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| '''Solar variation''' is the change in the amount of ] emitted by the ] (see ]) and in its spectral distribution over years to millennia. These variations have periodic components, the main one being the approximately 11-year ] (or ] cycle). The changes also have ] fluctuations.<ref name="ACRIM">Active Cavity Radiometer Irradiance Monitor (ACRIM) (Satellite observations of total solar irradiance); access date 2012-02-03</ref> In recent decades, solar activity has been measured by satellites, while before it was estimated using ]. Scientists studying ] are interested in understanding the effects of variations in the total and spectral solar irradiance on Earth and its ]. | |||
| Variations in total ] were too small to detect with technology available before the satellite era, although the small fraction in ] has recently been found to vary significantly more than previously thought over the course of a solar cycle.<ref name="SolarForcing">{{cite journal | title=Solar forcing of winter climate variability in the Northern Hemisphere | journal=] |date=9 October 2011 |author=Ineson S., Scaife A.A., Knight J.R., Manners J.C., Dunstone N.J., Gray L.J., Haigh J.D. |volume=4 |pages=753–7 |doi=10.1038/ngeo1282 |url=http://www.nature.com/ngeo/journal/v4/n11/full/ngeo1282.html | issue=11 | bibcode=2011NatGe...4..753I}}</ref> Total solar output is now measured to vary (over the last three 11-year ] cycles) by approximately 0.1%,<ref name=Willson91>{{cite journal |last=Willson |first=Richard C.|author2=H.S. Hudson|year=1991 |title=The Sun's luminosity over a complete solar cycle |journal=Nature |volume=351 |issue=6321 |pages=42–4 | doi=10.1038/351042a0 |url=http://www.nature.com/nature/journal/v351/n6321/abs/351042a0.html |ref=harv |bibcode=1991Natur.351...42W}}<!-- {{harvnb|Willson|1991}} --></ref><ref name="IPCCtarWG1244">{{cite web | title=Solar Forcing of Climate | work=Climate Change 2001: Working Group I: The Scientific Basis | url=http://www.grida.no/climate/ipcc_tar/wg1/244.htm | accessdate = 2005-03-10}}</ref><ref name="Weart">{{Cite book | first=Spencer | last=Weart | author-link=Spencer R. Weart | title=The Discovery of Global Warming | chapter=Changing Sun, Changing Climate? | publisher=Harvard University Press | year=2003 | isbn=0-674-01157-0 | url=http://www.aip.org/history/climate/ | chapter-url=http://www.aip.org/history/climate/solar.htm | accessdate=17 April 2008 }}</ref> or about 1.3 ]s per square meter (W/m<sup>2</sup>) peak-to-trough from ] to ] during the 11-year sunspot cycle. The amount of ] received at the outer limits of Earth's ] averages 1366 W/m<sup>2</sup>.<ref name="ACRIM" /><ref>{{cite journal |last1=Willson |first1=R. C. |first2=A. V. |last2=Mordvinov |title=Secular total solar irradiance trend during solar cycles 21–23 |journal=Geophys. Res. Lett. |volume=30 |issue=5 |year=2003 |doi=10.1029/2002GL016038 |url=http://www.agu.org/journals/gl/gl0905/2008GL036307 |pages=1199 |bibcode=2003GeoRL..30e...3W}}</ref><ref name="www.pmodwrc.ch.91">{{cite web | title=Construction of a Composite Total Solar Irradiance (TSI) Time Series from 1978 to present | url=http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant | publisher=Physikalisch-Meteorologisches Observatorium Davos (PMOD)| accessdate = 2005-10-05}}</ref> No direct measurements of the longer-term variation are available, while proxy measure interpretations of variations differ. The intensity of solar radiation reaching Earth has been relatively constant through the last 2000 years, with variations estimated at around 0.1–0.2%.<ref name="NASreportsurftemp">{{Cite book | chapter-url=http://books.nap.edu/openbook.php?record_id=11676&page=102 | chapter=Climate Forcings and Climate Models | title=Surface Temperature Reconstructions for the Last 2,000 Years | url=http://www.nap.edu/catalog.php?record_id=11676 | publisher=] | year=2006 | isbn=0-309-10225-1 | accessdate=1 February 2012 | editor1-first=Gerald R. | editor1-last=North | editor2-first=Franco | editor2-last=Biondi | editor3-first=Peter | editor3-last=Bloomfield | editor4-first=John R. | editor4-last=Christy | editor4-link=John Christy | displayeditors = 3| author=Committee on Surface Temperature Reconstructions for the Last 2,000 Years, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, National Research Council of the National Academies. }}</ref><ref name="lean2000">{{Cite journal | first1=Judith | last1=Lean | title=Evolution of the Sun's Spectral Irradiance Since the Maunder Minimum | url=ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/solar_variability/lean2000_irradiance.txt | year=2000 | journal=Geophysical Research Letters | volume=27 | issue=16 | pages=2425–8 | doi=10.1029/2000GL000043 | bibcode=2000GeoRL..27.2425L}}</ref><ref name=Scafetta06>{{cite journal |last1=Scafetta |first1=N. |first2=B. J. |last2=West |title=Phenomenological solar signature in 400 years of reconstructed Northern Hemisphere temperature record |journal=Geophys. Res. Lett. |volume=33 |issue=17 |pages=L17718 |year=2006 |doi=10.1029/2006GL027142 |url=http://www.agu.org/journals/gl/gl0617/2006GL027142/ |bibcode=2006GeoRL..3317718S}}</ref> Solar variation, together with ] are hypothesized to have contributed to climate change, for example during the ]. Changes in solar brightness are considered to be too weak to explain recent ].<ref name="UCARbrightness">{{cite pressrelease | title=Changes in Solar Brightness Too Weak To Explain Global Warming | publisher=] | url=http://www.ucar.edu/news/releases/2006/brightness.shtml |date=13 September 2006 | accessdate=18 April 2007 }}</ref> | |||
| <!-- | |||
| Commented out: "Apart from solar brightness variations, Earth's climate might be influenced by ] or the Sun's ultraviolet radiation, but these effects are not yet well understood." - Out of place in intro for "Solar variation" article. | |||
| Commented out: </ref>]] --> | |||
| == History of study into solar variations == | |||
| ].]] | |||
| The longest recorded aspect of solar variations are changes in ]s. 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, ]s began using ]s to observe sunspots. Initial study focused on their nature and behavior.<ref name="solargreat">{{cite web | title=Great Moments in the History of Solar Physics 1| work =Great Moments in the History of Solar Physics | url=http://web.hao.ucar.edu/public/education/sp/great_moments.html| accessdate = 2006-03-19 |archiveurl = http://web.archive.org/web/20060301083022/http://web.hao.ucar.edu/public/education/sp/great_moments.html |archivedate = 1 March 2006}}</ref> Although the physical aspects of sunspots were not identified until the 20th century, observations continued. Study was hampered during the 17th century due to the low number of sunspots during what is now recognized as an extended period of low solar activity, known as the ]. By the 19th century, then-sufficient sunspot records allowed researchers to infer periodic cycles in sunspot activity. In 1845, ] and ] observed the Sun with a ] and determined that sunspots emitted less radiation than surrounding areas. The emission of higher than average amounts of radiation later were observed from the solar ]e.<ref>{{cite journal |last=Arctowski |first=Henryk |year=1940 |title=On Solar Faculae and Solar Constant Variations |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=26 |issue=6 |pages=406–11 |doi=10.1073/pnas.26.6.406|url=http://www.pnas.org/cgi/reprint/26/6/406.pdf |format=PDF |pmid=16588370 |pmc=1078196|bibcode = 1940PNAS...26..406A }}</ref> | |||
| Around 1900, researchers began to explore connections between solar variations and Earth's weather. ] (SAO) assigned ] and his team to detect changes in the radiation of the Sun. They began by inventing instruments to measure solar radiation. Later, when Abbot was SAO head, they established a solar station at ] to complement its data from ]. He detected 27 harmonic periods within the 273-month ]s, 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 urban temperature and precipitation trends. With the advent of ], scientists such as Glock attempted to connect variation in tree growth to periodic solar variations and infer long-term secular variability in the ] from similar variations in millennial-scale chronologies.<ref name="frits">{{cite book |author=Fritts, Harold C. |title=Tree rings and climate |publisher=Academic Press |location=Boston |year=1976 |isbn=0-12-268450-8 }}</ref> | |||
| Statistical studies that correlate ] and ] with solar activity date back at least to 1801, when ] noted an apparent connection between wheat prices and sunspot records.<ref>{{cite web | |||
| | url= http://www.hao.ucar.edu/Public/education/bios/herschel.html | |||
| | title= William Herschel (1738–1822) | |||
| | publisher= ] | |||
| | accessdate= 2008-02-27 |archiveurl = http://web.archive.org/web/20070607215435/http://www.hao.ucar.edu/Public/education/bios/herschel.html |archivedate = 7 June 2007}}</ref> They now often involve high-density global datasets compiled from surface networks and ] observations and/or the forcing of ]s with synthetic or observed solar variability to investigate the detailed processes by which the effects of solar variations propagate through the Earth's climate system.<ref>{{Cite journal | first1=Charles D. | last1=Camp | first2=Ka-Kit | last2=Tung | title=The Influence of the Solar Cycle and QBO on the Late Winter Stratospheric Polar Vortex | url=http://www.amath.washington.edu/research/articles/Tung/journals/camp-tung-0721-revised.pdf|format=PDF| year=2006 | journal=] | volume=87 | issue=52 | pages=Fall Meet. Suppl., Abstract #A11B–0862 | accessdate=28 April 2009 | doi=10.1029/2006EO300005 | last3=Quinif | first3=Yves | last4=Kaufman | first4=Olivier | last5=Van Ruymbeke | first5=Michel | last6=Vandiepenbeeck | first6=Marc | last7=Camelbeeck | first7=Thierry | bibcode=2006EOSTr..87..298V}}</ref> | |||
| ==Solar activity and irradiance measurement== | |||
| Direct irradiance measurements have only been available during the last three cycles and are based on a composite of multiple observing satellites.<ref name="ACRIM" /><ref></ref> However, the correlation between irradiance measurements and other proxies of solar activity make it reasonable to estimate past solar activity. Most important among these proxies is the record of sunspot observations that has been recorded since ~1610. Since sunspots and associated ] are directly responsible for small changes in the brightness of the sun,{{Citation needed|date=November 2011}} they are closely correlated to changes in solar output. Direct measurements of radio emissions from the Sun at 10.7 cm wavelength also provide a proxy of solar activity that can be measured from the ground since the Earth's atmosphere is transparent to radiation at this wavelength. Lastly, ] can impact human life on ] by affecting electrical systems, especially ]s. Flares usually occur in the presence of sunspots, and hence the two are correlated, but flares themselves make only tiny perturbations of the solar ]. | |||
