How coral of Great Barrier Reef could be saved by big, bright clouds

Scientists in Australia are examining the possibility of enlarging and brightening the clouds around the Great Barrier Reef to save the delicate coral reefs from bleaching.

Making the low-lying clouds off the coast of north-east Australia larger and more reflective would potentially cool the waters below and help to stem the widespread coral bleaching that is occurring with growing intensity across vast swathes of the 1,500-mile stretch of reefs.

Daniel Harrison, a postdoctoral research associate at the University of Sydney, said preliminary testing indicated that cloud brightening was a “plausible” solution.

“You can think about this in very layman's terms,” he told ABC News.

“If you're in a hot sunny day and a cloud comes across overhead, you can feel right away there's quite a lot less heat coming through.”

Cloud brightening was first proposed as a way to address global warming by British physicist John Latham in a short article in the journal Nature almost 30 years ago.

He proposed deploying fleets of ships to spray tiny particles of salt at low-lying clouds above the ocean. The particles would cause additional droplets to form, producing larger, denser and whiter clouds, which would reflect more heat back into space.

Australian scientists at The Sydney Institute of Marine Science believe cloud brightening could prove to be the most feasible  and “environmentally benign” way to try to save the reef. The institute has awarded a fellowship to Dr Harrison to explore the scheme. The scientists have been meeting for the last six months to discuss the options.

“If we can make just a little bit less heat over the reef for a few months during say an El Nino year, when it's at most risk of getting bleached, we should be able to cool the water a degree or two, which is enough to prevent most of the damage,“ he said. “All of our preliminary calculations so far suggest that it is plausible.”

He explored other options, including pumping cool water onto the reef when temperatures got too high, but concluded that the cloud brightening scheme was the best approach.

Scientists last month released research which found widespread damage to coral in the Great Barrier Reef, with about two-thirds of the famous marine reserve suffering bleaching.

The surveys showed consecutive years of mass bleaching for the first time – a worrying development because the coral needs several years of normal ocean temperatures to recover.

Dr Harrison said this would be the first time the approach would be applied to a small area.

“If we can’t get emissions under control, maybe we can cool the entire planet by brightening the clouds,” he added.

Researchers in America are investigating whether a similar scheme could help preserve redwood trees. “If we could artificially produce fog on summer mornings, and that could help us buy the redwoods more time as we shift to a less carbon-intensive economy, that’s potentially a good thing,” Elliott Campbell of the University of California told MIT Technology Review.

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