Here’s the latest on Solar Cycle 24 and Solar Cycle 25—along with forecasts about when we will hit the solar minimum and predictions regarding the next solar maximum.
What is the Current Solar Cycle?
Solar cycles typically occur in 11-year periods (but can range from eight to 14 years). (What are solar cycles? Learn more here.)
We’ve been in Solar Cycle 24 for over 11 years. The end of a cycle occurs when the solar cycle reaches the solar minimum, when the Sun is least active.
As sunspots rapidly decline, experts from NOAA/NASA that Solar Cycle 24 is slowly winding down and Solar Cycle 25 seems to be sputtering to life.
Cycle 24 should reach its minimum between late 2019 and September 2020. The two cycles will overlap as Cycle 24 decays and Cycle 25 begins.
Solar Cycle 24: Journey to Solar Minimum
Solar Cycle 24 has been one of the quietest, weakest cycles in a century. (The prior cycle 23 also had an extended period of very few sunspots.) Here’s a very brief history of Cycle 24 (which we’ve been watching at The Old Farmer’s Almanac since it began in December of 2008—two years later than expected!).
Spotless Days (As of October 11, 2019)
2019 total: 207 days (73%)
2018 total: 221 days (61%)
2017 total: 104 days (28%)
2016 total: 32 days (9%)
2015 total: 0 days (0%)
2014 total: 1 day (<1%)
2013 total: 0 days (0%)
2012 total: 0 days (0%)
2011 total: 2 days (<1%)
2010 total: 51 days (14%)
2009 total: 260 days (71%)
2008 total: 268 days (73%)
2007 total: 152 days (42%)
2006 total: 70 days (19%)
Brief History and Highlights of Cycle 24
Cycle 24 began in early 2008, specifically January 4.
In 2011, sunspots started to build again. A monthly spike occurred in November 2011.
In early 2012, the smoothed sunspot number reached a first peak of 98.3 (March, 2012).
But April 2014 brought a second peak. The smoothed sunspot number reached a second peak of 116.4 (April, 2014). This became the official maximum. It’s not unusual to have a double peak, but it’s rare that the second peak is larger than the first. Cycle 24’s peak still ranks as the weakest since Cycle 14, which peaked in 1906.
From 2015 to 2017, sunspots kept dropping steadily from 0% spotless days in 2015 to 28% spotless days in 2017.
In 2018, 61% of the days were spotless! We went weeks at a time without a single spot on the Sun’s face.
Thus far, in 2019, even more days have been spotless (73%).
Solar Cycle 24 does indeed appear close to the end of its lifespan.
With the total lack of sunspot activity, some scientists say that there are signs that the Solar Minimum is underway and Solar Cycle 25 is sputtering to life.
Solar Cycle 25 Coming to Life
In July, 2019, a sunspot designated AR2744 emerged in the Sun’s southern hemisphere, as observed by NASA’s Solar Dynamics Observatory:
We know that this sunspot is part of Solar Cycle 25 because of the magnetic polarity. It’s a little complicated, but sunspots switch polarities from one solar cycle to the next.
Southern sunspots from Solar Cycle 24 have a -/+ polarity. The July sunspot, AR2744, is the opposite: +/-.
There have been some short-lived sunspots but AR2744 was long-lasting and possibly the first official sunspot of Solar Cycle 25.
Other Indications That Solar Cycle 24 is Ending
We also know that the Earth’s upper atmosphere has started to cool. Data from NASA’s TIMED satellite show that the thermosphere (the uppermost layer of air around our planet) shows that “We see a cooling trend,” says Martin Mlynczak of NASA’s Langley Research Center. “High above Earth’s surface, near the edge of space, our atmosphere is losing heat energy. If current trends continue, it could soon set a Space Age record for cold.”
In addition, the low solar energy has resulted in increased radiation, as measured by high-altitude balloons above the U.S. Cosmic rays can alter the flow of electricity through Earth’s atmosphere, trigger lightning, potentially alter cloud cover, and affect aeronautical and airline travelers.
Image: The TIMED satellite monitoring the temperature of the upper atmosphere.
Solar Cycle 25 Predictions
According to NOAA/NASA experts: “Cycle 25 will be similar in size to cycle 24, preceded by a long, deep minimum. Solar Cycle 25 may have a slow start, but is anticipated to peak with solar maximum occurring between 2023 and 2026, and a sunspot range of 95 to 130. This is well below the average number of sunspots, which typically ranges from 140 to 220 sunspots per solar cycle.”
In other words, Solar Cycle 25 may be quite similar to Cycle 24 with a long minimum periods and a weak peak.
The panel hopes to release a final, detailed forecast for Cycle 25 by the end of 2019.
If the Solar Minimum for Cycle 24 is as similar to the 2008 one as it appears, the Sun dimmed by 0.1%; Earth’s upper atmosphere collapsed, allowing space junk to accumulate; solar wind slowed down so cosmic rays (normally repelled by solar wind) surged to Space Age highs.
Much of this is the normal ebb and flow of the Sun/Earth relationship, which can be stormy. That said, if the Sun goes through a more prolonged solar minimum, then Earth could experience a cooler period.
Prospects of a Mini-Ice Age
Overall, quiet-to-average solar cycles with deep solar minimums mean a cooling pattern. In other words, temperatures become colder than they would have been otherwise. Sunspots are similar to a bathtub of lukewarm water; if you trickle in cold or hot water, it may take a while to notice the difference.
If this cooling phase on Earth, however, is offset by any warming caused by increasing greenhouse gases, it also raises the question of whether an eventual warming cycle could lead to more rapid warming on Earth than expected.
Could a deep, long-lasting solar minimum lead to extreme cold such as a mini-ice age? In the 17th century, the 70-year Maunder Minimum brought a very cold period to the Earth.
- According to solar radiation expert Judith Lean, PhD, of the Naval Research Laboratory, if we do have a “Maunder Minimum,” it would not be a return to the “Little Ice Age.”
- She points to a current global surface temperature that’s about 1.8 degrees Fahrenheit warmer than at the time of the Maunder Minimum and says that a return to a Maunder Minimum phenomenon would lead to a cooling by only one-tenth of a degree C or 0.18 degree F.
Also, Lisa Upton, Ph.D., solar physicist with Space Systems Research Corp., states that “the expectation that Cycle 25 will be comparable in size to Cycle 24 means that the steady decline in solar cycle amplitude, seen from cycles 21 to 24, has come to an end and that there is no indication that we are currently approaching a Maunder-type minimum in solar activity.”
In other words, a new mini-ice age is doubtful.
Stay tuned for further updates! Want to learn more about weather and space? Pick up your copy of The Old Farmer’s Almanac!