Here at the Almanac, we believe that solar science, the study of sunspots and other solar activity, can influence weather here on Earth. In this article, we explain the basics of solar activity, solar cycles, and what's up with the Sun now.
What Is Solar Activity?
The Sun is always active. It 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 intense blooms of radiation that come from the release of the magnetic energy associated with sunspots. The NOAA ranks solar flares using five categories from weakest to stongest: A, B, C, M, and X. Each category is 10 times stronger than the one before it. Within each category, a flare is ranked from 1 to 9, according to strength, although X-class flares can go higher than 9. According to NASA, the most powerful solar flare recorded was an X28 (in 2003).
- Coronal mass ejections (CMEs) are bursts of solar material (clouds of plasma and magnetic fields) that shoot off the sun's surface. 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: jpl.nasa.gov
What is a Solar Cycle?
The number of sunspots increase and decrease over time in a regular, approximately 11-year cycle, called the solar or sunspot cycle. The exact length of the cycle can vary. More sunspots mean increased solar activity—flares and CMEs. The highest number of sun spots in any given cycle is designated "solar maximum," while the lowest number is designated "solar minimum."
Solar Minimum: According to NOAA and NASA, the sunspot cycle hit an unusually deep bottom from 2007 to 2009. In fact, in 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.
Solar Maximum: The Sun's record-breaking sleep ended in 2010. We are now in Solar Cycle 24, headed for a peak or solar maximum in the year 2013. When it arrives, the peak of the 11-year sunspot cycle will bring more solar flares, CMEs, and geomagnetic storms. That said, most experts predict that this cycle will be exceptionally quiet, producing a lower number of sunspots than the average cycle.
In addition, Cycle 24 took a long time to get under way. Some theorists believe that there is a correlation between Earth's temperatures and both the level of solar activity and the length of the solar cycle. The low solar activity levels and the delayed start to the solar cycle indicate that we're in a cooling phase.
Of course, even a below-average sunspot count does not preclude a large solar flare—which could cause billions of dollars in damage to the world's high-tech infrastructure.
Eleven years in the life of the Sun, spanning most of solar cycle 23, as it progressed from solar minimum (upper left) to maximum conditions and back to minimum (upper right) again, seen as a collage of ten full-disk images of the lower corona. 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.
- An active Sun can generate geomagnetic storms that damage 21st-century satellites and other high-tech systems in space—from GPS navigation to power grids to air travel to financial services.
- A quiet Sun usually means weak solar winds, which may allow more galactic cosmic rays into the inner solar system. This can pose radiation hazards for astronauts and satellites.
- Weather on Earth can also be affected. Recently, NOAA scientists finally concluded that four factors determined global temperatures: carbon dioxide levels, volcanic eruptions, Pacific El Niño pattern, and the Sun's activity.
There is also historical evidence that long-term periods of global cold, rainfall, drought, and other weather shifts relate to solar cycle activity:
- Times of depressed solar activity seem to correspond with times of global cold. For example, during the 70-year period from 1645 to 1715, few, if any, sunspots were seen, even during expected sunspot maximums. Western Europe entered a climate period known as the "Maunder Minimum" or "Little Ice Age." Temperatures dropped by 1.8 to 2.7 degrees Fahrenheit.
- Times of increased solar activity have corresponded with global warning. During the 12th and 13th centuries, the Sun was active, and the European climate was quite mild.
Yearly-averaged sunspot numbers from 1610 to 2008. Researchers believe upcoming Solar Cycle 24 will be similar to the cycle that peaked in 1928, marked by a red arrow. Credit: NASA/MSFC
What's Up With the Sun Now?
Late 2009 brought a burst of activity, and December ended with a flurry of sunspots.
During 2010, solar activity started to increase activity with several intense periods of eruption, sometimes all at once. NASA stated that "the Sun is waking up from a deep slumber, and the next few years could bring much higher levels of solar activity."
During 2011, the Sun had a year of activity, but low activity. Many researchers believed the upcoming solar maximum would be weak.
During 2012, the Sun was more active, unleasing some sizeable X-class flares and many M-class flares. As the Sun hurls occasional CMEs directly toward Earth, we have seen some of the most spectular displays of northern lights in years.
There were 0 sun-spotless days in 2012 as compared to 2 spotless days in 2011 , 51 spotless days in 2010, and 260 spotless days in 2009. See a record of solar activity  from the NASA Solar Dynamics Observatory.
As of January 2013, one of the biggest sunspots of the current solar cycle (named AR1654) is now turning toward Earth.
The next solar maximum is still expected in 2013.
The Solar Max of Cycle 24
Most solar science experts believe that both Cycle 24 and the following cycle (25) may be relatively quiet-to-average, leading to a cooling pattern over the next few decades. If this cooling phase on Earth 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.
To quote Bob Berman , astronomer for The Old Farmer's Almanac, "If the upcoming solar max of Cycle 24 is normal or robust, and especially if an El Niño follows it 2 years later (as often happens), then the middle of this decade will be the hottest period since humans arrived on Earth. However, if the upcoming maximum is wimpy, as most solar researchers expect, or if the Sun is now entering an extended period of low activity, that is the best thing it could possibly do for us. Such a scenario would mitigate climate change. Essentially, the Sun has been buying us time."
Stay tuned. We'll continue to update this sunspot page regularly to keep you informed.
In the meantime, enjoy the Sun's light show! This colorful event is caused by solar winds. Learn more about the aurora borealis .