Modern Maximum
{{Short description|Period of high solar activity beginning in 1914}}
{{cite check|date=October 2021}}
Image:Sunspot Numbers.png observations showing the recent elevated activity.]]
The Modern Maximum was found by Sami Solanki, Ilya G. Usoskin and colleagues{{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|doi = 10.1038/nature02995|accessdate = 17 April 2007|pmid = 15510145|issue = 7012|bibcode = 2004Natur.431.1084S| s2cid=4373732 }}, {{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}} as the period of unusually high solar activity{{cite journal |author = Usoskin I.G. | author-link=Ilya G. Usoskin|title = A History of Solar Activity over Millennia|journal = Living Reviews in Solar Physics|volume = 14|issue = 3|pages = 3|date = 2017|doi = 10.1007/s41116-017-0006-9|bibcode = 2017LRSP...14....3U |arxiv = 0810.3972| s2cid=195340740 }} [https://link.springer.com/content/pdf/10.1007%2Fs41116-017-0006-9.pdf PDF Copy] which began with solar cycle 15 in 1914. It reached a maximum in solar cycle 19 during the late 1950s and may have ended with the peak of solar cycle 23 in 2000, as solar cycle 24 is recording, at best, very muted solar activity.{{Cite journal | doi = 10.1023/A:1012745612022| year = 2001| last2 = Echer| last3 = Vieira| last4 = Nordemann| pages = 179–191| volume = 203| issue = 1| last1 = Rigozo| first2 = E.| first3 = L. E. A.| first4 = D. J. R.| journal = Solar Physics| first1 = N. R.| title = Reconstruction of Wolf Sunspot Numbers on the Basis of Spectral Characteristics and Estimates of Associated Radio Flux and Solar Wind Parameters for the Last Millennium|bibcode = 2001SoPh..203..179R | s2cid = 117574927}}{{failed verification|date=October 2021}}{{update inline|date=August 2024}} Another proposed end date for the maximum is 2007, with the decline phase of Cycle 23.{{citation needed|date=October 2021}} In any case the low solar activity of solar cycle 24 in the 2010s marked a new period of reduced solar activity. However the on-going (as of 2025) solar cycle 25 significantly exceeded its predicted low maximum.[https://climateimpactcompany.com/solar-cycle-25-continues-to-strengthen-rapidly-3/ Solar Cycle 25 Continues to Strengthen Rapidly]
This maximum period is a natural example of solar variation, and one of many that are known from proxy records of past solar variability. The Modern Maximum reached a double peak once in the 1950s and again during the 1990s.