Can clouds save the Great Barrier Reef?

 By Chris Dalby

The Great Barrier Reef (GBR) may be the most high-profile victim of climate change to date…

In 2016, only 7 percent of the reef had escaped bleaching altogether. This has continued into 2017, the first time the GBR has been bleaching two years in a row. However, such a high-profile disaster also lends an opportunity to deploy innovative techniques to reverse the effects of climate change.
Media reports have been rampant that the Reef is dead, but is there any hope of still saving it? Some believe so. Publishing in Nature in March 2017, a team of scientists said that a reversal of climate change policies, as suggested by the Paris Agreement, could still reverse the damage to the Reef. Additional protection measures such as local fish protection, fighting off invasive algae, and improving water quality would go a long way.

The Sydney Institute of Marine Science is putting a team onto another idea, which seems outlandish at first glance: cloud brightening. The proposal is to send ships to seed the sky above the GBR with minuscule particles of salt. This would help larger, thicker, white clouds to form, which would in turn reflect more heat back into space and protect the GBR over the long-term. After a six-month study, the Institute is hoping this will become a real possibility.

The Sydney Institute of Marine Science in Chowder Bay (

Skepticism toward this plan has been understandable. Terry P. Hughes, leader of the initial survey that scanned the GBR for damage, said that “we didn’t expect to see this level of destruction to the Great Barrier Reef for another 30 years. In the north, I saw hundreds of reefs — literally two-thirds of the reefs were dying and are now dead.”
The impact of climate change such as warming waters was exacerbated by adverse weather patterns, such as a brutal El Niño in 2016.
Hughes’ survey not only measured the reef from the air. About 100 researchers went underwater to confirm the aerial observations by measuring the proportion of bleached corals and which were dying or already dead.
The accuracy of the aerial scores was tested by measuring in much closer proximity the proportion of corals that were bleached, and how many are either dead or dying. The 2016 survey found 55 percent of reefs surveyed were “severely bleached,” four times more than in previous surveys in 1998 and 2002. More shockingly, much of the coral found alive in March-April 2016 was dead by October-November.
This would seem to make the cloud seeding goal to save the GBR a charming but unlikely one. However, the team members are vocal about their optimism. Daniel Harrison, a postdoctoral research associate with the Ocean Technology Group at the University of Sydney, told the ABC that “all of our preliminary calculations so far suggest that it is plausible.”

Bleached branching coral (Acropora, Wikimedia)

“You can think about this in very layman’s terms,” said Harrison. “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 uses of cloud seeding are widespread around the world, going back decades. Perhaps most famously, the Chinese government shot silver iodide into the atmosphere around the capital to cause storms to form prematurely and guarantee rain would not mar the festivities of the Beijing 2008 Olympics.
Its initial application to combat climate change was first proposed by British scientist John Latham in 1990. The scientists from the Sydney Institute of Marine Science have been meeting for months and began climate modeling for the project in May.
“Cloud brightening is the only thing we’ve identified that’s scalable, sensible, and relatively environmentally benign,” says Harrison.
The hope is that, by seeding clouds to block the GBR from direct rays, the water temperature can be cooled, with Harrison believing a difference of 1-2 degrees Celsius would be enough to stop most of the bleaching.

However, cloud seeding has also a troubled track record. Following the massive use of silver iodide, areas surrounding Beijing saw freak weather patterns, such as larger than normal snowstorms.
In order to be as environmentally friendly as possible, the Sydney team is looking to marine cloud brightening (MCB), a technique which seeds clouds with “copious quantities of roughly monodisperse sub-micrometer sea water particles”, which “might significantly enhance the cloud droplet number concentration, and…possibly longevity.”
Harrison defends the technique, saying that “no chemicals are used, the droplets are very short-lived, perhaps around 24 hours, and we would only need to use the technology during periods when the corals were at high risk of bleaching.”

Colorful underwater landscape of a coral reef (Jim E Maragos, Wikimedia)

The idea has seen other incarnations. One idea to combat climate changes was to prepare a fleet of 1,500 ships, containing MCB turbines that would create a mist of seawater up to 1,000 meters up.

One promising study showed the idea was backed up. In 2013, Latham and others applied a global climate model to the problem in the Caribbean, French Polynesia and the GBR and found that “substantial increases in coral bleaching conditions…were eliminated when MCB was applied, which reduced the sea surface temperatures at these sites roughly to their original values.”
If this does prove to have merit, it will energize other similar projects around the world. The Summen Project plans to use an artificial fog, achieved through similar methods to cloud seeding, to provide additional moisture to the redwoods of California to help their photosynthesis.
Some skeptics view this as wishful thinking, a neat scientific idea that has little value in the real world. Ken Caldeira, a climate scientist from the Carnegie Department of Global Ecology, is encouraged by the research but counters that “I just don’t think there are enough clouds of the right type there that would be susceptible to marine cloud brightening.”
This is precisely what the current climate modeling stage will try to work out. Perhaps it will prove fruitless and the GBR cannot be salvaged. Theoretical models put forward by Latham and Harrison may end up not matching up to the astounding complexity of climate change factors on the GBR. But one of the most iconic natural treasures on the planet is still worth trying to save.

SEE MORE: How the UAE is making it rain by Criselda Diala-McBride

about the author
Chris Dalby
Journalist. Editor. China, Mexico, Latin America, Asia, place branding, Olympics, oil and gas, mining, renewable energy, international politics.