| Recently it has been claimed that the total solar irradiance is varying in ways that are not duplicated by changes in sunspot observations or radio emissions, though Willson, DeWitte, and others have pointed out that these shifts in irradiance may be no more than the result of calibration problems in the measuring satellites.<ref>{{cite journal|doi=10.1029/2002GL016038|title=Secular total solar irradiance trend during solar cycles 21–23|author=Richard C. Willson, Alexander V. Mordvinov|year=2003|journal=Geophysical Research Letters|volume=30|issue=5|pages=1199|bibcode=2003GeoRL..30e...3W}}</ref><ref>{{cite journal|doi = 10.1007/s11207-005-5698-7|journal = Solar Physics|year=2004|volume=224|issue = 1–2|pages= 209–216|title=Measurement and uncertainty of the long-term total solar irradiance trend|author=Steven DeWitte, Dominiqu Crommelynck, Sabri Mekaoui, and Alexandre Joukoff|bibcode = 2004SoPh..224..209D }}</ref> These speculations also admit the possibility that a long-term trend might exist in solar irradiance.<ref>{{cite journal|author=Fröhlich, C. and J. Lean|year=2004|title=Solar Radiative Output and its Variability: Evidence and Mechanisms|journal=Astronomy and Astrophysical Review|volume=12|issue=4|pages=273–320|doi=10.1007/s00159-004-0024-1|bibcode = 2004A&ARv..12..273F }}</ref> | |||
| === Sunspots === | |||
| {{Main|Sunspot}} | |||
| ] | |||
| ]s are relatively dark areas on the radiating 'surface' (]) of the Sun where intense magnetic activity inhibits convection and cools the ]. ] are slightly brighter areas that form around sunspot groups as the flow of energy to the photosphere is re-established and both the normal flow and the sunspot-blocked energy elevate the radiating 'surface' temperature. Scientists have speculated on possible relationships between sunspots and solar luminosity since the historical sunspot area record began in the 17th century.<ref>{{cite journal |author=Eddy, J.A. |title=Samuel P. Langley (1834–1906) |journal=Journal for the History of Astronomy |volume=21 |issue= |pages=111–20 |year=1990 |url=http://www.hao.ucar.edu/Public/education/bios/langley.html |bibcode = 1990JHA....21..111E }} {{Dead link|date=January 2010}}</ref><ref>{{cite journal |first1=P. V. |last1=Foukal |first2=P. E. |last2=Mack |first3=J. E. |last3=Vernazza |title=The effect of sunspots and faculae on the solar constant |journal=The Astrophysical Journal |volume=215 |year=1977 |doi=10.1086/155431 |pages=952 |bibcode=1977ApJ...215..952F}}</ref> Decreases in luminosity caused by sunspots (generally < - 0.3%) is correlated with increases (generally < + 0.05%) caused both by faculae that are associated with active regions as well as the magnetically active 'bright network'.<ref name=Willson81/> | |||
| Modulation of the solar luminosity by magnetically active regions was confirmed by satellite measurements of total solar irradiance (TSI) by the ACRIM1 experiment on the ] (launched in 1980).<ref name=Willson81/> The modulations were later confirmed in the results of the ERB experiment launched on the Nimbus 7 satellite in 1978.<ref>{{cite journal |author=J. R. Hickey, B. M. Alton, H. L. Kyle and E. R. Major |title=Observation of total solar irradiance (TSI) variability from Nimbus satellites |journal=Advances in Space Research |volume=8 |issue=7 |pages=5–10 |year=1988 |doi=10.1016/0273-1177(88)90164-0 |bibcode = 1988AdSpR...8....5H }}</ref> Satellite observation was continued by ACRIM-3 and other satellites.<ref name="ACRIM" /> ] in magnetically active regions are cooler and 'darker' than the average ] and cause temporary decreases in TSI of as much as 0.3%. ] in magnetically active regions are hotter and 'brighter' than the average ] and cause temporary increases in TSI. | |||
| The net effect during periods of enhanced solar magnetic activity is increased radiant solar output because faculae are larger and persist longer than sunspots. Conversely, periods of lower solar magnetic activity and fewer sunspots (such as the Maunder Minimum) may correlate with times of lower terrestrial irradiance from the sun.<ref>Rodney Viereck, NOAA Space Environment Center. </ref> | |||
| Data mostly from the Michelson Doppler Imager instrument on ], show changes in solar diameter to be about 0.001%, much less than the effect of magnetic activity changes.<ref>{{Cite journal|title = Oscillations of alpha UMa and other red giants|url = http://arxiv.org/abs/astro-ph/0108337|journal = Monthly Notices of the Royal Astronomical Society|date = 2001-12-01|issn = 0035-8711|pages = 601-610|volume = 328|issue = 2|doi = 10.1046/j.1365-8711.2001.04894.x|first = W. A.|last = Dziembowski|first2 = D. O.|last2 = Gough|first3 = G.|last3 = Houdek|first4 = R.|last4 = Sienkiewicz}}</ref> | |||
| Various studies used sunspot number to estimate solar output and calibrated ground instruments by comparison with high-altitude and orbital instruments. Others combined later readings and factors to adjust historical data. Other proxy data – such as the abundance of ] isotopes – have been used to infer solar magnetic activity and thus likely brightness. Sunspot activity has been measured using the ''']''' for about 300 years. This index (also known as the '''Zürich number''') uses both the number of sunspots and the number of groups of sunspots to compensate for variations in measurement. A 2003 study found that sunspots had been more frequent since the 1940s than in the previous 1150 years.<ref>{{Cite journal | |||
| | first1=Ilya G.| last1=Usoskin | |||
| | first2=Sami K.| last2=Solanki | |||
| | first3=Manfred| last3=Schüssler | |||
| | first4=Kalevi | last4=Mursula | |||
| | first5=Katja | last5= Alanko | |||
| | author2-link=Sami Solanki | |||
| | title=A Millennium Scale Sunspot Number Reconstruction: Evidence For an Unusually Active Sun Since the 1940’s | |||
| | journal=] | |||
| | volume=91 | year=2003 | |||
| | arxiv=astro-ph/0310823 | |||
| | issue=21 | |||
| | doi=10.1103/PhysRevLett.91.211101 | |||
| | pages=211101 | bibcode=2003PhRvL..91u1101U | |||
| }}</ref> | |||
| ] | |||
| Sunspot numbers over the past 11,400 years have been reconstructed using ]-based ] (tree ring dating). The level of solar activity during the past 70 years is exceptional – the last period of similar magnitude occurred around 9,000 years ago (during the warm ]).<ref name="Usoskin07"/><ref name="Solanski2004">{{Cite journal | first1=Sami K.| last1=Solanki | author-link=Sami Solanki | first2=Ilya G.| last2=Usoskin | first3=Bernd | last3=Kromer | first4=Manfred| last4=Schüssler | first5=Jürg | last5=Beer | title=Unusual activity of the Sun during recent decades compared to the previous 11,000 years | journal=Nature | volume=431 | year=2004 | pages=1084–7 | url=http://cc.oulu.fi/%7Eusoskin/personal/nature02995.pdf | format=PDF | doi=10.1038/nature02995 | accessdate=17 April 2007 | pmid=15510145 | issue=7012 | bibcode=2004Natur.431.1084S}}, {{cite web | title=11,000 Year Sunspot Number Reconstruction | work=Global Change Master Directory | url=http://gcmd.nasa.gov/KeywordSearch/Metadata.do?Portal=GCMD&KeywordPath=%5BParameters%3ACategory%3D%27EARTH+SCIENCE%27%2CTopic%3D%27SUN-EARTH+INTERACTIONS%27%2CTerm%3D%27SOLAR+ACTIVITY%27%2CVariable%3D%27SUNSPOTS%27%5D&OrigMetadataNode=GCMD&EntryId=NOAA_NCDC_PALEO_2005-015&MetadataView=Brief&MetadataType=0&lbnode=gcmd3b | accessdate = 2005-03-11}}</ref> 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.<ref name="Solanski2004"/> | |||
| ] | |||
| {| class="wikitable" | |||
| |+ '''Solar activity events and approximate dates''' | |||
| |- | |||
| ! Event !! Start !! End | |||
| |- | |||
| | Homeric minimum<ref name="SedimentStudy">{{cite journal | title=Regional atmospheric circulation shifts induced by a grand solar minimum | journal=] |date=2 April 2012 |author=Celia Martin-Puertas, Katja Matthes, Achim Brauer, Raimund Muscheler, Felicitas Hansen, Christof Petrick, Ala Aldahan, Göran Possnert & Bas van Geel |volume=5 |pages=397–401 |doi=10.1038/ngeo1460 |url=http://www.nature.com/ngeo/journal/v5/n6/full/ngeo1460.html | issue=6 |bibcode = 2012NatGe...5..397M }}</ref> || 950BC || 800BC | |||
| |- | |||
| | Oort minimum || 1040 || 1080 | |||
| |- | |||
| | Medieval maximum || 1100 || 1250 | |||
| |- | |||
| | Wolf minimum || 1280 || 1350 | |||
| |- | |||
| | ] || 1450 || 1550 | |||
| |- | |||
| | ] || 1645 || 1715 | |||
| |- | |||
| | ] || 1790 || 1820 | |||
| |- | |||
| | ] || 1900 || present | |||
| |} | |||
| A list of historical Grand minima of solar activity<ref name="Usoskin07">{{Cite journal | first1=Ilya G.| last1=Usoskin | first2=Sami K.| last2=Solanki | first3=Gennady A. | last3=Kovaltsov | title=Grand minima and maxima of solar activity: new observational constraints | journal= Astron. Astrophys. | volume=471 | issue=1 | pages=301–9 | url=http://cc.oulu.fi/~usoskin/personal/aa7704-07.pdf | format=PDF | doi=10.1051/0004-6361:20077704 | year=2007 | bibcode=2007A&A...471..301U|arxiv = 0706.0385 }}</ref> includes also Grand minima ca. 690 AD, 360 BC, 770 BC, 1390 BC, 2860 BC, 3340 BC, 3500 BC, 3630 BC, 3940 BC, 4230 BC, 4330 BC, 5260 BC, 5460 BC, 5620 BC, 5710 BC, 5990 BC, 6220 BC, 6400 BC, 7040 BC, 7310 BC, 7520 BC, 8220 BC, 9170 BC. | |||
| ===Solar cycles=== | |||
| {{Main|Solar cycle}} | |||
| The sun undergoes various quasi-periodic changes. Only the 11 and closely related 22-year cycles are clear in the observations. | |||
