Approaching what is called solar minimum, the Sun’s average number of sun spots is dropping towards zero, with 54% of the days so far in 2019 spot free.
Sunspot numbers are visible evidence of overall solar activity. Some think that lower sunspot numbers over the last decade are indicative of the beginning of an extended period of lower solar activity and, potentially, a cooling of the Earth.
On average, there is an eleven year solar cycle where the Sun goes from a quiet mode, with almost no sunspots for extended periods, to an active mode, where multiple spots – some huge – rage on the surface of the Sun. Since tracking began in 1755, there have been 24 solar cycles, with the current cycle – cycle 24 – coming to a close as the number of spotless days rises.
“Solar maximum and solar minimum refer respectively to periods of maximum and minimum sunspot counts. Cycles span from one minimum to the next.”1
Over time, cycle length and solar activity have varied significantly. Sunspot cycles have ranged from as little as 8 years to over 14. Solar activity is currently dropping from an exceptionally high level that began in about 1940. The last period of similar magnitude was 9,000 years ago during the Boreal age.2
While it’s been proposed, thought and suggested that variations in solar activity affect climate, the current “scientific consensus” is that solar variation is but a minor driver for global climate change, “since the measured magnitude of recent solar variation is much smaller than the forcing due to greenhouse gases.”3 Some scientists think that an extended dip in solar activity during a period named the Maunder Minimum, which lasted from around 1645 to about 1715, intensified the Little Ice Age, a cool period that began in about 1300 and ended around 1850.4 As well, a lower rate of warming from 1998 to 2012 compared to the previous two to three decades has been attributed, in part, to reduced solar activity – “relatively weak solar activity made a small contribution to slowing surface warming in the early part of the new century.”5
While some studies suggest that solar activity will continue to weaken for an extended period and may produce cooling that could partially offset “disastrous effects of human-induced global warming,” other studies indicate that solar activity may be stronger during the next solar cycle.6
American and international scientists on NOAA’s Solar Cycle Prediction Panel (SCPP) say that the decline in solar activity amplitude, seen from cycles 21 through 24, is ending, with no extended Maunder-type minimum expected. The panel expects “Solar Cycle 25 will be very similar to Cycle 24: another fairly weak cycle.” Cycle 24 is declining to its end, with minimum expected within months. “Solar Cycle 25 may have a slow start, but is anticipated to peak with solar maximum occurring between 2023 and 2026” with an amplitude range of 95 to 130, “well below the average number of sunspots.” An official Sunspot Number prediction curve for Cycle 25 will be released later this year.7
The official prediction curve may likely be similar in format to the 2007 projection for Cycle 24, below.8
Nearing cycle minimum, Cycle 24’s progression curve, below, shows that the cycle’s smoothed curve double peaks were below both the high and low prediction curves.
Solar activity is now the lowest it has been in a century while the period from 1950 to 1995 “had the highest solar activity in perhaps 1000 years.” If the SCPP’s forecast of a Cycle 25 similar to Cycle 24 is wrong, how low might future solar activity get? “There are already suggestions that solar activity is moving towards a grand minimum along the lines of the Maunder Minimum, or perhaps a less severe one, like the Dalton Minimum (see Figure 2). Grand minima are by no means rare; they have likely occurred 7–9 times over the Holocene period (see, for example,Figure 7). It is therefore interesting to consider if the Sun is currently moving into a new grand minimum or just a period of low solar activity, and to think about the consequences for the Earth’s climate.”9
I’ve looked at sunspot status quite often over the duration of Cycle 24, usually at the beginning of each month when the when the sunspot number progression is updated, and have seen a number of different predictions of future climate impacts of changes in solar activity. One hypothesis predicts a sustained and significant cooling that will lower global temperature in the 2020s to that which prevailed in the 1980s. Another suggests that solar activity will fall 60% in 2030 to ‘mini ice age’ levels.
There have been a lot of articles recently speculating about the potential for global cooling – as well as others rejecting the possibility.
My personal thoughts on the matter is that these are all forecasts and hypotheses. We’ll likely not know for sure until whatever is going to happen is shown by empirical data to be already in progress.
- Solar cycle definition – Wikipedia (accessed May 21, 2019)
- Cycle history, “Sunspot numbers over the past 11,400 years have been reconstructed using Carbon-14-based dendroclimatology.” – Wikipedia (accessed May 22, 2019)
- Climate, IPCC consensus on climate change – Wikipedia (accessed May 22, 2019)
- No Global Cooling Miracle: Sun’s Activity Lull Will Stop Soon, Study Suggests – Space.com, December 7, 2018 (accessed May 22, 2019)
- Did global warming stop in 1998? – NOAA’s Climate.gov, September 4, 2018 (accessed May 22, 2019)
- Mini ice age ruled out – India Science Wire, December 7, 2018 (accessed May 23, 2019)
- Solar experts predict the Sun’s activity in Solar Cycle 25 to be below average, similar to Solar Cycle 24 – National Weather Service, April 5, 2019 (accessed May 24, 2019)
- NOAA Predicts Solar Cycle 24 – SpaceWeather.com, May 8, 2009 (accessed May 24, 2019)
- Force Majeure, The Sun’s Role in Climate Change – Heinrik Svensmark, ©2019 The Global Warming Policy Foundation, pdf (accessed May 24, 2019)
