Editing Sunspot (section)

=== Longer-period trends ===
{{main|Solar cycle#Cycle history}}

Sunspot numbers also change over long periods. For example, during the period known as the modern maximum from 1900 to 1958 the [[solar maxima]] trend of sunspot count was upwards; for the following 60 years the trend was mostly downwards.<ref>{{cite web |url=http://sidc.oma.be/html/wolfaml.html |title=Sunspot index graphics |publisher=Solar Influences Data Analysis Center |access-date=27 September 2007}}</ref> Overall, the Sun was last as active as the modern maximum over 8,000 years ago.<ref name="pmid15510145">{{cite journal
| display-authors=4
| author=Solanki SK
| author2=Usoskin IG
| author3=Kromer B
| author4=Schüssler M
| author5=Beer J |date=October 2004
| title=Unusual activity of the Sun during recent decades compared to the previous 11,000 years
| journal=Nature |volume=431 |issue=7012 |pages=1084–1087
| url=http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/solanki2004.html
| doi=10.1038/nature02995 |pmid=15510145 |bibcode=2004Natur.431.1084S
| s2cid=4373732
}}</ref>

Sunspot number is correlated with the intensity of [[solar radiation]] over the period since 1979, when satellite measurements became available. The variation caused by the sunspot cycle to solar output is on the order of 0.1% of the solar constant (a peak-to-trough range of 1.3&nbsp;W·m<sup>−2</sup> compared with 1366&nbsp;W·m<sup>−2</sup> for the average solar constant).<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
 |access-date  = 2005-03-10
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20050315081547/http://www.grida.no/climate/ipcc_tar/wg1/244.htm
 |archive-date = 15 March 2005
}}</ref><ref name="AIPsolar">{{Cite web
| first=Spencer
| last=Weart
| title=The Discovery of Global Warming – Changing Sun, Changing Climate?
| editor-first=Spencer
| editor-last=Weart
| url=http://www.aip.org/history/climate/solar.htm
| publisher=[[American Institute of Physics]]
| date=2006
| access-date=2007-04-14
| archive-date=17 June 2006
| archive-url=https://web.archive.org/web/20060617030502/http://www.aip.org/history/climate/solar.htm
| url-status=dead
}}</ref>

{{multiple image
 |direction = horizontal
 |align= center
 |width1= 320
 |width2= 260
 |image1=Sunspot Numbers.png
 |image2=Sunspots 11000 years.svg
 |footer=400-year history of [[Wolf number|sunspot numbers]], showing [[Maunder Minimum|Maunder]] and Dalton minima, and the Modern Maximum (left) and 11,000-year sunspot reconstruction showing a downward trend over 2000 BC – 1600 AD followed by the recent 400 year uptrend
}}
[[File:Power spectrum of sunspot number, from 1945 to 2017.png|thumb|The daily sunspot number from 1945 to 2017, and its [[Spectral density|power spectrum]]. There are two prominent peaks corresponding to its 11-year cycle and its 27-day cycle due to solar rotation.<ref>{{Cite journal |last1=Le Mouël |first1=Jean-Louis |last2=Shnirman |first2=Mikhail G. |last3=Blanter |first3=Elena M. |date=2007-12-01 |title=The 27-Day Signal in Sunspot Number Series and the Solar Dynamo |url=https://doi.org/10.1007/s11207-007-9065-8 |journal=Solar Physics |language=en |volume=246 |issue=2 |pages=295–307 |doi=10.1007/s11207-007-9065-8 |bibcode=2007SoPh..246..295L |issn=1573-093X}}</ref>]]