The Solar Cycle

Sunspots have been counted every day since 1610(opens in new tab), and the observations are kept at the Royal Observatory of Belgium's World Data Center for the Sunspot Index and Long-term Solar Observations(opens in new tab). This catalog of sunspots provides visual evidence for the solar cycle — a roughly 11-year period during which the number of sunspots goes from low to high and then back down to low.

Sunspots have been counted every day since 1610(opens in new tab), and the observations are kept at the Royal Observatory of Belgium's World Data Center for the Sunspot Index and Long-term Solar Observations(opens in new tab). This catalog of sunspots provides visual evidence for the solar cycle — a roughly 11-year period during which the number of sunspots goes from low to high and then back down to low.

Tracking sunspots is one way to track solar activity, “but it’s really the level of radiant energy the sun puts out across the wavelength spectrum that causes changes,” to Earth’s weather, Kopp said. For instance, shorter wavelengths of light produce more energy, so emitting more long wavelength light and less short wavelength light could, for instance, reduce the energy released by the sun.

The present Solar Cycle 25, which began in 2020(opens in new tab), looks like it will be stronger than predicted(opens in new tab). When there are a lot of sunspots there’s a very slight increase in the energy output from the sun, according to the National Weather Service(opens in new tab).

“Years having higher numbers of sunspots generally correspond with warmer times on the Earth, not cooler times,” Kopp said.

“It’s about 1.5 degrees Celsius [2.7 degrees Fahrenheit] warmer on average when it’s most active,” Kopp said. “That does have an effect both globally and regionally on Earth’s temperatures, winds, fires and weather patterns.”