Here at the Almanac, we have long believed that solar activity can influence weather patterns here on Earth. Sunspot counts are at an almost 10-year low. Learn more about our Sun—from sunspots to solar flares to coronal mass ejections—and why it all matters.
What is Solar Activity?
First, let’s get to know the Sun. 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 few features to know:
- 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
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. We are currently in the 24th solar cycle since record-keeping began in 1755.
The highest number of sunspots in any given cycle is designated “solar maximum.” After some years of high activity, the Sun will ramp down with fewer sunspots or almost no sunspots. When it reaches its lowest number of sunspots, this is designated “solar minimum.”
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).
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
How Does Solar Activity Affect Weather and Earth?
As a technology dependent society, it’s important to know what the Sun is doing.
- GPS, satellites, and other high-tech systems in space can be caused 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.
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”—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.
Painting by Abraham Hondius, “The Frozen Thames, looking Eastwards towards Old London Bridge,” 1677. Image credit: Museum of London.
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.
When is the Solar Minimum?
We’re currently headed towards a solar minimum, forecasted to arrive in 2019 or 2020 as the Sun switches over from Solar Cycle 24 to Solar Cycle 25.
During solar minimum, solar flares and CMEs associated with sunspots subside. The Sun’s ultraviolet output dramatically decreases and the upper atmosphere of the planet cools, among other noticeable shifts. Also, we can see the development of longtime coronal holes—vast regions in the Sun’s atmosphere where the magnetic field opens up and allows solar streams to escape the Sun; this can cause space weather effects such as auroras as well as disruptions to communications and navigation systems. At a solar minimum, there can also be less atmospheric friction and “drag,” which could result in more space junk to watch out for.
There is nothing alarming expected; it’s just the normal ebb and flow of the Sun/Earth relationship.
Solar Cycle 24 has been a very quiet cycle, so it’s been difficult to tell exactly when Solar Cycle 25 will arrive. Here’s a very brief history of Solar Cycle 24:
Cycle 24 began in early 2008, specifically January 4th.
During 2008 and 2009, there were almost NO sunspots, a very unusual situation that had not happened for almost a century. Due to the weak solar activity, galactic cosmic rays were at record levels.
In 2010, the Sun’s record-breaking sleep ended. Sunspots started increasing slowly through 2011.
In February of 2012, sunspots peaked at 66.9, and then had a lull in activity until late 2013, when numbers began to slowly climb.
April of 2014 gave us a second peak at 81.9. Many cycles are double peaked, however, this is the first time the second peak was larger than the first peak (in February 2012).
During 2015, monthly sunspots declined steadily to their 50’s. During 2016, monthly sunspot numbers dropped to their 30’s and they just kept going down.
In 2017, monthly sunspot numbers declined to their 20’s.
In 2018, sunspot numbers are expected to drop further into the teens. While additional sunspots have appeared (including a massive one in February, 2018), they are increasingly rare as the Sun heads toward the solar minimum. As of August 28, there were 132 spotless days.
2019 and 2020 is expected to bring the solar minimum. It doesn’t mean the Sun goes dormant; the solar activity just changes form, and a new cycle will begin. Stay tuned!
Daily and Monthly Sunspot Numbers
What Does It All Mean?
Overall, quiet-to-average cycles, such as Cycle 24, 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.
Want to learn more about weather and space? Pick up your copy of The Old Farmer’s Almanac for this year’s long range weather prediction! Look inside the pages of the latest Almanac.