By The EditorsMarch 4, 2021NASA

Solar Cycle 25 is heating up! Will this new solar cycle be a wild one or a washout? Learn more about predictions regarding the next solar cycle, sunspots, solar flares, and auroras!

The Old Farmer’s Almanac pays attention to solar science as it’s one of the disciplines employed in the making of our long-range weather predictions. Our founder, Robert B. Thomas, who started this almanac back in 1792, believed that weather on Earth was influenced by sunspots, which are magnetic storms on the surface of the Sun. See how The Old Farmer’s Almanac predicts the weather.

Solar Cycle 25 began in December 2019 and is expected to peak in 2025, according to the Solar Cycle 25 Prediction Panel, an international group of experts co-sponsored by NASA and NOAA.

Specifically, December 2019 was the “solar minimum” or period of least solar activity in the 11-year solar cycle of the Sun. What are solar cycles? Learn more here.

• A solar cycle’s highs and lows are mainly tracked by “sunspots”—dark cool areas on the Sun’s surface. Learn more about sunspots.
• Sunspots release solar energy and are associated with “solar flares” which are intense bursts of radiation observed near the Sun’s surface and in close proximity to a sunspot group.
• Solar flares are sometimes accompanied by a coronal mass ejection (CME for short), which shoot actual matter (charged particles) into space. 
• If the solar eruption is very intense, the radiation that it releases can interfere with our radio communications here on Earth. 

Solar Cycle 24 lasted 11 years (December 2008 to 2019), which is the average length of a cycle, though it was the weakest cycle in terms of solar activity in 100 years. “Solar maximum” or the peak of Cycle 24 was in April 2014 with sunspots peaking at 114, well below average of 179.

The start of a new Solar Cycle (25) means there wil be increasing activity and more sunspots until roughly mid-2025.

However, the long-range prediction is that Solar Cycle 25 will below average, quiet, and cool. This is very similar to the Cycle 24—the weakest since record-keeping began in 1755.

“According to NOAA/NASA and international 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.”

• Specifically, the experts predicted: a peak in July, 2025 (+/- 8 months), with a smoothed sunspot number (SSN) of 115.
• The panel agreed that Cycle 25 will be average in intensity and similar to Cycle 24, and its peak will be similar as well.
• Additionally, the panel concurred that solar minimum between Cycles 24 and 25 will occur in April, 2020 (+/- 6 months). 

Contrary to NOAA/NASA’s models, there have been more recent studies with models which suggest that Solar Cycle 25 could be one of the strongest since record-keeping began.

Time will tell. For now, we know the Sun will be heating up as it takes its journey towards its solar maximum. 

Solar Cycle 24 was one of the quietest, weakest cycles in a century. (The prior cycle, 23, also had an extended period of very few sunspots.) For posterity, below is the very brief history of Cycle 24, which we were watching since it began in December of 2008—two years later than expected.

Spotless Days (through September 16, 2020)
2020 total: 181 days (70%)
2019 total: 281 days (77%)
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

–In 2008, Cycle 24 began (specifically on January 4).
–In 2011, sunspots started to build again. A monthly spike occurred in November 2011. 
–In 2012, the smoothed sunspot number reached a first peak of 98.3 (March, 2012).
–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. 
–In 2019, even more days were spotless (77%), hitting rock bottom in December.
–In 2020, sunspot counts were at their lowest at the start of year but started to pick up slowly.

What do inactive solar cycles mean in terms of climate and weather? 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, the occurrence of a new mini ice age is doubtful. 

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.

With the Sun entering the more active phase of its solar cycle, solar energy will be increasing until the solar maximum.

The months near the spring (March) and fall (October) equinox are the most geomagnetically active of the year. Strong storms are more likely to erupt, boosting the potential for both possible disruptions with satellites, radio communication, and power systems, but also awesome displays of the bright auroras!  

Interested in seeing nature’s light show? Read more about the Northern Lights.

Learn more about how solar activity affects the weather. 

Stay tuned for further updates! Want to learn more about weather and space? Pick up your copy of The Old Farmer’s Almanac!

