We have long believed that solar activity can influence weather here on Earth. We are now in Solar Cycle 24, which has seen very low solar activity thus far. Learn more about solar activity—specifically solar flares and sunspots—and why it matters.
What is Solar Activity?
The Sun may seem like it’s a constant, always looking the same. However, just like planet Earth, the Sun has weather. It has storms. And its storms can affect Earth’s weather.
- Sunspots are magnetic storms on the surface of the Sun.
- Solar flares are strong flashes of x-rays and light energy that shoot off of the Sun’s surface into space at the speed of light.
- Coronal mass ejections (CMEs) are massive clouds of gas and magnetic matter that are eruptions spreading into space.
- 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.
Solar Flare. Credit: NASA
What is a Solar Cycle?
The number of sunspots (storms on the Sun) increase and decrease over time in a regular, approximately 11-year cycle, called the solar or sunspot cycle. More sunspots mean more solar activity. The highest number of sun spots in any given cycle is designated “solar maximum,” while the lowest number is designated “solar minimum.”
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?
Solar activity affects the Earth in many ways, some which we are still coming to understand.
- Damage to 21st-century 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 and satellites can be caused by a quiet Sun. Weak solar winds allow more galactic cosmic rays into the inner solar system.
- 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.
Solar Cycle 24 Progression
We are nine years into Solar Cycle 24, which means the 24th cycle since record-keeping began in 1755.
Sunspot counts have reached their lowest level in over 5 years.
Here are more details:
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.
The Sun’s record-breaking sleep ended in 2010. 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 steady 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.
September 6, 2017, brought an X9.3 solar flare—the most powerful recorded since at least 2008, when the current solar cycle began.
Solar eruptions are increasingly rare as the Sun heads toward the solar minimum.
An X9.3 class solar flare flashes in the middle of the Sun on Sept. 6, 2017. This image was captured by NASA’s Solar Dynamics Observatory and shows a blend of light from the 171 and 131 angstrom wavelengths.
Daily and Monthly Sunspot Numbers
What Does All This 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, they also raise the question of whether an eventual warming cycle could lead to more rapid warming on Earth than expected.
When is the Solar Minimum?
The minimum for this 11-year sunspot cycle is expected in 2019 to 2020. It doesn’t meant the Sun goes dormant; the solar activity just changes form.
During solar minimum, sunspots and solar flares subside. The Sun’s ultraviolet output will dramatically decrease and the upper atmosphere of the planet may cool, 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!
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.