Thaindian News

Washington, Feb 20 (IANS) Ships blowing off steam are helping researchers understand how man-made particles might be useful against global warming.
New results from modeling clouds like those seen in shipping lanes reveal the complex interplay between aerosols, prevailing weather and even the time of day the aerosol particles hit the air, according to new research.

“We’ve seen ship tracks affect the reflectivity of clouds,” said Phil Rasch, chief climate scientist at the Pacific Northwest National Lab in Washington.

“We decided to see how the reflectivity of clouds is influenced by particles in a very detailed model that treats clouds much more realistically than we are able to do in a typical climate model,” Rasch added.

Reflecting sunlight back into space prevents that energy from hitting Earth’s surface. So brighter clouds could have an overall cooling effect compared to darker ones.

More aerosol particles — tiny natural or man-made bits of dirt, water and gas, such as from pollution — increase the number of droplets in clouds and make each droplet smaller.

This reflects more sunlight from the surface, and the clouds appear brighter.

But the previous work revealed that some parts of the clouds above shipping lanes became brighter and other parts darker, suggesting that using aerosols to increase cloud reflectivity will be more complex than simply adding more.

“Do the brighter and darker parts cancel each other out?” asked Rasch.

To find out, the group performed some exploratory computer simulations to determine the net effect of increased aerosols.

His team simulated three ships chugging along in a 93-mile by 37-mile block of the Pacific Ocean a few hundred miles southwest of Los Angeles.

The team showed that introducing additional particles into the model near the surface — as proposed for geo-engineering — would make the clouds significantly more reflective than they would otherwise be, in certain situations.

They found that if the clouds were already drizzling then the new particles would not brighten them very effectively, said a Pacific Lab release.

Although ship tracks are helping researchers explore geo-engineering methods, the real plans won’t use polluting aerosols from ships. Instead, Rasch and others suggest that ocean vessels could spray seawater aerosols into the sky to brighten clouds.

These findings were presented at the American Association for the Advancement of Science’s annual meeting.