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

Making the low-lying clouds off the north-east coast larger and more reflective could cool the waters below and help to stem the widespread coral bleaching that is occurring with growing intensity across vast swathes of the 2415km reserve.

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

"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," he told ABC News.

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 Harrison to explore the scheme. The scientists have been meeting for the past 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.