Fig. 1: NASA analysis of the current sunspot number and forecast of the next solar maxima (likely in 2025). The historical average sunspot number for solar maxima is annotated on the right.
Discussion: According to NASA, solar cycle 25 began last September as solar minima ending the solar cycle 24 was completed. We’re currently on the uptick in sunspot activity as solar cycle 25 begins to strengthen (Fig. 1). The latest NASA forecast indicates solar cycle 25 will peak around 2025 at sunspot number 120. The forecast value is historically below the modern-day solar maxima (averaging 170 since the 1940’s) and also below the average solar maxima for the 1830’s to 1930’s (which averaged 135). Scientists have cited concern that the elongated solar minima (in 2005-2008) followed by a historically low solar maxima for solar cycle 24 (in 2014) might be a sign of a lengthy sunspot deficit last observed during the 1800-1830 Dalton Minimum. The solar cycle 24 peak sunspot number and solar cycle 25 forecast peak indicates no Dalton Minimum is likely although the values are historically quite low.
The probabilistic forecast indicates the most likely peak sunspot number is around 2025 at value 130 (Fig. 2). The upper limit forecast (5% risk) is near 250 while the lower limit forecast (5% risk) is around 70. A solar peak of 250 has occurred once before (around 1960).
Fig. 2: A probabilistic sunspot number forecast for solar cycle 25.
Summary: Solar cycle 25 is underway as solar minimum has concluded. NASA forecasts solar maxima for solar cycle 25 near or slightly weaker than solar cycle 24 (2014) and is projecting solar maxima in 2025. Although entering a period of historically low sunspot activity a Dalton Minimum is not expected. The upper limit forecast (sunspot number 250) is being cited by some forecasters as a likely scenario.