| * 11 years: Most obvious is a gradual increase and more rapid decrease of the number of sunspots over a period ranging from 9 to 12 years, called the ], named after ]. Differential rotation of the sun's convection zone (as a function of latitude) consolidates magnetic flux tubes, increases their ] strength and makes them buoyant (see ]). As they rise through the solar atmosphere they partially block the convective flow of energy, cooling their region of the ], causing ']'. The Sun's apparent surface, the photosphere, radiates more actively when there are more sunspots. Satellite monitoring of ] since 1980 has shown there is a direct relationship between the Schwabe cycle and luminosity with a solar cycle peak-to-peak amplitude of about 0.1%.<ref name=Willson91/> Luminosity has also been found to decrease by as much as 0.3% on a 10-day timescale when large groups of sunspots rotate across the Earth's view and increase by as much as 0.05% for up to 6 months due to ] associated with the large sunspot groups.<ref name=Willson81>{{Cite journal |author=Willson RC, Gulkis S, Janssen M, Hudson HS, Chapman GA |title=Observations of Solar Irradiance Variability |journal=Science |volume=211 |issue=4483 |pages=700–2 |date= February 1981|pmid=17776650 |doi=10.1126/science.211.4483.700 |url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=17776650|bibcode = 1981Sci...211..700W }}</ref> | |||
| * 22 years: During the ], named after ], the magnetic field of the Sun reverses during each Schwabe cycle, so the magnetic poles return to the same state after two reversals. | |||
| ] | |||
| ===Hypothesized cycles=== | |||
| Periodicity of solar activity with periods longer than the sunspot cycle has been proposed, including: | |||
| * 87 years (70–100 years): ''Gleissberg cycle'', named after Wolfgang Gleißberg, is thought to be an amplitude modulation of the Schwabe Cycle,<ref>{{cite journal |first1=C. P. |last1=Sonett |first2=S. A. |last2=Finney |first3=A. |last3=Berger |title=The Spectrum of Radiocarbon |journal=] |volume=330 |issue=1615 |pages=413–26 |date=24 April 1990 |doi=10.1098/rsta.1990.0022 |bibcode = 1990RSPTA.330..413S }}</ref><ref name=Braun05>{{cite journal |title=Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model |journal=Nature |volume=438 |pages=208–11 |date=10 November 2005 |doi=10.1038/nature04121 |url=http://www.awi.de/fileadmin/user_upload/Research/Research_Divisions/Climate_Sciences/Paleoclimate_Dynamics/Modelling/Methods/PossibleSolar.pdf |pmid=16281042 |last1=Braun |first1=H |last2=Christl |first2=M |last3=Rahmstorf |first3=S |last4=Ganopolski |first4=A |last5=Mangini |first5=A |last6=Kubatzki |first6=C |last7=Roth |first7=K |last8=Kromer |first8=B |issue=7065|bibcode = 2005Natur.438..208B }}</ref> | |||
| * 210 years: ''Suess cycle'' (a.k.a. "de Vries cycle"). Braun, ''et al.'', (2005).<ref name=Braun05/> | |||
| * 2,300 years: ''Hallstatt cycle''<ref>{{cite web |url=http://pubs.usgs.gov/fs/fs-0095-00/fs-0095-00.pdf |title=The Sun and Climate |format=PDF |work=U.S. Geological Survey |id=Fact Sheet 0095-00}}</ref><ref>{{cite journal |first1=S. S. |last1=Vasiliev |first2=V. A. |title=The ~ 2400-year cycle in atmospheric radiocarbon concentration: bispectrum of <sup>14</sup>C data over the last 8000 years |journal=ANGEO |volume=20 |issue=1 |pages=115–20 |year=2002 |url=http://www.ann-geophys.net/20/115/2002/angeo-20-115-2002.pdf | doi = 10.5194/angeo-20-115-2002 |last2=Dergachev|bibcode = 2002AnGeo..20..115V }}</ref> | |||
| * 6000 years<ref>{{Cite journal |first1=M. A. |last1=Xapsos |first2=E. A. |last2=Burke |title=Evidence of 6 000-Year Periodicity in Reconstructed Sunspot Numbers |journal=Solar Physics |volume=257 |issue=2 |pages=363–9 |date= July 2009|doi=10.1007/s11207-009-9380-3 |bibcode = 2009SoPh..257..363X }}</ref> | |||
| Other patterns have been detected: | |||
| * In ]: 105, 131, 232, 385, 504, 805, 2,241 years.<ref>{{Cite journal|title = The Sun as a low-frequency harmonic oscillator.|url = https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1450|journal = Radiocarbon|date = 2006/03/31|issn = 0033-8222|pages = 199-205|volume = 34|issue = 2|doi = 10.2458/azu_js_rc.34.1450|first = Paul E.|last = Damon|first2 = John L.|last2 = Jirikowic}}</ref> | |||
| * During the ] 240 million years ago, mineral layers created in the Castile Formation show cycles of 2,500 years.{{Citation needed|date = July 2015}} | |||
| ====Predictions based on patterns==== | |||
| * Perry and Hsu (2000) proposed a simple model based on emulating harmonics by multiplying the basic 11-year cycle by powers of 2, which produced results similar to ] behavior. Extrapolation suggests a gradual cooling during the next few centuries with intermittent minor warmups and a return to near ] 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.<ref name="Perry2000">{{Cite journal | first1=Charles A. | last1=Perry | first2=Kenneth J. | last2=Hsu | title=Geophysical, archaeological, and historical evidence support a solar-output model for climate change | doi=10.1073/pnas.230423297 | journal=Proc. Natl. Acad. Sci. U.S.A. | volume=97 | year=2000 | pages=12433–8 | url=http://www.pnas.org/cgi/reprint/97/23/12433.pdf |format=PDF | last3=Usoskin|first3=Ilya G. | pmid=11050181 | issue=23 | pmc=18780 |bibcode = 2000PNAS...9712433P }}</ref> | |||
| * The Gleisberg cycle's 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.<ref name="Hathaway2005">{{Cite journal | first1=David H. | last1=Hathaway | first2=Robert M. | last2=Wilson | title=What the Sunspot Record Tells Us About Space Climate | journal=] | volume=224 | issue=1–2 | year=2004 | pages=5–19 | doi=10.1007/s11207-005-3996-8 | url=http://science.msfc.nasa.gov/ssl/pad/solar/papers/hathadh/HathawayWilson2004.pdf |format=PDF| accessdate=19 April 2007 | archiveurl = http://web.archive.org/web/20060104223339/http://science.msfc.nasa.gov/ssl/pad/solar/papers/hathadh/HathawayWilson2004.pdf |archivedate = 4 January 2006|bibcode = 2004SoPh..224....5H }}</ref>{{Update section|date = July 2015}} | |||
| * Because carbon-14 cycles are quasi periodic, Damon and Sonett (1989) predict future climate:<ref name="AZgeos462climsolar">{{cite web | title=Solar Variability: climatic change resulting from changes in the amount of solar energy reaching the upper atmosphere. |work=Introduction to Quaternary Ecology | url=http://www.geo.arizona.edu/palynology/geos462/20climsolar.html | accessdate = 2005-03-11}} | |||
| </ref> | |||
| ] | |||
| Solar ] and ] are measures of the amount of sunlight that reaches the Earth. The equipment used might measure optical brightness, total radiation, or radiation in various frequencies. Historical estimates use various measurements and proxies. | |||
| {| class="wikitable" | |||
| ! Cycle length !! Cycle name !! Last positive <br/> carbon-14 anomaly !! Next "warming" | |||
| |- | |||
| | 232 || --?-- || AD 1922 (cool) || AD 2038 | |||
| |- | |||
| | 208 || Suess || AD 1898 (cool) || AD 2210 | |||
| |- | |||
| | 88 || Gleisberg || AD 1986 (cool) || AD 2030 | |||
| |} | |||
| ===Solar irradiance of Earth and its surface=== | |||
| ] | |||
| There are two common meanings for solar ]: | |||
| * 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. Measurements above the atmosphere are needed to determine variations in solar output, to avoid the confounding effects of changes within the atmosphere. There is some evidence that sunshine at the Earth's surface has been decreasing in the last 50 years (see ]) possibly caused by increased atmospheric pollution, whilst over roughly the same timespan solar output has been nearly constant. | |||
| ====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 latitudinal distribution of radiation. These orbital changes or ] 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 '']''. | |||
| ==Changes in solar interactions with Earth== | |||
| {{multiple image|direction=vertical|width=220| footer = Multiple factors have affected terrestrial ], including ] and ] on top of any effects of solar variability.|image1=NASAdata1979to2009.jpg|caption1='''1979–2009:''' Over the past 3 decades, terrestrial temperature has not correlated with sunspot trends. The top plot is of sunspots, while below is the global atmospheric temperature trend. ] and ] were volcanoes, while ] is part of ]. The effect of greenhouse gas emissions is on top of those fluctuations.}} | |||
| Several hypotheses describe how solar variations may affect Earth. Some variations, such as changes in the size of the Sun, are only of interest in the field of ]. | |||
| ===Total irradiance=== | |||
| * Total solar irradiance (TSR) changes slowly on decadal and longer timescales. | |||
| * The variation during recent solar magnetic activity cycles is about 0.1% (peak-to-peak).<ref name=Willson91/> | |||
| * Variations corresponding to solar changes with periods of 9–13, 18–25, and >100 years have been detected in sea-surface temperatures. | |||
| * In contrast to older reconstructions,<ref name="books.nap.edu">{{cite book |title=Solar Influences on Global Change |publisher=National Academy Press |location=Washington, D.C |year=1994 |page=36 |isbn=0-309-05148-7 |url=http://books.nap.edu/openbook.php?record_id=4778&page=R1 |author=Board on Global Change, Commission on Geosciences, Environment, and Resources, National Research Council.}}</ref> most recent TSR reconstructions point to an increase of only about 0.05% to 0.1% between Maunder Minimum and the present.<ref>{{cite journal |last1=Wang |first1=Y.-M. |last2=Lean |first2=J. L. |last3=Sheeley |first3=N. R. |title=Modeling the Sun's magnetic field and irradiance since 1713 |journal=The Astrophysical journal |volume=625 |issue=1 |pages=522–38 |year=2005 |doi=10.1086/429689 |url=http://www.climatesci.org/publications/pdf/Wang_2005.pdf |bibcode=2005ApJ...625..522W}}</ref><ref>{{cite journal |first1=N. A. |last1=Krivova |first2=L. |last2=Balmaceda |first3=S. K. |last3=Solanki |title=Reconstruction of solar total irradiance since 1700 from the surface magnetic flux |journal=A&A |volume=467 |issue=1 |pages=335–46 |year=2007 |doi=10.1051/0004-6361:20066725 |url=http://www.aanda.org/articles/aa/abs/2007/19/aa6725-06/aa6725-06.html |bibcode=2007A&A...467..335K}}</ref><ref>{{cite journal |last1=Steinhilber |title=Total solar irradiance during the Holocene |journal=Geophys. Res. Lett. |volume=36 |issue=19 |pages=L19704 |year=2009 |doi=10.1029/2009GL040142 |first1=F. |last2=Beer |first2=J. |last3=Fröhlich |first3=C. |bibcode=2009GeoRL..3619704S}}</ref> | |||
| * Different TSR composite reconstructions of satellite observations show different trends since 1980; see the ''global warming'' section below. | |||
| ===Ultraviolet irradiance=== | |||
| * Ultraviolet irradiance (EUV) varies by approximately 1.5 percent from solar maxima to minima, for 200 to 300 nm UV.<ref>{{cite journal |title=Contribution of Ultraviolet Irradiance Variations to Changes in the Sun's Total Irradiance |volume=244 |issue=4901 |date=14 April 1989 |doi=10.1126/science.244.4901.197 |url=http://www.sciencemag.org/cgi/content/abstract/244/4901/197 |quote=1 percent of the sun's energy is emitted at ultraviolet wavelengths between 200 and 300 nanometers, the decrease in this radiation from 1 July 1981 to 30 June 1985 accounted for 19 percent of the decrease in the total irradiance |last1=Lean |first1=J. |journal=Science |pages=197–200 |pmid=17835351|bibcode = 1989Sci...244..197L }} (19% of the 1/1366 total decrease is 1.4% decrease in UV)</ref> <!-- commented out as dubious and unsourced, please reinsert with UV wavelength ranges and cites: widely through factors of 2 to 10 during a solar cycle. --> | |||
