Researchers are looking at the idea of making the clouds above the Great Barrier Reef brighter in order to cool it down.

A team at the Sydney Institute of Marine Science is investigating marine cloud brightening to expand and brighten the clouds above the reef in a bid to cool the ocean below.

“All of our preliminary calculations so far suggest that it is plausible,” Dr Daniel Harrison, a research associate with the Ocean Technology Group at the University of Sydney, told the ABC.

“You can think about this in very layman's terms.

“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.”

The ongoing bleaching of the Great Barrier Reef is caused in large part by the warming and acidification of the water around it.

Coral reef can be restored if the environment around it is corrected, and cloud-altering is considered one of the most feasible, sensible and environmentally-safe ways to do that.

“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,” Dr Harrison said.

“Cloud brightening was conceived as a potential fallback.

“If we can't get emissions under control, maybe we can cool the entire planet by brightening the clouds.

“But nobody has thought about applying it to a small local area of a coral reef to prevent bleaching before.”

Like most geo-engineering plans, anything done to the clouds over the reef would be a temporary measure in lieu of long-term action like cutting carbon emissions.

“If we don't reduce emissions then I don't think the reef really has much chance of surviving in its current configuration at all,” Dr Harrison said.

“At the moment, we've only experienced a little bit less than 1 degree [Celsius] of average global temperature rise.

“So if you can imagine how badly this is affecting the reef now, at 1.5 or 2C the reef has no chance.

“Which is why — although we wouldn't want to have to do these geo-engineering ideas and deliberately make clouds over the reef if we didn't have to — we think we need to look into this because it might be the only way to save the reef.”