For the first time, scientists have used artificial intelligence not only to predict sunspots but also to correct the incomplete record of past sunspot activity.
A new paper just published in Advances in Space Research by Dr Victor Velasco Herrera, a theoretical physicist at the National Autonomous University of Mexico, Dr Willie Soon, an award-winning solar astrophysicist at the Harvard-Smithsonian Center for Astrophysics, and Professor David Legates, a climatologist at the University of Delaware and former director of the U.S. Global Change Research Program, predicts that the new 11-year solar cycle that has recently begun will show near-record low sunspot activity that will last until mid-century.
Both Dr Soon (in 2004) and Dr Velasco Herrera (in 2008) had previously published papers speculating that the first half of the 21st century would be a period of unusually few sunspots, potentially slowing the rate of global warming.
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The three scientists taught a machine-learning algorithm how to recognize underlying patterns and cycles in the past 320 years’ sunspot record. The algorithm then discovered a hitherto-unnoticed interaction between the 5.5-year solar half-cycles (blue) and the 120-year Gleissberg double cycles (red dotted lines) which allowed it to confirm the earlier predictions of a quiet half-century to come – predictions which are now shared by solar physicists.
That interaction between the two periodicities led the algorithm to indicate that from the 1730s to the 1760s, early in the modern sunspot record (the gray band below), sunspots appear to have been under-recorded: as the 120-year cycle approached its maximum amplitude, sunspots should have been more numerous than reported at the time.
The algorithm then predicted the sunspots from 2021 to 2100. It suggests that the current low solar activity is likely to continue until 2050:
There is still a reasonable hypothesis that solar weather affects the earth's climate, with lower solar sunspot activity correlated with cooler temperatures. A reasonable mechanism (the Svensmark hypothesis) has been postulated, that low solar activity allows more cosmic rays to reach the atmosphere, which seeds cloud nucleation, which shadow the earth and lower temperatures, but the link has not been "proven" to everyone's satisfaction, if that could happen. Certainly, previous periods of low sunspot activity, the Maunder and Dalton sunspots minima, periods of colder than average climate. This model predicts 3 more 11ish year cycles before the return of higher activity; plenty of time for a rigorous test of the model.
And let's not forget this is just a model (you could call it a hypothesis too), and will ultimately be tested against the way the cycles develop in the future. The literature is littered with tuned models that predicted the past well, and then fail to predict the future.