Here at the Almanac, we have long believed that the Sun’s weather cycles—called “solar cycles” or “sunspot cycles“—influence weather patterns here on Earth. What causes a solar cycle? Which solar cycle are we in? Are we in a solar minimum or maximum? Get the update on your Sun—updated regularly!
All weather on Earth, from the surface of the planet out into space, begins with the Sun. Both space weather and terrestrial weather (the weather we feel at the surface) are influenced by the small changes the Sun undergoes during its solar cycle—referred to as “solar activity.”
What is Solar Activity?
Our burning star may seem like it’s a constant ball, always looking the same. However, just like planet Earth, the Sun has weather. It has storms. And its storms can affect Earth’s weather. Here are a few features:
- Sunspots are dark, cool spots on the Sun. Think of them as caps to a magnetic storm that is brewing just below the solar surface. The Sun’s magnetic fields are moving around, getting twisted and concentrated in these regions. Learn more in “What Are Sunspots?”
- Solar flares appear as flashes of light on the Sun, and are associated with sunspots. Occasionally, when powerful magnetic fields reconnect, they explode and break through the sun’s surface! There is a sudden burst light energy and X-rays. Flares are classified according to their strength. The smallest ones are B-class, followed by C, M and X, the largest. M-class flares can cause brief radio blackouts at the poles and minor radiation storms that might endanger astronauts.
- Coronal mass ejections (CMEs) are massive clouds of particles that spread into space! Large pieces of magnetic energy are hurled from the Sun into interplanetary space at speeds up to several million mph. CMEs can occur when filaments/prominences become unstable and fly away from the Sun. We call this a filament/prominence eruption.
- Other solar events include solar wind streams that come from the coronal holes on the Sun and solar energetic particles that are primarily released by CMEs.
See the Difference Between Solar Flares and CMEs
How Does Solar Activity Affect Earth?
The Sun affects both weather and technology (which we’re increasingly dependent on) here on Earth. For example:
- GPS, satellites, and other high-tech systems in space can be affected by an active Sun. Some of these systems are not protected by Earth’s atmospheric layers, so large solar flares have the potential to cause billions of dollars in damage to the world’s high-tech infrastructure—from GPS navigation to power grids to air travel to financial services.
- Radiation hazards for astronauts can be caused by a quiet Sun. Weak solar winds allow more galactic cosmic rays into the inner solar system. Even airline pilots and crew can get a higher dose of radiation during solar storms.
- Weather on Earth can also be affected. According to Bob Berman, astronomer for The Old Farmer’s Almanac, NOAA scientists have now concluded that four factors determine global temperatures: carbon dioxide levels, volcanic eruptions, Pacific El Niño pattern, and the Sun’s activity.
- Global climate change, including long-term periods of global cold, rainfall, drought, and other weather shifts, may also be influenced by solar cycle activity.
What is a Solar Cycle?
Traditionally, the number of sunspots (storms on the Sun) increase and decrease over time in a regular, approximately 11-year cycle, called the solar cycle or sunspot cycle.
Scientists measure solar cycles by keeping track of the number of sunspots appearing on its surface.
Eleven years in the life of the Sun from 1980 (start of solar maximum) to 1986 (near minimum) to 1989 (near maximum again). Credit: NASA
Record-keeping of solar cycles began in 1755. We are now nearing the end of Solar Cycle 24, approaching the solar minimum.
- By solar minimum, we mean the lowest number of sunspots. After some years of high activity, the Sun will ramp down with fewer sunspots or almost no sunspots. The temperature cools.
- Conversely, solar maximum is the highest number of sunspots in any given cycle. A new cycle starts with a “solar maximum” littered with solar storms and sunspots. The temperature warms.
As the cycles can overlap, it can be challenging to predict when a new cycle begins. However, there are some clues. For example, sunspots tend to form nearer the equator as the cycle winds down (and at higher latitudes when a new cycle begins).
The Maunder Minimum or “Little Ice Age”
Times of depressed solar activity seem to correspond with times of global cold.
- For example, between 1645 and 1715—during what we now call the “Maunder Minimum”—sunspots were exceedingly rare.
- Specifically, there were only about 50 sunspots (instead of the usual 40 to 50 thousand) and harsh winters.
- For 70 years, temperatures dropped by 1.8 to 2.7 degrees Fahrenheit. Seven decades of freezing weather led to shorter seasons and ultimately food shortages.
Conversely, times of increased solar activity have corresponded with global warming. During the 12th and 13th centuries, the Sun was active, and the European climate was quite mild.
Painting by Abraham Hondius, “The Frozen Thames, looking Eastwards towards Old London Bridge,” 1677. Image credit: Museum of London.
Current Solar Cycle 24
Solar Cycle 24 has been one of the quietest, weakest cycles in a century and is wrapping to an end. (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 since it began in 2008—two years late!).
Spotless Days (As of July, 2019)
2019 total: 121 days (63%)
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%)
Cycle 24 began in early 2008, specifically January 4th.
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 early 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.
As of July 11, 2019, 63% of the days have been spotless—similar to an entire decade ago!
Start of Solar Cycle 25?
According to forecasts, the solar minimum should begin between 2019 and 2020.
Cycle 24 does indeed appear close to the end of its lifespan. With the total lack of sunspot activity, the Solar Minimum may be underway now.
On July 2, Spaceweather.com reported: “This week, a cluster of small sunspots from the next solar cycle bubbled up to the surface of the sun. The dark cores didn’t last long, but they had the unmistakable magnetic signature of Solar Cycle 25.:
On July 8, it was reported that a reversed-polarity sunspot has broken through the surface of the sun (the second time this month). This latest “backwards sunspot” could mark the official beginning of new Solar Cycle 25.
Supporting this theory, 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.
If this Solar Minimum 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 cold period.
Will the next sunspot cycle be more “normal” or will we again see a decreased number of spots?
Prospects of Mini-Ice Age
Could a deep, long-lasting solar minimum lead to extreme cold such as a mini-ice age?
Overall, quiet-to-average cycles, such as Cycle 24, and a solar minimum phase normally 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.
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.
In other words, a 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!