EARTH

Can sunspots affect the weather?

By Jamie Carter published 30 August 22

How is the Earth’s climate is affected by what happens on the sun?

The sun has a major impact on Earth: It provides the light and energy that are vital to life on our planet and dramatically shapes Earth’s climate. But the sun’s activity is not always constant, and areas of the sun can cool or even erupt dramatically. Can the sunspots that appear on our star’s surface affect the weather here on Earth? And how?

It turns out that individual sunspots themselves don’t affect the weather, but the changes in solar activity that they reveal can affect temperature, wind and weather on the planet.

What are sunspots?

Sunspots are darker areas on the sun's surface that come and go over days. Sometimes there are several sunspots on the sun, and they can even occur in swarms. Other times the sun has no spots. Sunspots form when intense magnetic activity on the surface of the sun exposes the star's cooler layers. However, these cooler patches only occur in great numbers when the sun is particularly active. So while a particular dark spot may emit less energy than the rest of the sun, the increased activity of the sun overall sends slightly more energy toward Earth.

How do sunspots affect Earth?

There is no direct link between a single sunspot appearing and a short-term cooling in Earth’s temperature. “It will reduce the amount of light hitting the Earth by about 0.1%,” said Greg Kopp, a senior research scientist at the University of Colorado's Laboratory for Atmospheric and Space Physics. “It would take the Earth’s energy system several months of such continual decrease to notice this effect energetically, but a sunspot doesn't persist that long.”

Earth’s system is too large to be affected by small dimmings from sunspots on short timescales, said Kopp, who likens it to dumping a bathtub of ice into a swimming pool. “You wouldn’t notice a change in overall water temperature, but if you did it every hour for days on end, you would eventually feel a change,” he said.

But sunspots are a sign of solar activity. “Solar variability does cause Earth-climate effects on long timescales,” Kopp said. Climate is a 30-year average of weather(opens in new tab). “If the climate is warmer or cooler due to the sun, the average weather will be warmer or cooler too.”

However, there is absolutely no evidence that the sun's activity is responsible for the climate change we’ve seen over recent decades, which is caused by humans pumping greenhouse gasses into the atmosphere.