Marine Cloud Brightening

Aerial view from plan of ocean
cloud making machine

Giving coral reefs a fighting chance in a warming climate

Our world-leading Marine Cloud Brightening (MCB) program is pioneering a new way to help coral reefs withstand a warming climate.

This innovative technique builds on a natural process by spraying a fine mist of seawater into the air using specialised cannons. As the mist rises, sea salt particles interact with low-lying ocean clouds, making them brighter and more reflective.

Brighter clouds send more sunlight back into space, reducing the amount of heat that reaches the ocean below.

By increasing the reflectivity of low-lying marine clouds, Marine Cloud Brightening aims to lower water temperatures, reduce stress on fragile marine ecosystems, and help protect coral reefs from the impacts of climate change and bleaching events.

How Marine Cloud Brightening Works

Diagram of ocean clouds boat droplets and reef
Marine Cloud Brightening process

Coral reefs in crisis

Our oceans are vulnerable

The oceans absorb about 90% of the excess heat trapped by global warming.

Bleaching on the rise

Heat and intense sunlight stress corals, leading to bleaching. Bleaching events in the Great Barrier Reef are becoming more frequent and severe, with six major events occurring in the past 10 years.

The clock is ticking

Roughly the size of Italy, the Great Barrier Reef is approaching a critical climate threshold. At 1.5°C of global warming, risks to coral reefs increase sharply; at 2°C the projected losses are far greater.

Coral

Last year out here, we conducted a proof-of-concept experiment where we showed that it’s technically feasible to pump seawater and atomize it into trillions per second of tiny little seawater droplets, which in theory can go on to help brighten clouds and cool the reef.

This year, what we’re really interested in is looking at the behaviour of that plume of sea-salt droplets as it drifts away from the boat. There are a few critical questions around that: how many of those droplets make it up to cloud height, and how do atmospheric turbulence and winds spread those droplets? These questions will help us design a system for the future that may be able to work over the whole reef.

This fieldwork mission has several components. One component is collecting background atmospheric data. We have a whole lab set up on the ship that samples air from the front of the boat—capturing the wind before it hits the vessel—and we’re analysing all the background properties of particles that are naturally floating around in the air out here on the reef.

Another part, further back on the ship, is the cloud-brightening prototype. That’s Mark 2 this year, and it’s producing around twice as many droplets as last year. We’re very interested in how those droplets are spreading through the atmosphere, so there’s a big focus this year on using drones as sampling platforms to measure the plume—not just horizontally, but also vertically.

One of the great advances we’ve made from last year is really in our sampling platforms. The boat we’re using for downwind sampling is now larger and much more capable, and we’re actually able to launch and retrieve drones from it.

As well as being important to the Indigenous people of Australia, we recognise the reef is important to all Australians. We love the coast, we love our water—so let’s look after it together.

Cloud brightening is just one of a whole suite of ideas we’re examining in the Reef Restoration and Adaptation Program. The overarching goal of all this research is to explore every possible way we can help the reef survive climate change.

World-first innovation

Southern Cross University is leading the world’s first outdoor Marine Cloud Brightening experiments, advancing research to help protect coral reefs from extreme marine heat.

Led by Associate Professor Daniel Harrison and his team at the National Marine Science Centre, the program brings together expertise in atmospheric science, engineering, climate modelling, and environmental monitoring to test whether Marine Cloud Brightening can safely reduce ocean temperatures during periods of heat stress.

This is not just a concept study. Southern Cross University’s team has now delivered six consecutive field experiments, marking a major step forward in understanding how Marine Cloud Brightening performs outside the laboratory and under real-world marine conditions.

Using an end-to-end research approach – from cloud physics and modelling to laboratory development, field deployment, and environmental monitoring – the team is generating the evidence needed to assess the feasibility, effectiveness, and risks of this emerging climate intervention.

Initial experiments have focused on the Great Barrier Reef, where rising ocean temperatures are placing increasing pressure on one of the world’s most important and vulnerable ecosystems.

This work is helping determine whether Marine Cloud Brightening could one day contribute to reef protection at scale, while positioning Southern Cross University at the forefront of global climate intervention research.

Making headlines around the world

Manmade clouds that could help save the Great Barrier Reef

New York Times Magazine

underwater large corals and tropical fish

Can artificially altered clouds save the Great Barrier Reef?

Nature

mist out the back of boat in the ocea

Blocking out the sun

Australian Financial Review - Tech Zero

Sun with blue sky and cannon

Artificial cooling 'urgent' for Great Barrier Reef after warming spike

New Scientist

Coral at Lizard Island

Could cloud brightening slow impact of coral bleaching?

Channel 4 News

Clouds against blue sky

Could ‘marine cloud brightening’ reduce coral bleaching on the Great Barrier Reef?

The Conversation

Aerial view from plane of bright blue coral reef

Shielding the reef

100 Climate Conversations

Spray jets from a large cannon shooting out

Failure to communicate: Geoengineering to fight climate change

Science

SCU research vessel seeding clouds at the Great Barrier Reef

The leading force

Associate Professor Daniel Harrison is an engineer and oceanographer with experience spanning marine science, fisheries management, and ecosystem modelling.

He has led the MCB project at Southern Cross University since 2020 and is passionate about protecting one of the world’s most precious ecosystems, the Great Barrier Reef.

His research focuses on how engineered interventions in marine systems can improve environmental and ecological outcomes. 

Man smiling with beach in background

“We are no longer in a world where conservation is best achieved by simply leaving ecosystems alone.  Marine Cloud Brightening offers hope and is inspired by a natural process. Our team's aim is to give coral reefs a fighting chance. ”

Associate Professor Daniel Harrison Southern Cross University
Researcher profile

Large group of people in high vis workwear smiling at camera on board a large boat

Partners

The program works closely with national and international research partners, as well as Traditional Owners, regulators, regional stakeholders and industry, ensuring the research is scientifically rigorous, transparent and socially responsible. 

CSIRO Queensland University of Technology University of New South Wales Freie Universitat Berlin University of Melbourne

Watch the journey

A scientist outside the National Marine Science Centre

Cloud brightening equipment

The latest cloud brightening generator (V model) in action

Diver swimming above coral reef

What's next

  • Improve spray technology to create finer sea salt particles using less energy, making reef-scale use possible.
  • Test both upgraded current systems and explore new spray methods for the future.

  • Use data from the past six years of field trials to better predict how clouds respond and how effective the approach can be.
  • Run the largest field trials to date, using multiple vessels operating at the same time.

  • Expand monitoring to better understand environmental impacts and ensure safety.
  • Establish three permanent monitoring stations along the Great Barrier Reef.
  • Develop new ways to track results using aircraft, satellites and advanced data analysis.

The team will also continue working closely with Traditional Owners, communities and regulators to ensure the research is responsible, transparent and supported.

The team is ready to continue this critical research to help cool reef systems, reduce coral bleaching and give reefs a better chance of survival.

The ability to reach these goals depends on future funding support.

Discover more research

Reefs and Oceans Impact Cluster
Catchments, Coasts and Communities Impact Cluster
Coral IVF

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