| * Energy changes in the UV wavelengths involved in production and loss of ] have atmospheric effects. | |||
| ** The 30 ] ] level has changed height in phase with solar activity during solar cycles 20-23. | |||
| ** UV irradiance increase causes higher ozone production, leading to stratospheric heating and to poleward displacements in the ] and ] wind systems.<ref>{{cite journal|last=Haigh|first=J D|journal=Science|date=May 17, 1996|volume=272|pages=981–984|doi=10.1126/science.272.5264.981|issue=5264}}</ref> | |||
| * A proxy study estimated that UV has increased by 3.0% since the Maunder Minimum.<ref>{{Cite journal | first1=M.| last1=Fligge | first2=S. K.| last2=Solanki | title=The solar spectral irradiance since 1700 | doi=10.1029/2000GL000067 | journal=Geophysical Research Letters | volume=27 | year=2000 | pages=2157–2160 | url=http://www.mps.mpg.de/dokumente/publikationen/solanki/j111.pdf | format=PDF | accessdate=12 June 2011 | issue=14 | bibcode=2000GeoRL..27.2157F}}</ref> | |||
| ===Solar wind and magnetic flux=== | |||
| * A more active ] and stronger magnetic field reduces the ] striking the Earth's atmosphere.<ref name="National | |||
| Research Council"></ref> | |||
| * Variations affect ] size and intensity the volume larger than the Solar System filled with solar wind particles. | |||
| * Cosmogenic production of <sup>14</sup>C and <sup>36</sup>Cl show changes tied to solar activity. The production rate of <sup>10</sup>Be and TSI over the past millennium is more complicated because of possible climate influence of <sup>10</sup>Be deposition rate, causing errors in the inferred <sup>10</sup>Be formation rate.<ref name="Field, C., Schmidt, G., Koch, D. & Salyk, C. Modeling production and climate- | |||
| related impacts on 10 Be concentration in ice cores. J. Geophys. Res."></ref> | |||
| * ] ] in the upper atmosphere does change, but significant effects are not obvious. | |||
| * As the ]-source magnetic flux doubled during the past century, the cosmic-ray flux decreased by about 15%.{{citation needed|date=June 2012}} | |||
| * 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.{{citation needed|date=June 2012}} | |||
| ===Cosmic ray-clouds claim=== | |||
| Various speculations about cosmic rays include: | |||
| * Tinsley and Yu claimed that changes in ionization affect the aerosol abundance that serves as the condensation nucleus for cloud formation.<ref name="Tinsley2004">{{Cite book | |||
| | contribution=Atmospheric Ionization and Clouds as Links Between Solar Activity and Climate | |||
| | first1=Brian A. | |||
| | last1=Tinsley| first2=Fangqun | |||
| | last2=Yu | |||
| | year=2004 | |||
| | volume=141 | |||
| | pages=321–339 | |||
| | editor1-first=Judit M. | |||
| | editor1-last=Pap | |||
| | editor2-first=Peter | |||
| | editor2-last=Fox | |||
| | title=Solar Variability and its Effects on Climate | |||
| | isbn=0-87590-406-8 | |||
| | contribution-url=http://www.utdallas.edu/physics/pdf/Atmos_060302.pdf | |||
| | accessdate=19 April 2007 | |||
| | publisher=] | |||
| | work=Geophysical monograph series}} | |||
| </ref> During periods of low solar activity (during solar minima), more cosmic rays reach Earth, potentially creating ultra-small aerosol particles as precursors to ].<ref name="CERN Clouds">{{cite pressrelease | title= CERN’s CLOUD experiment provides unprecedented insight into cloud formation | publisher=] | url=http://press.web.cern.ch/press/PressReleases/Releases2011/PR15.11E.html |date=25 August 2011| accessdate=3 November 2011 }}</ref> Clouds formed from greater amounts of condensation nuclei are brighter, longer lived and likely to produce less precipitation. | |||
| * A change in cosmic rays could cause an increase in certain types of clouds, affecting Earth's ]. | |||
| * Several percent variation in cosmic rays and in tropospheric ionization occurs when the interplanetary magnetic field changes over the solar cycle, greater than the typically 0.1% variation in total solar irradiance.<ref name="shaviv2005">{{Cite journal | title=On climate response to changes in the cosmic ray flux and radiative budget | journal=Journal of Geophysical Research | volume=110 | year=2005 | url=http://www.phys.huji.ac.il/~shaviv/articles/sensitivity.pdf | format=PDF | doi=10.1029/2004JA010866 | accessdate=17 June 2011 | author=Shaviv, Nir J | issue=A08105 | bibcode=2005JGRA..11008105S|arxiv = physics/0409123 }}</ref><ref name="Svensmark2007">{{Cite journal | title=Cosmoclimatology: a new theory emerges | journal=Astronomy & Geophysics | volume=48 | year=2007 | pages=1.18–1.24 | doi=10.1111/j.1468-4004.2007.48118.x| author=Svensmark, Henrik | issue=1 | bibcode=2007A&G....48a..18S}}</ref> | |||
| * Particularly at high ]s, with less shielding from Earth's magnetic field, cosmic ray variation may impact terrestrial low altitude cloud cover (unlike a lack of correlation with high altitude clouds), partially influenced by the solar-driven interplanetary magnetic field (as well as passage through the galactic arms over longer timeframes).<ref name="shaviv2005" /><ref name="Svensmark2007" /><ref name="Svensmark1998" /><ref>{{Cite journal | title=Celestial driver of Phanerozoic climate? | journal=Geological Society of America | volume=13 | year=2003 | pages=4 | url=http://www.juniata.edu/projects/oceans/GL111/celestialdriverofclimate.pdf | format=PDF | doi=10.1130/1052-5173(2003)013<0004:CDOPC>2.0.CO;2 | accessdate=17 June 2011 | author=Shaviv, Nir J and Veizer, Ján | issue=7}}</ref> | |||
| Three subsequent papers claimed that production of clouds via cosmic rays could not be explained by nucleation particles. Accelerator results failed to produce sufficient, and sufficiently large, particles to result in cloud formation;<ref>{{Cite journal | author1=Pierce, J. | author2=Adams, P. | title=Can cosmic rays affect cloud condensation nuclei by altering new particle formation rates? | journal=Geophysical Research Letters | volume=36 | issue=9 | page=36 | year=2009 }}</ref><ref>{{Cite journal | author=Snow-Kropla, E. | display-authors=etal | title=Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties | journal=Atmospheric Chemistry and Physics | volume=11 | issue=8 | date=Apr 2011 | page=4001}}</ref> this includes observations after a major solar storm.<ref name="Erlykin, A., et al. 137">{{Cite journal | author=Erlykin, A. | display-authors=etal | title=A review of the relevance of the ‘CLOUD’ results and other recent observations to the possible effect of cosmic rays on the terrestrial climate | journal=Meteorology and Atmospheric Physics | volume=121 | issue=3 | page=137 | date=Aug 2013 }}</ref> Observations after ] do not show any induced clouds.<ref>{{Cite proceedings | author1=Sloan, T.| author2=Wolfendale, A. | title=Cosmic Rays and Global Warming | book-title=30TH INTERNATIONAL COSMIC RAY CONFERENCE, Merida, Mexico | date=Jun 2007 }}</ref> | |||
| A 2002 paper immediately refuted Svensmark's hypothesis.<ref>{{Cite journal | author1=Sun, B., | author2=Bradley, R. | title=Solar influences on cosmic rays and cloud formation: A reassessment | journal=Journal of Geophysical Research | volume=107 | issue=D14 | year=2002 }}</ref> Multiple 2013 papers,<ref name="Erlykin, A., et al. 137" /><ref>{{Cite journal | author=Benestad, R | title=Are there persistent physical atmospheric responses to galactic cosmic rays? | journal=Environmental Research Letters | volume=8 | issue=3 | page= 035049 | date=Sep 2013 }}</ref><ref>{{Cite journal | author1=Sloan, T. | author2=Wolfendale, A. | title=Cosmic rays, solar activity and the climate | journal=Environmental Research Letters | volume=8 | issue=4 | page=045022 | date=Nov 2013 }}</ref><ref>{{Cite journal | author1=Krissansen-Totton, J., | author2=Davies, R. | title=Investigation of cosmic ray–cloud connections using MISR | journal=Geophysical Research Letters | volume=40 | issue=19 | page= 5240 | date=Oct 2013 }}</ref> and a 2015 paper<ref>{{Cite journal | author1=Tsonis, A., | author2=Deyle, E. | display-authors=etal | title=Dynamical evidence for causality between galactic cosmic rays and interannual variation in global temperature | journal=PNAS | volume=112 | issue=11 | date=Mar 2015 }}</ref> could find no correlation between cosmic ray levels and global temperature on the multidecadal timescale of recent warming, as cosmic ray levels do not show a corresponding trend, on multidecadal<ref>{{Cite web | url=http://blog.motheyes.com/2011/09/cosmic-rays/ |access-date=Mar 2015}}</ref><ref>{{Cite web | url=http://climatecrocks.com/2013/11/12/finally-cosmic-ray-theory-of-climate-change-dead/ |access-date=Mar 2015}}</ref><ref>{{Cite web | url=http://skepticalscience.com/cosmic-rays-cosmically-behind-humans-explaining-global-warming.html |access-date=Mar 2015}}</ref><ref>{{Cite web | url=https://cr-game-staging.herokuapp.com/myths/24 |access-date=Mar 2015}}</ref> or longer timescales.<ref>{{Cite journal | author1=Sloan, T. | author2=Wolfendale, A. | title=Cosmic rays and climate change over the past 1000 million years | journal=New Astronomy | volume=25 | issue= | page=45 | date=Dec 2013 }}</ref><ref>{{Cite journal | author1=Feng, F., | author2=Bailer-Jones, C. | title=Assessing the Influence of the Solar Orbit on Terrestrial Biodiversity | journal=Astrophysical Journal | volume=768 | issue=2 | page=152 | year=2013 }}</ref> | |||
| The claim that recent warming is due to cosmic rays is not considered credible.<ref>{{Cite web | url=http://www.grida.no/publications/other/ipcc_tar/?src=/climate/IPCC_tar/wg1/246.htm |access-date=Mar 2015 }}</ref><ref>{{Cite web | url= http://www.dailyclimate.org/tdc-newsroom/2013/11/cosmic-rays |access-date=Mar 2015 }}</ref><ref>{{Cite web | url=http://blog.motheyes.com/2011/09/cosmic-rays/ |access-date=Mar 2015 }}</ref><ref>{{Cite web | author=Kollipara, P. | title=No, cosmic rays aren’t causing global warming | work=Washington Post | date=12 Mar 2015|url=http://www.washingtonpost.com/news/energy-environment/wp/2015/03/12/no-cosmic-rays-arent-causing-global-warming/ }}</ref> | |||
| ==Other variation effects== | |||
