Can we combat climate change by brightening clouds?

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group of scientists gathered on an aircraft carrier flight deck this month to test a technology designed for a solar geoengineering method called "cloud brightening."

The idea is to make clouds more reflective, so they bounce more of the sun’s rays back out to space, theoretically cooling the Earth and combating global warming.

It’s the first time such a test has taken place outdoors in the United States.

"To actually be there to see it in operation for the first time was pretty amazing to me," said Robert Wood, a professor of atmospheric sciences at the University of Washington’s College of the Environment. He’s the lead scientist working on cloud brightening.

When thinking of brightening, Wood said clouds won't appear brighter from the ground. Instead, it is "brighter from the perspective of outer space looking at the Earth."

"The earth gets a little bit brighter, which means that it's reflecting a little bit more sunlight," he said.

While this may sound like science fiction come to life, humans are inadvertently brightening clouds already.

Ships burn fossil fuels, which release sulfates, and these small particles alter the clouds in their wake.

"We haven't seen the world getting cooler because of that," Wood said. "That's because the carbon dioxide and the other greenhouse gasses have overwhelmed that effect. But the effect is still there."

Now, Wood and his team are testing equipment they hope can brighten clouds without burning greenhouse gas-emitting fossil fuels.

On the aircraft carrier in San Francisco Bay, the team tested a device called CARI or the Cloud Aerosol Research Instrument, which sprays a non-toxic aerosol, similar to salt water.

But they weren’t aiming that spray at clouds. For this experiment, researchers were shooting finely tuned particles at an array of sensors sitting on construction lifts above the carrier deck. This test was designed to help the cloud brightening team dial in whether particles from CARI , the sprayer, will remain the proper size for cloud brightening under different outdoor conditions.

"Clouds respond to different sized particles in different ways. If you put particles in that are tiny, that cloud doesn't really respond to them," Wood said. "If you put particles in that are too big, then those particles can actually trigger the cloud to produce precipitation."

Wood said there’s a long road of testing and further research, a decade or more, before his cloud brightening team would potentially be attempting to cool the Earth.

"We really want to be open about what we're doing and use it to inform people about what's going on, not only with the idea of solar radiation modification, but the idea of understanding climate in general," Wood said.

Supporters of this technology argue it could someday play a part in keeping global temperatures within a habitable range.

The idea of solar geoengineering raises ethical and practical questions about the risks of fundamentally altering the natural world. Then there’s the question of who decides when and how to actually use these technologies outside of tightly controlled experimental settings.

Listen to Soundside’s full conversation with Robert Wood by clicking the play icon at the top of this story.