Zapping clouds with lasers could tweak planet’s temperature

Laser blasts might help scientists tweak Earth’s thermostat by shattering the ice crystals found in cirrus clouds.

Zapping tiny ice particles in the lab forms new, smaller bits of ice, researchers report May 20 in Science Advances. Since clouds with more numerous, smaller ice particles reflect more light, the technique could combat global warming by causing the clouds to reflect more sunlight back into space, the scientists say.

Scientists from the University of Geneva and from Karlsruhe Institute of Technology in Germany injected water drops into a chilled chamber that mimics the frigid conditions high in the atmosphere, where wispy cirrus clouds live. The water froze into spherical ice particles, which the scientists walloped with short, intense bursts of laser light.
When the laser hits an ice particle, ultrahot plasma forms at its center, producing a shock wave that breaks the particle apart and vaporizes much of the ice. The excess water vapor left in the aftermath then condenses and freezes into new, smaller ice particles.
Applying this technique to clouds is “a long, long, long way in the future,” says physicist Mary Matthews of the University of Geneva, a coauthor of the study. Current laser technology is not up to the task of cloud zapping — yet. “What we are hoping for is that the advances in laser technology, which are moving faster and faster all the time, will enable high-powered, mobile lasers,” Matthews says.

But tinkering with cirrus clouds could backfire if scientists aren’t careful, says atmospheric scientist Trude Storelvmo of Yale University. The clouds also trap heat, through the greenhouse effect, so breaking up their ice particles could actually warm the Earth. The method“could potentially work, but only if you target certain types of cirrus clouds,” she says, such as those that are very thick.

There could also be warming if fossil fuels are burned to power the laser, says David Mitchell of the Desert Research Institute in Reno, Nev. “I think it’s really interesting research, but I’m just not seeing how it’s going to make the world a cooler place.”