| Interaction of solar particles, the solar magnetic field and the Earth's magnetic field cause variations in the particle and electromagnetic fields at the planetary surface. 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. | |||
| ===Geomagnetic effects=== | |||
| ]. Sizes not to scale.]] | |||
| The Earth's ]e are visual displays created by interactions between the ], the ], the Earth's magnetic field and the Earth's atmosphere. Variations in any of these affect aurora displays. Solar ], associated with high solar activity, produce enhanced auroral activity, and visible aurorae at lower than usual latitudes. | |||
| Sudden changes can cause the intense disturbances in the Earth's magnetic fields that are called ]s. | |||
| ===Solar proton events=== | |||
| Energetic ]s can reach Earth within 30 minutes of a major flare's peak. During such a ], 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 significantly increase the radiation environment. | |||
| ===Cosmic rays=== | |||
| {{Main|Cosmic ray}} | |||
| <!-- ] around solar system.]]--> | |||
| {{No footnotes|section|date = July 2015}}An increase in solar activity (more sunspots) is accompanied by an increase in the "]," which is an outflow of ionized particles, mostly protons and electrons, from the sun. The Earth's geomagnetic field, the solar wind and the solar magnetic field deflect ]s (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, ] is a dominant source of ionization in many areas). | |||
| 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 ]. The 80–90-year solar Gleissberg cycles appear to vary in length depending upon the lengths of the concurrent 11-year solar cycles. | |||
| ===Carbon-14 production=== | |||
| ] | |||
| The production of ] (radiocarbon: <sup>14</sup>C) also is related to solar activity. Carbon-14 is produced in the upper atmosphere when cosmic ray bombardment of atmospheric nitrogen (<sup>14</sup>N) induces the Nitrogen to undergo ], thus transforming into an unusual isotope of carbon with an atomic weight of 14 rather than the more common 12. Because cosmic rays are partially excluded from the Solar System by the outward sweep of magnetic fields in the solar wind, increased solar activity results in a reduction of cosmic rays reaching the Earth's atmosphere and thus reduces <sup>14</sup>C production. Thus the cosmic ray intensity and carbon-14 production vary inversely to the general level of solar activity.<ref>{{cite web | |||
| | url= http://users.zoominternet.net/~matto/M.C.A.S/sunspot_cycle.htm | |||
| | title= Astronomy: On the Sunspot Cycle | |||
| | accessdate= 2008-02-27 }}</ref> | |||
| Therefore, the atmospheric <sup>14</sup>C concentration is ''lower'' during sunspot maxima and ''higher'' during sunspot minima. By measuring the captured <sup>14</sup>C 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 <sup>14</sup>C production was much higher during the mid-] 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 ] and by changes in carbon cycling within the ] (particularly those associated with changes in the extent of vegetation since the last ]){{citation needed|date=January 2014}} | |||
| == Solar variation and climate == | |||
| {{See also|Radiative forcing|Climate sensitivity}} | |||
| ] | |||
| Both long-term and short-term variations in solar activity are hypothesized to affect global climate, but it has proven challenging to directly quantify the link.<ref name= "haigh">Joanna D. Haigh "", ''Living Reviews in Solar Physics'' (access date 31 January 2012</ref> | |||
| As discussed above, three mechanisms are proposedby which solar variations affect climate: | |||
| * Solar irradiance changes directly affecting the climate ("]"). This is generally considered to be a minor effect, as the amplitudes of the variations in solar irradiance are too small to have significant effect absent some amplification process.<ref name="UCARbrightness" /> | |||
| * Variations in the ultraviolet component. The UV component varies by more than the total, so if UV were for some (as yet unknown) reason to have a disproportionate effect, this might explain a larger solar signal. | |||
| * Effects mediated by changes in cosmic rays (which are affected by the solar wind) such as changes in cloud cover. | |||
| Early research attempted to find a correlation between weather and sunspot activity, mostly without notable success.<ref name="Weart" /><ref name="frits" /> Later research has concentrated more on correlating solar activity with global temperature. | |||
| ] | |||
| Crucial to the understanding of possible solar impact on terrestrial climate is accurate measurement of solar forcing. Unfortunately accurate measurement of incident solar radiation is only available since the satellite era, and even that is open to dispute: different groups find different values, due to different methods of cross-calibrating measurements taken by instruments with different spectral sensitivity. Scafetta and Willson found significant variations of solar luminosity between 1980 and 2000.<ref>{{cite journal |first1=Nicola |last1=Scafetta |first2=Richard |last2=Willson |title=ACRIM-gap and Total Solar Irradiance (TSI) trend issue resolved using a surface magnetic flux TSI proxy model |journal=Geophysical Research Letter |volume=36 |pages=L05701 |year=2009 |doi=10.1029/2008GL036307 |bibcode=2009GeoRL..3605701S |issue=5}}</ref> But Lockwood and Frohlich<ref>{{cite journal |first1=Mike |last1=Lockwood |first2=Claus |last2=Fröhlich |title=Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature. II. Different reconstructions of the total solar irradiance variation and dependence on response time scale |journal=Proceedings of the Royal Society A |volume=464 |issue=2094 |pages=1367–85 |date=8 June 2008 |doi=10.1098/rspa.2007.0347 |url=http://rspa.royalsocietypublishing.org/content/464/2094/1367.abstract |bibcode=2008RSPSA.464.1367L}}</ref> find that solar forcing has declined since 1987. | |||
| The ] (IPCC) ] (TAR) concluded that the measured magnitude of recent solar variation is much smaller than the amplification effect due to greenhouse gases, but acknowledged that scientific understanding is poor with respect to solar variation.<ref>{{AR4|WG1|chapter=2|section=2.9.1 Uncertainties in Radiative Forcing | section-url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-9-1.html#table-2-11 }}</ref><ref name="grida fig6-6">{{Cite book | editor1-first=J.T. | editor1-last=Houghton | editor1-link=John T. Houghton | editor2-first=Y. | editor2-last=Ding | editor3-first=D.J. | editor3-last=Griggs | editor4-first=M. | editor4-last=Noguer | displayeditors = 3| title=Climate Change 2001: Working Group I: The Scientific Basis | url=http://www.grida.no/climate/ipcc_tar/wg1/index.htm | year=2001 | publisher=] | |||
| | chapter=6.11 Total Solar Irradiance—Figure 6.6: Global, annual mean radiative forcings (1750 to present) | |||
| | chapter-url=http://www.grida.no/climate/ipcc_tar/wg1/fig6-6.htm | accessdate=15 April 2007 }}</ref> | |||
| Estimates of long-term solar irradiance changes have decreased since the TAR. However, empirical results of detectable tropospheric changes have strengthened the evidence for solar forcing of climate change. The most likely mechanism is considered to be some combination of direct forcing by TSR changes and indirect effects of ultraviolet (UV) radiation on the stratosphere. Least certain are indirect effects induced by cosmic rays.<ref></ref> | |||
| In 2002, Lean ''et al''.<ref name="www.agu.org.99">{{Cite journal | first1=J.L. | last1=Lean | first2=Y.-M | last2=Wang | first3=N.R | last3=Sheeley Jr. | title=The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate | year=2002 | pages=77–1~77–4 | volume=29 | issue=24 | journal=] | doi=10.1029/2002GL015880 | url=http://www.agu.org/pubs/crossref/2002.../2002GL015880.shtml | bibcode=2002GeoRL..29x..77L}}</ref> stated that while "There is ... growing empirical evidence for the Sun's role in ] on multiple time scales including the 11-year cycle", "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 ... because the stochastic response increases with the cycle amplitude, not because there is an actual secular irradiance change." They conclude that because of this, "long-term climate change may appear to track the amplitude of the solar activity cycles," but that "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 suggests that ] simulations of twentieth century warming may overestimate the role of solar irradiance variability." More recently, a study and review of existing literature published in ] in September 2006 suggests that the evidence is solidly on the side of solar brightness having relatively little effect on global climate, with little likelihood of significant shifts in solar output over long periods of time.<ref name="UCARbrightness"/><ref>{{Cite journal | first1=P. | last1=Foukal | first2=C. | last2=Fröhlich | first3=H. | last3=Spruit | first4=T. M. L. | last4=Wigley | title=Variations in solar luminosity and their effect on the Earth's climate | url=http://www.mpa-garching.mpg.de/mpa/publications/preprints/pp2006/MPA2001.pdf |format=PDF| doi=10.1038/nature05072 | journal=] | pmid=16971941 | volume=443 | issue=7108 | year=2006 | pages=161–6 | bibcode=2006Natur.443..161F}}</ref> Lockwood and Fröhlich, 2007, find that there "is considerable evidence for solar influence on the Earth's pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century," but that "over the past 20 years, all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures."<ref>{{cite journal | |||
| | last = Lockwood | |||
| | first = Mike | |||
| |author2=Claus Fröhlich | |||
| | title = Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature | |||
| | journal = Proceedings of the Royal Society A | |||
| | volume =463 | |||
| | pages = 2447 | |||
| | quote = Our results show that the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanisms is invoked and no matter how much the solar variation is amplified. | |||
| | url = http://www.atmos.washington.edu/2009Q1/111/Readings/Lockwood2007_Recent_oppositely_directed_trends.pdf | |||
| | doi = 10.1098/rspa.2007.1880 | |||
| |format=PDF | |||
| | year = 2007 | |||
| | bibcode=2007RSPSA.463.2447L | |||
