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Change in the clouds

SCU research vessel seeding clouds at the Great Barrier Reef


25 May 2023

As Australia’s Great Barrier Reef continues to suffer in the era of climate change, could there be hope in the clouds? At Southern Cross University, Dr Daniel Harrison’s ‘cloud brightening’ technology offers innovative and promising potential for an environmental treasure.

Man smiling with beach in background

Change in the clouds

On clear days, when the sky is that unique Australian blue and the ocean is glass, Dr Daniel Harrison reckons there is no better place in the world than being at the controls of his four-seater Piper Warrior light aircraft. Following a flight plan that traces the Coffs Coast and then takes him out to sea, Daniel views from up high what is happening in the sea below.

There was a time when Daniel had ambitions to be a career pilot, which seems in contrast to what he does now as an oceanographer, engineer, researcher and Senior Lecturer at Southern Cross. However, consider the projects that he is either leading or in which he is closely involved, and the separation of sky and sea is not so marked.

At the heart of everything is a unifying purpose – protection of Australia’s Great Barrier Reef – where the concept of transforming tomorrow is imbued with massive energy and urgency.

A major player in this mission is the $150m Reef Restoration and Adaptation Program (RRAP), a collaboration between several Australian universities – including Southern Cross University – as well as the Australian Institute of Marine Science (AIMS), the CSIRO, Great Barrier Reef Foundation and the Federal Government. Daniel’s scientific team is investigating cooling and shading options for the Reef, including the use of cloud brightening technology, floating reflective surface films, and creating sea fog. “When it comes to the Great Barrier Reef, we have a window of opportunity that is rapidly closing,” says Daniel. “But if some of these ideas work as well as we hope, our modelling suggests it might be enough to alter the trajectory of the Reef and help it transition through this difficult period. There’s such a large amount of warming that’s already locked into the climate system that we need to see really strong action now.”

Cloud brightening is the strong action earning greatest attention. It involves the pumping of atomised sea water into the air above the Reef. As each tiny droplet evaporates, just three per cent – give or take – is crystallised salt. Each salt crystal then has a chance to become the nucleus for a cloud droplet.

“We’re not actually creating clouds,” explains Daniel. “When the cloud forms, there’s a given amount of water content and each droplet needs a nucleus to condense around. If we provide more of these cloud condensation nuclei, the same cloud reflects more sunlight, thereby deflecting solar energy away from reef waters when heat stress is at its maximum.”

It was off the coast of Townsville in 2020 that Daniel led the world’s first outdoor trial of cloud brightening technology to combat coral bleaching. “At the time, the Great Barrier Reef had gone through three mass bleaching events in just five years,” says Daniel. “Corals were bleaching all around us while we conducted our tests. It really emphasised the extent of the problem and how little time we have. Reef bleaching has occurred again during 2022 and we were one of the first groups to raise the alarm with the Great Barrier Reef Marine Protection Authority.

Along with Daniel and the Southern Cross University National Marine Science Centre, researchers from the Sydney Institute of Marine Science, the University of Sydney and Queensland University of Technology were involved in testing prototype equipment developed in partnership with Italian company EmiControls.

“Using drone technology linked to a sampling vessel, it showed how we can successfully create hundreds of trillions of these sea salt crystals per second which then float up into the atmosphere to bolster the reflectivity of existing clouds,” says Daniel.

“If the technology proves successful and could be expanded and applied over the Great Barrier Reef – a massive upscaling from the proof of concept type processes based research the group is now undertaking – it could reduce the severity of coral bleaching during marine heatwaves by cooling and shading the corals below.”

Daniel says the benefits of cloud brightening are environmental and economic. As well as protecting against coral bleaching in a relatively cost-effective way, it also just might buy enough time for longer-term climate change mitigation to lower ecosystem stress.

“The coral used to have such vibrancy, such colour. It’s such a treasure and we run the risk of losing it.”

Talk of treasure provides an ideal segue for one of the impetuses of Daniel’s scientific career, although it means going back 600 years or so.

To explain, between 1405-1433, China sent hundreds of treasure-laden ships and tens of thousands of men to extend imperial and trade control over the Indian Ocean and beyond. In charge was Zheng He, an extraordinary figure in history who went from court eunuch one day to fleet admiral the next.

But that’s another story. Suffice to say that much speculation exists about Zheng’s voyages, including the contention that he sailed to America decades before Columbus and to Australia centuries before the Dutch, French and British.

Jump forward six centuries and you find the younger Daniel Harrison as a University of Sydney engineering undergraduate engaged during his Honours project developing a novel underwater sonar: “My role was to examine silt and mud to determine the efficacy of technology in finding evidence of shipwrecks. Having read about Zheng He, engineering and oceanography came together for me. It just made sense. I suppose that is what set me on my career path.”

That path brought Daniel to the Southern Cross University National Marine Science Centre in 2019. Before that, career highlights included two years as a Visiting Scholar at the University of Southern California, Senior Research Fellow at the Sydney Institute of Marine Science, and recipient of the prestigious Myer Innovation Fellowship.

The Fellowship was to develop the concept of using solar radiation management approaches for bleaching protection on the Great Barrier Reef.

“These concepts and research are exciting, but they are driven by a far greater need,” says Daniel. “When you see the Great Barrier Reef, what you see is loss. That is alarming because humans are terrible at seeing the big picture and we forget so quickly what we have lost. Add the impact of pollutants, plastics, fishing and other stressors, and I wonder what I can show of the Reef to my young sons as they grow.

“Even if cloud brightening works, it can still only buy us time. Unless the world shifts from its current path and prioritises green energy and carbon dioxide removal of some of our pollution already in the atmosphere, then the long-term future of the Reef looks bleak.

“It will take a marathon effort to save it. Blue sky thinking for a blue water environment. But is there a choice? I don’t believe so.”