The Sun is stirring from its latest slumber. As sunspots and flares, signs of a new solar cycle, bubble from the Sun’s surface, scientists wonder what this next cycle will look like. The short answer is, probably a lot like the last — that is, the past 11 years of the Sun’s life, since that’s the average length of any given cycle. But the longer story involves a panel of experts that meets once a decade, a fleet of Sun-studying satellites, and dozens of complicated models — all revolving around efforts to understand the mystifying behavior of the star we live with.

NASA scientists study and model the Sun to better understand what it does and why. The Sun has its ups and downs and cycles between them regularly. Roughly every 11 years, at the height of this cycle, the Sun’s magnetic poles flip — on Earth, that’d be like if the North and South Poles swapped places every decade — and the Sun transitions from sluggish to active and stormy. At its quietest, the Sun is at solar minimum; during solar maximum, the Sun blazes with bright flares and solar eruptions.

Solar cycle predictions give a rough idea of what we can expect in terms of space weather, the conditions in space that change much like weather on Earth. Outbursts from the Sun can lead to a range of effects, from ethereal aurora to satellite orbital decay, and disruptions to radio communications or the power grid. NOAA’s Space Weather Prediction Center is the U.S. government’s official source for space weather forecasts, watches, warnings, and alerts: With accurate predictions, we can prepare.

The work that researchers at NASA and around the world do to advance our solar activity models helps improve those forecasts. In turn, solar cycle forecasts give us a sense of how stormy the Sun will be over the next 11 years and how much radiation spacecraft and astronauts may face during heavy bouts of solar activity.

The Sun is stirring from its latest slumber. As sunspots and flares, signs of a new solar cycle, bubble from the Sun’s surface, scientists are anticipating a flurry of solar activity over the next few years. In this video, view the Sun from our space telescopes as it transitions from minimum to maximum.

Credits: NASA's Goddard Space Flight CenterDownload this video in HD formats from NASA Goddard's Scientific Visualization Studio

Modeling the Sun is a tricky business because scientists don’t fully understand the internal churning that causes this magnetic flip-flop. Computer models use equations to represent the Sun, but the star manages to elude them. If the Sun were a machine, it would have countless knobs and dials whose functions and sensitivities remain unknown.

“Over the last 40 years, we’ve come to observe the Sun in much greater detail,” said Lika Guhathakurta, program scientist of the Heliophysics Division at NASA Headquarters. “It’s produced a wealth of information, but quantifying and modeling the solar cycle remains challenging. We’re working against how variable the Sun is, and the complexity of what happens inside the Sun.”

Without fully understanding how the magnetic field, which drives solar activity, moves inside the Sun, scientists have to make some assumptions. The plight of solar modelers could be likened to that of weather forecasters — if they tried to forecast the weather by looking at just the upper atmosphere, and not the critical layers below. 

There are many approaches to modeling the Sun in order to develop solar cycle predictions. Some models use ground-based observations spanning hundreds of years; others may use satellite data, which has only been available for the past four decades or so. In recent years, some researchers have incorporated machine-learning tactics. Models may focus on different precursors scientists have identified are linked to solar activity: Earth’s magnetic field, which responds to the Sun’s, and the strength of the magnetic field at the Sun’s poles are most common.

“Part of the scientific process is whittling these questions down, and working in parallel on the same problem in different ways,” said Maria Weber, an astrophysicist at Delta State University in Cleveland, Mississippi. Each model is one tool among many. “We might find there are different tools that can get us the same outcome, and then you could pick the type that best suits you.”

It’s the job of the Solar Cycle Prediction Panel — co-sponsored by NASA and NOAA, the National Oceanic and Atmospheric Administration — to evaluate all of these models and release an official prediction representing the scientific community’s best efforts. Meeting every decade since 1989, the panel brings together experts from around the world, including Weber, who served on the panel for Solar Cycle 25. The discussions are known to occasionally get heated, a sign of the complex task at hand and the fervor each scientist has for their favorite models.

In the end, the scientists wrote their predictions on a little piece of paper, Weber said, and the debating began. “Ultimately, we all had to agree, whittling down and adjusting our estimates, so that people felt it best reflected everything we knew up to that point,” she said.

In March 2019, only the fourth time such a panel had convened, the 12 experts considered some 60 different models. In recent years, one seems to be especially successful: the polar magnetic field model. This uses measurements of the magnetic field at the Sun’s north and south poles. The idea is that the magnetic field at the Sun’s poles acts like a seed for the next cycle. If it’s strong during solar minimum, the next solar cycle will be strong; if it’s diminished, the next cycle should be too.