| | issue = 2086}}</ref> In a study that brought geomagnetic activity into the discussion, as a measure of known solar-terrestrial interaction, Love et al. found a statistically significant correlation between sunspots and geomagnetic activity, but they found no statistically significant correlation between global surface temperature and either sunspot number or geomagnetic activity.<ref>{{cite journal|author=Love, J. J.|author2=Mursula, K. |author3=Tsai, V. C. |author4=Perkins, D. M. |year= 2013|title= Are secular correlations between sunspots, geomagnetic activity, and global temperature significant?|journal= Geophysical Research Letters|volume=38|doi=10.1029/2011GL049380 |bibcode=2011GeoRL..3821703L}}</ref> | |||
| Benestad and Schmidt<ref>{{cite journal | |||
| | last = Benestad, | |||
| | first = R. E. | |||
| |author2=G. A. Schmidt | |||
| | title = Solar trends and global warming | |||
| | journal = Journal of Geophysical Research – Atmospheres | |||
| | volume = 114 | |||
| | date = 21 July 2009 | |||
| | quote = the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th century and is negligible for warming since 1980. | |||
| | url = http://pubs.giss.nasa.gov/docs/2009/2009_Benestad_Schmidt.pdf | |||
| | doi = 10.1029/2008JD011639 | |||
| | bibcode=2009JGRD..11414101B | |||
| }}</ref> concluded that "the most likely contribution from solar forcing a global warming is 7 ± 1% for the 20th century and is negligible for warming since 1980." This paper disagrees with Scafetta and West,<ref name=Scafetta07/> who claimed that solar variability has a significant effect on climate forcing. Based on correlations between specific climate and solar forcing reconstructions, they argue that a "realistic climate scenario is the one described by a large preindustrial secular variability (''e.g.'', the paleoclimate temperature reconstruction by Moberg et al.)<ref>{{cite journal |last1=Moberg |title=Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data |journal=Nature |volume=433 |pages=613–7 |url=http://www.ncdc.noaa.gov/paleo/pubs/moberg2005/moberg2005.html |doi=10.1038/nature03265 |pmid=15703742 |year=2005 |first1=A |last2=Sonechkin |first2=DM |last3=Holmgren |first3=K |last4=Datsenko |first4=NM |last5=Karlén |first5=W |last6=Lauritzen |first6=SE |issue=7026 |bibcode=2005Natur.433..613M}}</ref> with TSR experiencing low secular variability (as the one shown by Wang et al.).<ref>{{Cite journal |title=Modeling the Sun's Magnetic Field and Irradiance since 1713 |journal=The Astrophysical Journal |volume=625 |pages=522–38 |date= May 2005|doi=10.1086/429689 |url=http://www.journals.uchicago.edu/doi/full/10.1086/429689 |last1=Wang |first1=Y.‐M. |last2=Lean |first2=J. L. |last3=Sheeley |first3=N. R. |bibcode=2005ApJ...625..522W}})</ref> Under this scenario, according to Scafetta and West, the Sun might have contributed 50% of the observed global warming since 1900.<ref name=Scafetta06>{{cite journal |last1=Scafetta |first1=N. |first2=B. J. |last2=West |title=Phenomenological solar signature in 400 years of reconstructed Northern Hemisphere temperature record |journal=Geophys. Res. Lett. |volume=33 |pages=L17718 |year=2006 |doi=10.1029/2006GL027142 |url=http://www.agu.org/journals/gl/gl0617/2006GL027142/ |bibcode=2006GeoRL..3317718S |issue=17}}</ref> Stott ''et al.'' estimate that the residual effects of the prolonged high solar activity during the last 30 years account for between 16% and 36% of warming from 1950 to 1999.<ref name="Stott2003">{{Cite journal| title=Do Models Underestimate the Solar Contribution to Recent Climate Change| first=Peter A.| last=Stott| author2= Gareth S. Jones | author3= John F. B. Mitchell| journal=Journal of ClimateDecember|year=2003| volume=16| pages=4079–4093 | url=http://climate.envsci.rutgers.edu/pdf/StottEtAl.pdf | accessdate=5 October 2005 | doi = 10.1175/1520-0442(2003)016<4079:DMUTSC>2.0.CO;2 |bibcode = 2003JCli...16.4079S| issue=24 }}</ref> | |||
| ===Effect on global warming=== | |||
| Recent rises in Earth average temperature cannot be explained by solar radiative forcing as its primary cause. This has been deduced via ] lines of evidence: | |||
| ====Direct measurement and time series==== | |||
| Neither direct measurements nor proxies of solar variation correlate well with Earth global temperature,<ref>{{ cite journal | first=A. | last=Schurer | display-authors=etal | title=Small influence of solar variability on climate over the past millennium |date=December 2013 | pages=104–108 | volume=7 | journal=Nature Geoscience | doi=10.1038/ngeo2040}}</ref> particularly in recent decades.<ref>{{cite journal | first=L. | last=Lockwood | first2=C. | last2=Fröhlich | title=Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature |date=October 2007 | pages=2447–2460 | volume=463 | issue=2086 | journal=Proceedings of the Royal Society A | doi=10.1098/rspa.2007.1880 | bibcode=2007RSPSA.463.2447L}}</ref><ref>{{cite journal | first=P. | last=Foukal | display-authors=etal | title=Variations in solar luminosity and their effect on the Earth's climate |date=September 2006 | pages=161–166 | volume=443 | journal=Nature | doi=10.1038/nature05072 | pmid=16971941 | issue=7108}}</ref> | |||
| ====Diurnal criterion==== | |||
| Globally, average diurnal temperature range has decreased.<ref>{{cite journal | first=Thomas | last=Karl | display-authors=etal | title=A New Perspective on Recent Global Warming: Asymmetric Trends of Daily Maximum and Minimum Temperature | year=1993 | pages=1007–1023 | volume=74 | journal=Bulletin of the American Meteorological Society | doi=10.1175/1520-0477(1993)074<1007:anporg>2.0.co;2}}</ref><ref>{{cite journal | first=K | last=Braganza | display-authors=etal | title=Diurnal temperature range as an index of global climate change during the twentieth century |date=July 2004 | volume=31 | issue=13 | journal=Geophysical Research Letters | doi = 10.1029/2004gl019998 | bibcode=2004GeoRL..3113217B}}</ref><ref>{{cite journal | first=L. | last=Zhou | display-authors=etal | title=Detection and attribution of anthropogenic forcing to diurnal temperature range changes from 1950 to 1999: comparing multi-model simulations with observations |date=August 2009 | pages=1289–1307 | volume=35 | journal=Climate Dynamics | doi=10.1007/s00382-009-0644-2}}</ref> That is, daytime temperatures have not risen as fast as nighttime temperatures have warmed. This is the opposite of the expected warming if solar energy (falling primarily or wholly on Earth's dayside, depending on energy regime) were the principal means of forcing. It is, however, the ] if greenhouse gases were preventing radiative escape, which is more prevalent on Earth's nightside.<ref>{{cite journal | first=S. | last=Peng | display-authors=etal | title=Rice yields decline with higher night temperature from global warming |date=June 2004 | pages=9971–9975 | volume=35 | issue=27 | journal=Proceeding of the National Academy of Sciences }}</ref> | |||
| ====Hemispheric and latitudinal criteria==== | |||
| The Northern Hemisphere is warming faster than the Southern Hemisphere.<ref>{{ cite journal | first=A. | last=Armstrong | title=Northern warming | volume=6 |date=February 2013 | journal=Nature Geoscience | doi=10.1038/ngeo1763 }}</ref><ref>{{ cite web | url=http://cdiac.ornl.gov/trends/temp/jonescru/jones.html | accessdate=17 Oct 2014 }}</ref> This is the opposite of the expected pattern if the Sun, currently ] to the Earth ], were the principal climate forcing. In particular, the Southern Hemisphere, with more ocean area and less land area, has a lower ] and absorbs more light. The Northern Hemisphere, however, has a higher population, industry, and emissions.{{Citation needed|date = July 2015}} | |||
| Furthermore, the Arctic region is not only warming faster than the Antarctic, but faster than northern mid-latitudes and subtropics, despite polar regions receiving ] than lower latitudes.{{Citation needed|date = July 2015}} | |||
| ====Altitude criterion==== | |||
| Solar forcing should warm Earth's atmosphere roughly evenly by altitude, with some variation by wavelength/energy regime. However, the atmosphere is warming at lower altitudes, and actually cooling at higher altitudes. This is the expected pattern if greenhouse gases are driving temperature,<ref>{{ cite journal | first= H. | last=Lewis | display-authors=etal | title=Response of the Space Debris Environment to Greenhouse Cooling |date=April 2005 | page=243 | journal=Proceedings of the 4th European Conference on Space Debris }}</ref><ref>{{cite web | url=http://arstechnica.com/science/2008/02/unpacking-interplay-of-solar-variability-and-climate-change/ | accessdate=17 Oct 2014}}</ref> as ].<ref>{{cite journal | first=J. | last=Picone | first2=J. | last2=Lean | display-authors=etal | title=Global Change in the Thermosphere: Compelling Evidence of a Secular Decrease in Density | year=2005 | pages=225–227 | journal=2005 NRL Review}}</ref> | |||
| ===Solar variation theory=== | |||
| A 1994 U.S. ] study concluded that TSI variations were the most likely cause of significant climate change in the pre-industrial era, before significant human-generated carbon dioxide entered the atmosphere.<ref name="books.nap.edu"/> | |||
| Scafetta and West correlated solar proxy data and lower ] temperature for the preindustrial era, before significant anthropogenic greenhouse forcing, suggesting that TSI variations may have contributed to 50% of the global warming observed between 1900 and 2000 (although they conclude "our estimates about the solar effect on climate might be overestimated and should be considered as an upper limit.")<ref name=Scafetta07>{{cite journal |last1=Scafetta |first1=N. |first2=B. J. |last2=West |title=Phenomenological reconstructions of the solar signature in the Northern Hemisphere, surface temperature records since 1600 |journal=J. Geophys. Res. |volume=112 |pages=D24S03 |year=2007 |doi=10.1029/2007JD008437 |url=http://www.agu.org/pubs/crossref/2007/2007JD008437.shtml |bibcode=2007JGRD..11224S03S}} (access date 2012-1-31)</ref> This contrasts with the results from GCMs that predict solar forcing of climate through direct ] is too small to explain a significant contribution.<ref>{{cite journal |last1=Hansen |first1=J |title=Efficacy of climate forcings |journal=J. Geophys. Res. |volume=110 |pages=D18104 |year=2005 |doi=10.1029/2005JD005776 |bibcode=2005JGRD..11018104H}}</ref> The relative significance of solar variability and other forcings of climate change during the industrial era is an area of ongoing research. | |||
| ] | |||
