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The solar eclipse may drive away cumulus clouds. Here's why that worries some scientists.

Scientists say the unusual cloud activity observed during past eclipses has implications for climate engineering efforts to mitigate the effects of global warming.

Eric Lagatta
USA TODAY

When the moon passes in front of the sun during a solar eclipse and ushers in an uncharacteristic darkness, nature tends to react.

Birds cease their chirping. Buzzing bees return to their hives. And nocturnal creatures like bats are sure to stir from their daytime slumber.

But it's not just animals whose activity is disrupted by solar eclipses, such as the total eclipse that will sweep across North America on April 8. New research suggests that cloud activity also alters during the celestial event, which occurs when the orbiting moon passes between the sun and Earth and blocks the sunlight.

Clouds, particularly shallow cumulus clouds, tend to vanish during a solar eclipse. What's more, it doesn't take much to cause their dissipation: Just 15% of the sun needs to be obscured by the moon before some clouds disappear, according to new research published Feb. 12 in the journal "Communications Earth & Environment."

That may be an interesting factoid to share with all your skygazing friends eagerly awaiting the Great American Eclipse, but scientists say it has implications for climate engineering efforts to mitigate the effects of global warming, too.

"If we eclipse the sun in the future with technological solutions, it may affect the clouds," explained Victor Trees, the geoscientist who led the team of researchers.

The sun is eclipsed by the moon and the sun's corona can be seen during a total solar eclipse on Monday, August 21, 2017. This image was captured in Deep Creek, Bryson City, North Carolina.

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Researchers study cloud data from African eclipses

Satellite measurements during eclipses have been notoriously tricky to analyze for data because algorithms don't take into account the decrease in sunlight that results in dark spots on cloud maps.

However, researchers at the Royal Netherlands Meteorological Institute and Delft University of Technology used a new method to recover the satellite measurements, Trees said in a news release. By calculating the percentage of the sun that is obscured for each location and time on Earth, the researchers said they were able to accurately restore satellite measurements during eclipses.

The researchers then applied the method to data collected between 2005 and 2016 during three solar eclipses in Africa. They found that cumulus clouds exhibit unusual characteristics not observed when there is no solar eclipse: Specifically, the clouds start to vanish "on a large scale" when just 15% of the sun is obscured, not to return until the eclipse has ended, Trees wrote.

To find an explanation, the team turned to cloud modeling software called DALES. The simulations they conducted showed that when the sunlight is blocked, the Earth's surface cools enough to reduce the updrafts of warm air carrying water vapor from the surface, which are how cumulus clouds form.

The same effect was not observed above the ocean since seawater does not cool down fast enough for cumulus clouds to dissipate.

Until the new research, it was unknown just how strongly clouds responded to the the occurrence of any kind of solar eclipse, Trees said.

"Even without a solar eclipse, clouds are constantly changing," he wrote.

Millions will witness 2024's total solar eclipse, which will occur months after a different sort of eclipse, an annular eclipse, occurred in the United States.

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The research's publication came just about two months before a total solar eclipse is set to chart a path of totality across North America for the first time since 2017.

Millions of Americans already live along the 115-mile-long path projected to wend through 13 U.S. states, as well as Mexico and Canada – and they'll likely be keeping their fingers crossed for clear skies.

Daylight will give way to sudden darkness for a few brief minutes that day as the orbiting moon will appear as the same size as the sun, completely blocking its light.

When "totality" occurs, skygazers will be able to remove their protective safety glasses and gaze with their naked eyes upon the outmost layer of the sun's atmosphere known as the corona.

'A warning for climate engineering'

Knox County Mayor Tim Burchett watches for the total solar eclipse in 2017 during a watch party in Tennessee. Special glasses such as the ones those pictured are wearing will be required until the moon fully eclipses the sun and blocks its light.

The new research also comes at a time when strategies to artificially cool a warming planet are being proposed.

Some concepts – such as placing reflective solar sails into space, or sending aerosols into the stratosphere – create an effect not unlike a solar eclipse, according to Trees. But because even just partial eclipses can send clouds away, "this could be a warning for climate engineering," he wrote.

Because cumulus clouds can easily transform into rain clouds, the team's finding suggests climate geoengineering that involves blocking sunlight could effect weather patterns and precipitation.

There's also a much more obvious reason why the absence of clouds would undermine the intentions of geoengineering.

"Fewer clouds could partly oppose the intended effect of climate engineering," Trees wrote, calling for further research into the phenomenon. "Clouds reflect sunlight and thus actually help to cool down the Earth."

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com