Study links solar activity to Earth's climate

During a solar maximum, climate changes occur in North America, according to a recent study

April 13, 1999
Web posted at: 11:40 AM EDT

NASA researchers have found the link between solar activity and Earth's climate -- it was blowing in the wind.

Scientists had presumed for decades that activity on the surface of the sun and winds on Earth were related somehow but were missing a key ingredient, according to Drew Shindell, a climate researcher at Nasa's Goddard Institute for Space Studies in New York, N.Y.

What previous studies had neglected to take into account, according to Shindell's research published in the April 9 issue of Science, was the effect of increased solar activity on the ozone layer or the complex chemistry of the upper atmosphere.

"When we added the upper atmosphere's chemistry into our climate model, we found that during a solar maximum major climate changes occur in North America," said Shindell. The climate changes were being caused by stronger westerly winds. In addition, Shindell said wind speeds and directions all over the Earth's surface were influenced.

The sun has an 11-year cycle where it goes from a solar maximum to a solar minimum. The energy released by the sun during this cycle only fluctuates one-tenth of one percent.

When the solar cycle is at a maximum, it puts out a larger percentage of high-energy radiation, which increases the amount of ozone in the upper atmosphere. The increased ozone warms the upper atmosphere and the warm air affects winds all the way from the stratosphere to the Earth's surface.

"The change in wind strength and direction creates different climate patterns around the globe," said Shindell.

But what effect does this have on global warming?

None, said Shindell. His study confirms that changing levels of energy from the sun are not a major cause of global warming.

Many scientists have argued that the radiation change in a solar cycle — an increase of two to three tenths of a percent over the 20th century — are not strong enough to account for the observed surface temperature increases. The Goddard Institute for Space Studies model agrees that the solar increases do not have the ability to cause large global temperature increases, leading Shindell to conclude that greenhouse gases are indeed playing the dominant role.

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