| In 2000, Stott and others<ref name="Stott2000">{{cite journal | author=Stott, Peter A. | display-authors=etal | title=External Control of 20th Century Temperature by Natural and Anthropogenic Forcings | journal=Science | year=2000 | volume=290 |pages=2133–7 | doi=10.1126/science.290.5499.2133 | pmid=11118145 | issue=5499 |bibcode = 2000Sci...290.2133S }}</ref> reported on the most comprehensive model simulations of 20th century climate to that date. 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 group found that combining 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" but not indirect effects mediated through cosmic rays.<ref name="www.sciencemag.org.108">{{Cite journal | first1=K.S. | last1=Carslaw | first2=R. G. | last2=Harrison | first3=J. | last3=Kirkby | title=Cosmic Rays, Clouds, and Climate | journal=] | volume=298 | pages=1732–7 | year=2002 | doi=10.1126/science.1076964 | url=http://www.seas.harvard.edu/climate/pdf/carslaw-2002.pdf |format=PDF| accessdate=18 April 2007 | pmid=12459578 | issue=5599 |bibcode = 2002Sci...298.1732C }} | |||
| </ref> 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.<ref name="Stott2000" /> A graphical representation<ref name="www.grida.no.110">{{cite web | title=graphical representation | url=http://www.grida.no/climate/ipcc_tar/wg1/fig12-7.htm | accessdate = 2005-10-05}}</ref> of the relationship between natural and anthropogenic factors contributing to climate change appears in "Climate Change 2001: The Scientific Basis", a report by the ] (IPCC).<ref name="www.grida.no.111">{{cite web | title=Climate Change 2001: The Scientific Basis | url=http://www.grida.no/climate/ipcc_tar/wg1/index.htm | accessdate = 2005-10-05}}</ref> | |||
| Stott's 2003 work largely revised his assessment, and found a significant solar contribution to recent warming, although still smaller (between 16 and 36%) than that of greenhouse gases.<ref name="Stott2003">{{Cite journal | first1=Peter A. | last1=Stott | first2=Gareth S. | last2=Jones | first3=John F. B. | last3=Mitchell | title=Do Models Underestimate the Solar Contribution to Recent Climate Change? | year=2003 | journal=] | volume=16 | issue=24 |pages=4079–93 | doi=10.1175/1520-0442(2003)016<4079:DMUTSC>2.0.CO;2 | accessdate=16 April 2007 | format=PDF | url=http://climate.envsci.rutgers.edu/pdf/StottEtAl.pdf |bibcode = 2003JCli...16.4079S }}</ref> | |||
| ], the director of the ] in ], Germany said: | |||
| <blockquote>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.<ref name="washtimes2004">{{cite news | first=Michael | last=Leidig | publisher=] | date=18 July 2004 | accessdate=2007-04-18 | title=Hotter-burning sun warming the planet | url=http://www.washtimes.com/world/20040718-115714-6334r.htm }}</ref></blockquote> | |||
| Nevertheless, Solanki agrees with the ] that the marked upswing in temperatures since about 1980 is attributable to human activity. | |||
| <blockquote>"Just how large this role 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."<ref name="www.mpg.de/english/">{{cite pressrelease | title=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 | publisher=] | date=2 August 2004 | accessdate=2007-04-16 | url=http://www.mpg.de/english/illustrationsDocumentation/documentation/pressReleases/2004/pressRelease20040802/ }}</ref></blockquote> | |||
| ===Little Ice Age=== | |||
| {{Main|Little Ice Age}} | |||
| One historical long-term correlation between solar activity and climate change is the 1645–1715 Maunder minimum, a period of little or no sunspot activity which partially overlapped the "]" during which cold weather prevailed in Europe. The Little Ice Age encompassed roughly the 16th to the 19th centuries<ref name= "Lamb1972">H. H. Lamb, "The cold Little Ice Age climate of about 1550 to 1800," in ''Climate: present, past and future,'' London: Methuen. p. 107 (1972). ISBN 0-416-11530-6</ref><ref name="Emmanuel1971">{{cite book |author=Emmanuel Le Roy Ladurie |title=Times of Feast, Times of Famine: a History of Climate Since the Year 1000 |publisher=Doubleday |location=Garden City, NY |year=1971 |oclc=164590 |others=Barbara Bray |isbn= 0-374-52122-0}}</ref><ref></ref> It is debated whether the low solar activity caused the cooling, or whether the cooling was caused by other factors. | |||
| The Spörer Minimum was linked to a significant cooling period between 1460 and 1550.<ref name="Geoffrey1997">{{cite book|title=The general crisis of the seventeenth century|url=http://books.google.com/?id=HGLs23umDXAC&pg=PA287&dq=Sp%C3%B6rer+Minimum+little+ice+age&cd=4#v=onepage&q=|author=Geoffrey Parker, Lesley M. Smith|publisher=]|pages=287, 288|isbn=978-0-415-16518-1|year=1997}}</ref> Other indicators of low solar activity during this period are levels of the ] ] and ].<ref name="Crowley2000">{{Cite journal |last=Crowley |first=Thomas J. |journal=] |date=14 July 2000 |volume=289 |issue=5477 |pages=270–7 |title=Causes of Climate Change Over the Past 1000 Years |url=http://www.sciencemag.org/cgi/content/abstract/289/5477/270 |pmid=10894770 |doi=10.1126/science.289.5477.270|bibcode = 2000Sci...289..270C }}</ref> | |||
| A 2012 paper linked the Little Ice Age to an "unusual 50-year-long episode with four large sulfur-rich explosive eruptions," and claimed "large changes in solar irradiance are not required" to explain the phenomenon.<ref name="miller2012">Miller ''et al''. 2012. "Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks" ''Geophysical Research Letters'' '''39''', 31 January: (accessed 31 January 2011)</ref> | |||
| A 2010 paper suggested that a new 90-year period of low solar activity would reduce global average temperatures by about 0.3 °C, which would not be enough to offset the forecasted average global temperature increase due to increased forcing from rising levels of greenhouse gases.<ref>{{cite news|url=http://www.newscientist.com/article/mg20527494.700-a-quiet-sun-wont-save-us-from-global-warming.html|title=A quiet sun won't save us from global warming|date=26 February 2010|work=]|accessdate=7 June 2011}}</ref> | |||
| ===Correlations to solar cycle length=== | |||
| In 1991, Friis-Christensen and Lassen claimed a strong correlation of the length of the solar cycle with temperature changes throughout the northern hemisphere.<ref name="Friis">{{cite journal |first1=E. |last1=Friis-Christensen |first2=K. |last2=Lassen |title=Length of the Solar Cycle: An Indicator of Solar Activity Closely Associated with Climate |journal=Science |volume=254 |issue=5032 |pages=698–700 |date=1 November 1991 |doi=10.1126/science.254.5032.698 |url=http://www.sciencemag.org/content/254/5032/698.abstract |pmid=17774798|bibcode = 1991Sci...254..698F }} </ref> Initially, they used sunspot and temperature measurements from 1861 to 1989 and later extended the period using climate records dating back four centuries. They reported that the relationship appeared to account for nearly 80 per cent of the measured temperature changes over this period. | |||
| The mechanism behind these correlations is a matter of speculation. Laut's 2003 paper<ref>{{Cite journal |last=Laut |first=Peter |title=Solar activity and terrestrial climate: an analysis of some purported correlations |journal=J Atmos Sol Terr Phys |volume=65 |issue=7 |pages=801–12 |date= May 2003|doi=10.1016/S1364-6826(03)00041-5 |bibcode = 2003JASTP..65..801L }}</ref> identified problems with some of these correlation analyses. Damon and Laut claimed<ref name="DamonLaut2004">{{Cite journal | title=Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate Data | url=http://stephenschneider.stanford.edu/Publications/PDF_Papers/DamonLaut2004.pdf | accessdate=5 October 2005| journal=Eos, Transactions, American Geophysical Union| volume=85| issue=39|date=September 28, 2004| pages=370–4| first=Paul E.| last=Damon|author2=Paul Laut | doi=10.1029/2004EO390005|format=PDF | bibcode=2004EOSTr..85..370D}}; see also discussion and references at </ref> that | |||
| <blockquote>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.</blockquote> | |||
| Damon and Laut stated that when the graphs are corrected for filtering errors, the sensational agreement with the recent global warming, which drew worldwide attention, totally disappeared.<ref name="DamonLaut2004"/> | |||
| In 2000, Lassen and ] updated Friis-Christensen and Lassen's 1991 research (which originally only went to 1989) and concluded that while the solar cycle accounted for about half the temperature rise since 1900, it failed to explain a rise of 0.4 °C since 1980.<ref name="archive.newscientist.com.107">{{cite journal | first=Robert | last=Adler | title=Don't blame the Sun | publisher=] | issue=2237 | url=http://www.newscientist.com/article.ns?id=mg16622370.800 | date=6 May 2000 | accessdate=2007-04-19}}</ref> A 2005 review by Benestad<ref>{{cite journal |first=R.E. |last=Benestad |title=A review of the solar cycle length estimates |journal=Geophys. Res. Let. |volume=32 |issue= 15|pages=L15714 |date=13 August 2005 |doi=10.1029/2005GL023621 |url=http://www.agu.org/pubs/crossref/2005.../2005GL023621.shtml|bibcode = 2005GeoRL..3215714B }}</ref> found that the solar cycle did not follow Earth's global mean surface temperature. | |||
| ===Solar variation and weather=== | |||
| There are some suggestions that there may also be regional climate impacts due to the solar activity, such as for the rivers ]<ref>Pablo J.D. Mauas & Andrea P. Buccino. "" page 5. Journal of Atmospheric and Solar-Terrestrial Physics on Space Climate, March 2010. Accessed: 20 September 2014.</ref> and ].<ref>D. Zanchettin, A. Rubino, P. Traverso, and M. Tomasino. "" JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D12102, doi:10.1029/2007JD009157, 19 June 2008. Accessed: 20 September 2014.</ref> Measurements from NASA's ] show that solar UV output is more variable than the total solar irradiance. Climate modelling suggests that low solar activity may result in, for example, colder winters in the US and northern Europe and milder winters in Canada and southern Europe, with little change in globally averaged temperature.<ref name="SolarForcing" /> More broadly, links have been suggested between solar cycles, global climate and events like ].<ref></ref> In other research, Daniel J. Hancock and Douglas N. Yarger found "statistically significant relationships between the double sunspot cycle and the 'January thaw' phenomenon along the East Coast and between the double sunspot cycle and 'drought' (June temperature and precipitation) in the Midwest."<ref>{{cite journal |author=Hancock DJ, Yarger DN |title=Cross-Spectral Analysis of Sunspots and Monthly Mean Temperature and Precipitation for the Contiguous United States |journal=Journal of the Atmospheric Sciences |volume=36 |issue=4 |pages=746–753 |year=1979 |doi=10.1175/1520-0469(1979)036<0746:CSAOSA>2.0.CO;2 |url=http://www.solarstorms.org/USPrecip.html |issn=1520-0469|bibcode = 1979JAtS...36..746H }}</ref> | |||
