12433-12438. DOI:10.1073/pnas.230423297.
7. ^ What the Sunspot Record Tells Us about Space Climate. Submitted to Solar Physics 2004/08/31. Retrieved on March 11, 2005.
8. ^ SOLAR VARIABILITY: climatic change resulting from changes in the amount of solar energy reaching the upper atmosphere.. INTRODUCTION TO QUATERNARY ECOLOGY. Retrieved on March 11, 2005.
9. ^ Henrik Svensmark (1998). "Influence of Cosmic Rays on Earth's Climate". Physical Review Letters 81 (22): 5027-5030.
10. ^ Atmospheric Ionization and Clouds as Links Between Solar Activity and Climate. Tinsley, Brian A. and Fangqun Yu, in: Solar Variability and Its Effects on the Earth's Atmospheric and Climate System. Retrieved on March 10, 2005. Judit M. Pap and Peter Fox (2004). Solar Variability and Its Effects on the Earth's Atmospheric and Climate System. American Geophysical Union. ISBN 0-87590-406-8.
11. ^ E. Pallé, C.J. Butler, K. O'Brien (2004). "The possible connection between ionization in the atmosphere by cosmic rays and low level clouds". Journal of Atmospheric and Solar-Terrestrial Physics 66 (18): 1779-1720. DOI:10.1016/j.jastp.2004.07.041.
12. ^ Pallé, E. (2005). "Possible satellite perspective effects on the reported correlations between solar activity and clouds". Geophys. Res. Lett. 32 (3): L03802. DOI:10.1029/2004GL021167.
13. ^ Variations in CO2 Growth Rate Associated with Solar Activity. Still Waiting for Greenhouse. Retrieved on March 10, 2005.
14. ^ ^{a b} Climate Change 2001: Working Group I: The Scientific Basis. Intergovernmental Panel on Climate Change. Retrieved on 2006-04-02.
15. ^ USGCRP Seminar: What's Driving Climate Change in the 20th Century - Changes in Solar Radiation or the Buildup of Greenhouse Gases?. Retrieved on October 5, 2005.
16. ^ Climate Change 2001: The Scientific Basis. Retrieved on October 5, 2005.
17. ^ Welcome to AGU Online Services. Retrieved on October 5, 2005.
18. ^ ^{a b} Stott, Peter A., Gareth S. Jones and John F. B. Mitchell (15 December 2003). "Do Models Underestimate the Solar Contribution to Recent Climate Change". Journal of Climate 16: 4079-4093. Retrieved on October 5.
19. ^ Hotter-burning sun warming the planet - The Washington Times: World - July 19, 2004. Retrieved on October 5, 2005.
20. ^ How Strongly Does the Sun Influence the Global Climate? Studies at the Max Planck Institute for Solar System Research reveal: solar activity affects the climate but plays only a minor role in the current global warming. Retrieved on October 5, 2005.
21. ^ ^{a b} Damon, Paul E., Paul Laut (28 September 2004). "Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate Data". Eos 85 (39): 370-374. Retrieved on October 5.
22. ^ http://solar-center.stanford.edu/images/solactivity.jpg. Retrieved on October 5, 2005.
23. ^ Brightening Sun is Warming Earth. Retrieved on October 5, 2005.
24. ^ New Scientist Premium- Don't blame the Sun - This Week. Retrieved on October 5, 2005.
25. ^ Cosmic Rays, Clouds, and Climate, K. S. Carslaw, R. G. Harrison, and J. Kirkby Science Nov 29 2002: 1732-1737 and those articles citing it. Retrieved on October 5, 2005.
26. ^ Stott et al. (2000). "External Control of 20th Century Temperature by Natural and Anthropogenic Fo...". Science 290: 2133–2137.
27. ^ graphical representation. Retrieved on October 5, 2005.
28. ^ Climate Change 2001: The Scientific Basis. Retrieved on October 5, 2005.

• ↑  Climate Change 2001: The Scientific Basis. Retrieved on October 5, 2005.
• ↑  Nir J. Shaviv, Ján Veizer. Celestial driver of Phanerozoic climate?. JULY 2003, GSA TODAY. Retrieved on October 3, 2005.
• ↑  http://www.soest.hawaii.edu/GG/FACULTY/POPP/Rahmstorf%20et%20al.%202004%20EOS.pdf. Retrieved on October 5, 2005.

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