Laser blasts might one day help scientists tweak Earth’s temperature. To do that, the lasers would be aimed at thin, wispy cirrus clouds. By shattering the ice crystals in them, those laser zaps might help cool the ground-level climate.
It’s a clever idea, although not ready for prime time. It also has its critics.
In the new study, researchers zapped tiny ice particles in the lab. This formed new, smaller bits of ice, they reported May 20 in Science Advances. Clouds with more — and smaller — ice particles reflect more light. So if used on clouds, this laser therapy might cause them to reflect more sunlight back into space. And that, the scientists propose, might offer one way to help combat global warming.
The scientists work at the University of Geneva in Switzerland and the Karlsruhe Institute of Technology in Germany. They injected water droplets into a chilled chamber. Its frigid conditions mimic those high in Earth’s atmosphere, where cirrus clouds live. The water froze into spherical ice particles. The scientists then walloped these spheres with short, intense bursts of laser light.
As each was hit, ultrahot plasma formed in the center of the ice particle. That produced a shock wave that split apart the particle. It also vaporized much of the ice. The excess water vapor left in the aftermath then condensed and froze into new, smaller ice particles.
Applying this technique to clouds is “a long, long, long way in the future,” says Mary Matthews. She is a physicist at the University of Geneva and an author 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,” she says.
But tinkering with cirrus clouds could backfire if scientists aren’t careful, warns Trude Storelvmo. She is an atmospheric scientist at Yale University in New Haven, Conn. Clouds trap heat, through the greenhouse effect. So breaking up a cloud’s ice particles — which makes more of them — might actually warm Earth. The cooling tactic “could potentially work, but only if you target certain types of cirrus clouds,” she argues. It might be better to target very thick clouds only.
There also could be warming if fossil fuels are burned to power the laser, points out David Mitchell. He is an atmospheric scientist at the Desert Research Institute in Reno, Nev. When fossil fuels are burned, they produce greenhouse gases. Those gases are responsible for global warming. “I think it’s really interesting research,” he says of the new study. Still, he says, “I’m just not seeing how it’s going to make the world a cooler place.”
(for more about Power Words, click here)
atmosphere The envelope of gases surrounding Earth or another planet.
cirrus Thin, wispy clouds that usually form at elevations of 5,500 meters (18,000 feet) or more above Earth’s surface.
climate The weather conditions prevailing in an area in general or over a long period.
crystal (adj. crystalline) A solid consisting of a symmetrical, ordered, three-dimensional arrangement of atoms or molecules. It’s the organized structure taken by most minerals. Apatite, for example, forms six-sided crystals. The mineral crystals that make up rock are usually too small to be seen with the unaided eye.
fossil fuel Any fuel — such as coal, petroleum (crude oil) or natural gas — that has developed in the Earth over millions of years from the decayed remains of bacteria, plants or animals.
global warming The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.
greenhouse gas A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.
laser A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.
particle A minute amount of something.
physics The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study which emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in that field is known as a physicist.
plasma (in chemistry and physics) A gaseous state of matter in which electrons separate from the atom. A plasma includes both positively and negatively charged particles.
shock waves Tiny regions in a gas or fluid where properties of the host material change dramatically owing to the passage of some object (which could be a plane in air or merely bubbles in water). Across a shock wave, a region’s pressure, temperature and density spike briefly, and almost instantaneously.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
D. Fox. “The high life.” Science News for Students. November 28, 2012.
S. Ornes. “Dirty clouds change rainfall.” Science News for Students. Nov. 30, 2011.
A.L. Mascarelli. “Explainer: What is a laser?” Science News for Students. October 27, 2010.
A.L. Mascarelli. “A very good blast from the past: And cool new things that lasers can do.” Science News for Students. October 27, 2010.
Learn more about climate change from NASA.