| Recent research at CERN's ] facility examined links between ] and ], demonstrating the effect of high-energy particulate radiation in nucleating aerosol particles which are precursors to ].<ref name="CERN Clouds" /> Dr. Jasper Kirby, a team leader at CLOUD, said, "At the moment, it actually says nothing about a possible cosmic-ray effect on clouds and climate, but it's a very important first step."<ref name="Cosmic Clouds">{{cite pressrelease | title=Cloud formation may be linked to cosmic rays | publisher=] | url=http://www.nature.com/news/2011/110824/full/news.2011.504.html |date=24 August 2011| accessdate=19 October 2011 }}</ref><ref name="Cosmic Cloud Article">{{cite journal| title=Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation |journal=Nature | url=http://www.nature.com/nature/journal/v476/n7361/full/nature10343.html |date=25 August 2011 |author=Kirkby J |volume=476 |issue=7361 |pages=429–433 |doi=10.1038/nature10343| author2=Curtius J| author3=Almeida J| author4=Dunne E| author5=Duplissy J| display-authors=5| last6=Ehrhart| first6=Sebastian| last7=Franchin| first7=Alessandro| last8=Gagné| first8=Stéphanie| last9=Ickes| first9=Luisa| pmid=21866156 |bibcode = 2011Natur.476..429K }}</ref> | |||
| 1983–1994 data from the ] (ISCCP) showed that global low cloud formation was highly correlated with galactic cosmic ray (GCR) flux; subsequent to this period, the correlation breaks down.<ref name="DamonLaut2004">{{Cite journal | title=Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate Data | url=http://stephenschneider.stanford.edu/Publications/PDF_Papers/DamonLaut2004.pdf | accessdate=5 October 2005| journal=Eos, Transactions, American Geophysical Union| volume=85| issue=39September|date= 28 2004| pages=370–4| first=Paul E.| last=Damon|author2=Paul Laut | doi=10.1029/2004EO390005|format=PDF | bibcode=2004EOSTr..85..370D}}</ref> Changes of 3–4% in cloudiness and concurrent changes in cloud top temperatures have been correlated to the 11 and 22-year ], with increased GCR levels during "antiparallel" cycles.<ref name="Svensmark1998">{{Cite journal | first=Henrik | last=Svensmark | author-link=Henrik Svensmark | title=Influence of Cosmic Rays on Earth's Climate | journal=] | year=1998 | volume=81 | issue=22 | pages=5027–5030 | url=http://www.cosis.net/abstracts/COSPAR02/00975/COSPAR02-A-00975.pdf |format=PDF| doi=10.1103/PhysRevLett.81.5027 | accessdate=17 June 2011 | bibcode=1998PhRvL..81.5027S}}</ref> | |||
| 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.<ref name="Tinsley2004"/> 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.<ref name="Palle2004">{{cite journal | author=E. Pallé, C.J. Butler, K. O'Brien | title=The possible connection between ionization in the atmosphere by cosmic rays and low level clouds | journal=Journal of Atmospheric and Solar-Terrestrial Physics | volume=66 | issue=18 | year=2004 | doi=10.1016/j.jastp.2004.07.041 | url=http://www.arm.ac.uk/preprints/433.pdf |format=PDF | pages=1779|bibcode = 2004JASTP..66.1779P }}</ref><ref name="Palle2005">{{Cite journal | first1=E. | last1=Pallé | title=Possible satellite perspective effects on the reported correlations between solar activity and clouds | journal=] | volume=32 | issue=3| year=2005 | pages=L03802.1–4| doi=10.1029/2004GL021167 | url=http://bbso.njit.edu/Research/EarthShine/literature/Palle_2005_GRL.pdf | format=PDF | bibcode=2005GeoRL..3203802P}}</ref> Difficulties in interpreting such correlations include the fact that many aspects of solar variability change at similar times, and some climate systems have delayed responses. | |||
| === Historical perspective === | |||
| Physicist and historian ] in ''The Discovery of Global Warming'' (2003) writes: | |||
| {{quotation|The study of cycles was generally popular through the first half of the century. Governments had collected a lot of weather data to play with and inevitably people found correlations between sun spot cycles and select weather patterns. If rainfall in England didn't fit the cycle, maybe storminess in New England would. Respected scientists and enthusiastic amateurs insisted they had found patterns reliable enough to make predictions. Sooner or later though every prediction failed. An example was a highly credible forecast of a dry spell in Africa during the sunspot minimum of the early 1930s. When the period turned out to be wet, a meteorologist later recalled "the subject of sunspots and weather relationships fell into dispute, especially among British meteorologists who witnessed the discomfiture of some of their most respected superiors." Even in the 1960s he said, "For a young researcher to entertain any statement of sun-weather relationships was to brand oneself a crank."<ref name="Weart" />}} | |||
| ==See also== | |||
| {{col-begin}} | |||
| {{col-break}} | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| {{col-break}} | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| {{col-break}} | |||
| * ] | |||
| {{col-end}} | |||
| ==References==<!-- Advances in Space Research 37 (2006) 1629–1634 --> | |||
| ===Footnotes=== | |||
| {{Reflist}} | |||
| * {{note|www.grida.no.95}} {{cite web | title=Climate Change 2001: The Scientific Basis | url=http://www.grida.no/climate/ipcc_tar/wg1/122.htm | accessdate = 2005-10-05}} | |||
| * {{note|www.envirotruth.org.94}} {{Cite journal | first=Nir J. | last=Shaviv | author1-link=Nir Shaviv | first2=Ján | last2=Veizer | author2-link=Jan Veizer | title=Celestial driver of Phanerozoic climate? | volume=13 | issue=7 | year=2003 | pages=4–10 | journal=] Today | url=http://www.gsajournals.org/archive/1052-5173/13/7/pdf/i1052-5173-13-7-4.pdf |format=PDF| doi=10.1130/1052-5173(2003)013<0004:CDOPC>2.0.CO;2 | accessdate=19 April 2007 | issn=1052-5173 }} | |||
| * {{note|www.soest.hawaii.edu.96}} {{cite web | title=http://www.soest.hawaii.edu/GG/FACULTY/POPP/Rahmstorf%20et%20al.%202004%20EOS.pdf | url=http://www.soest.hawaii.edu/GG/FACULTY/POPP/Rahmstorf%20et%20al.%202004%20EOS.pdf | accessdate = 2005-10-05|format=PDF}} | |||
| ===General references=== | |||
| *{{Cite journal |last=Abbot |first=C. G. |year=1966 |title=Solar Variation, A Weather Element |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=56 |pmid=16591394 |issue=6 |pages=1627–34 |pmc=220145 |url=http://www.pnas.org/cgi/reprint/56/6/1627.pdf |doi=10.1073/pnas.56.6.1627 |format=PDF|bibcode = 1966PNAS...56.1627A }} | |||
| *{{Cite journal |last=Willson |first=Richard C.|author2=H.S. Hudson|year=1991 |title=The Sun's luminosity over a complete solar cycle |journal=Nature |volume=351 |issue=6321 |pages=42–4 | doi=10.1038/351042a0 |url=http://www.nature.com/nature/journal/v351/n6321/abs/351042a0.html |ref=harv |bibcode=1991Natur.351...42W}} | |||
| *{{Cite web | title=The Sun and Climate | work=U.S. Geological Survey Fact Sheet 0095-00 | url=http://pubs.usgs.gov/fs/fs-0095-00/ | accessdate = 2005-02-21}} | |||
| *{{Cite web | title=The Sun's role in Climate Changes | work=Proc. of The International Conference on Global Warming and The Next Ice Age, 19–24 August 2001, Halifax, Nova Scotia. | url=http://zeus.nascom.nasa.gov/~pbrekke/articles/halifax_brekke.pdf | accessdate = 2005-02-21|format=PDF |archiveurl = http://web.archive.org/web/20041022012450/http://zeus.nascom.nasa.gov/~pbrekke/articles/halifax_brekke.pdf |archivedate = 22 October 2004}} | |||
| *{{Cite journal |last=White |first=Warren B. |author2=Lean, Judith |author3=Cayan, Daniel R. |author4= Dettinger, Michael D. |year=1997 |title=Response of global upper ocean temperature to changing solar irradiance |journal=] |volume=102 |issue=C2 |pages=3255–66 |doi=10.1029/96JC03549 |bibcode=1997JGR...102.3255W}} | |||
| *{{Cite journal |last=Foukal |first=Peter |display-authors=etal |year=1977 |title=The effects of sunspots and faculae on the solar constant |journal=Astrophysical Journal |volume=215 |pages=952 |doi=10.1086/155431 |bibcode=1977ApJ...215..952F}} | |||
| *{{Cite journal |last=Dziembowski |first=W.A. | author2= P.R. Goode| author3= J. Schou |year=2001 |title=Does the sun shrink with increasing magnetic activity? |journal=Astrophysical Journal |volume=553 |issue=2 |pages=897–904 |doi=10.1086/320976 |bibcode=2001ApJ...553..897D|arxiv = astro-ph/0101473 }} | |||
| *{{Cite book |author=Stetson, H.T. |title=Sunspots and Their Effects |publisher=McGraw Hill |location=New York |year=1937 }} | |||
| *{{Cite book |author=Yaskell, S.H., (based upon the work of distinguished solar scientist Cornelis de Jager) |title=Grand Phases On The Sun:the case for a mechanism responsible for extended solar minima and maxima|publisher=Trafford |location=New Jersey |year=2013 }}http://www.prweb.com/releases/StevenHaywoodYaskell/GrandPhasesOnTheSun/prweb11187693.htm | |||
| ==External links== | |||
| *{{Cite journal |author=Gerrit Lohmann, Norel Rimbu, Mihai Dima |title=Climate signature of solar irradiance variations: analysis of long-term instrumental, historical, and proxy data |journal=International Journal of Climatology |volume=24 |issue=8 |pages=1045–56 |year=2004 |doi=10.1002/joc.1054|bibcode = 2004IJCli..24.1045L }} | |||
| * NOAA / NESDIS / NGDC (2002) NOAA CD-ROM NGDC-05/01. This CD-ROM contains over 100 solar-terrestrial and related global data bases covering the period through April 1990. http://www.ngdc.noaa.gov/stp/CDROM/solar_variability.html | |||
| *{{Cite book |first1=S.K. |last1=Solanki |first2=M. |last2=Fligge |chapter=Long-term changes in solar irradiance |title=Proceedings of the 1st Solar and Space Weather Euroconference, 25-29 September 2000, Santa Cruz de Tenerife, Tenerife, Spain |editor-first=A. |editor-last=Wilson |publisher=ESA Publications Division |id=ESA SP-463 |year=2001 |url=http://adsabs.harvard.edu/full/2000ESASP.463...51S |isbn=9290926937 |pages=51–60}} | |||
| *{{Cite journal |first1=S.K. |last1=Solanki |first2=M. |last2=Fligge |title=Reconstruction of past solar irradiance |journal=Space Science Review |volume=94 |issue=1/2 |pages=127–38 |year=2000 |doi=10.1023/A:1026754803423 }} | |||
| *{{Cite journal |first1=George C. |last1=Reid |title=The sun-climate question: Is there a real connection? |journal=Rev. Geophys. |volume=33 |issue=Suppl |year=1995 |url=http://www.agu.org/revgeophys/reid00/reid00.html |doi=10.1029/95RG00103 |pages=535 |bibcode = 1995RvGeS..33..535R }} {{Dead link|date=January 2010}} Aeronomy Laboratory, NOAA/ERL, Boulder, Colorado. U.S. National Report to IUGG, 1991–1994 | |||
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