Together, they predicted dates for Cycle 25’s start and peak, and the peak sunspot number, an indicator of how strong the cycle will be. The more sunspots, the higher the sunspot number, and the more solar eruptions a cycle is expected to unleash.

Currently, the Sun’s poles are about as strong as they were at the same point in the last solar cycle, which scientists interpret as signs that Solar Cycle 25 will play out in similar fashion to Cycle 24. Solar Cycle 24 was a feeble cycle, peaking at 114 sunspots (the average is 179). 

Solar Cycle 25 is now underway and expected to peak with 115 sunspots in July 2025.

Visible light images from NASA's Solar Dynamics Observatory show the Sun at solar minimum in December 2019 and the last solar maximum in April 2014. Sunspots freckle the Sun during solar maximum; the dark spots are associated with solar activity.

Credits: NASA's Solar Dynamics Observatory/Joy Ng

Lisa Upton, co-chair of the Solar Cycle 25 Prediction Panel and solar physicist at Space Systems Research Corporation in Westminster, Colorado, compared their task to hurricane forecasting. Meteorologists often consult several models, each spitting out its own possible path a hurricane could take. “One of the lessons there is you don’t put too much faith in one model, but see what all of the models together can tell you and teach you,” Upton said. As a whole, a group of predictions is more likely to land on the right path.

Some have taken novel approaches to making these predictions. Scientists recently published a new way to survey the solar cycle: Instead of the traditional linear view of time, they used a mathematical technique to map the last 18 solar cycles onto a circle. What emerged was a more orderly pattern of behavior than expected from the Sun.

Their so-called solar clock is like a typical clock, where each roughly 11-year cycle can be described over 12 hours. Instead of the time of day, certain “times” correspond to high solar activity. Right now, the scientists say, it’s about 3 o’clock, near the first uptick in activity that comes at the beginning of each solar cycle. The scientists reported their findings in Geophysical Research Letters.   

“The most active Sun — in terms of solar eruptions — happens between 5:30 and about 10:00, when there’s a sharp drop-off in activity as the Sun moves toward minimum,” said Robert Leamon, a solar scientist on the study, based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Once we know where we are on the solar clock and can calculate the speed of the cycle we’re in, we can make much more precise predictions about when the next cycle of solar activity will start and stop.”

According to their clock, the Sun’s next quiet period will begin around the first half of 2027.

If Solar Cycle 25 meets the panel’s predictions, it should be weaker than average. Cycle 25 is also expected to end a longer trend over the past four decades, in which the magnetic field at the Sun’s poles were gradually weakening. As a result, the solar cycles have been steadily weaker too. If Solar Cycle 25 sees an end to this waning, it would quell speculations that the Sun might enter a grand solar minimum, a decades-to-centuries long stretch of little solar activity. The last such minimum — known as the Maunder minimum — occurred in the middle of what’s known as the Little Ice Age from the 13th to 19th centuries, causing erroneous beliefs that another grand minimum could lead to global cooling.

“There is no indication that we are currently approaching a Maunder-type minimum in solar activity,” Upton said. But even if the Sun dropped into a grand minimum, there’s no reason to think Earth would undergo another Ice Age; not only do scientists theorize that the Little Ice Age occurred for other reasons, but in our contemporary world, greenhouse gases far surpass the Sun’s effects when it comes to changes in Earth’s climate.

Eventually, scientists would like to issue weekly forecasts for the Sun, just like meteorologists do for Earth. But solar cycle and space weather forecasting have far to go. There are still questions about the Sun’s interior to answer and important data to collect.

“One of the things that’s exciting about being a solar physicist is that we’re at the forefront of this — there’s still all these questions that have yet to be answered,” Upton said. “There are still a lot of rocks to unturn.”

Solar Cycle 25 will continue to unfold, and scientists will keep tinkering with their models and watching to see how close their predictions come. It will be another five to six years before they can say who was right — or wrong — all along.

Related:

• Analysis Determines We Are in Solar Cycle 25
• Solar Cycle 25 Is Here. NASA, NOAA Scientists Explain What That Means
• How Scientists Around the World Track the Solar Cycle

By Lina Tran
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Last Updated: Dec 15, 2020Editor: Lina Tran