UK scientists are working on a novel geoengineering technique that involves firing a fine mist of salt water high into the sky to brighten clouds and reflect more sunlight back into space, potentially helping to cool parts of the planet amid rising global temperatures.
Marine Cloud Brightening Research
The concept, known as marine cloud brightening or marine sky brightening, could one day protect fragile ecosystems such as the Great Barrier Reef from extreme heatwaves. At the University of Manchester, a team led by Professor Hugh Coe is conducting experiments inside a three-storey stainless-steel cloud chamber to test whether seawater mists can effectively brighten clouds. Real-world trials are being considered for 2028.
"We've got a pretty good handle that the physics work," Professor Coe told The Times.
The REFLECT Project
The research is part of the REFLECT project, funded by the UK's Advanced Research and Invention Agency (ARIA) through its Exploring Climate Cooling programme. ARIA has allocated £57 million to 22 geoengineering schemes, aiming to build independent evidence to assess whether such climate cooling approaches are viable, safe, and governable.
Despite the new approach, researchers stress that reducing greenhouse gas emissions remains essential. "Decarbonisation is the only sustainable route out of the climate crisis," said Mark Symes, ARIA's programme director. "However, decarbonisation is not happening quickly enough to protect many parts of the world from the worst effects of global heating. Current debates around climate cooling are paralysed by a lack of objective data."
Urgency and Governance
The urgency to combat climate change, along with potential profits from effective solutions, has driven interest in temporary cooling techniques. Venture capital-backed companies have entered this space, which currently lacks governance. Publicly funded research is needed to establish what is possible and what is not.
The REFLECT team is researching droplet behaviour in the cloud chamber, building bespoke sprayers, using computer modelling, and engaging with coastal communities that could host future trials. No site has been chosen, and no outdoor experiments are expected before 2028. Any field tests must pass ARIA's independent oversight, safety assessments, and community co-design requirements.
ARIA's Role
ARIA was created in 2022, inspired by America's DARPA, with a mandate for high-risk, high-reward scientific breakthroughs. It has cross-party support, with an initial £800 million budget from the Conservatives and £1.2 billion committed by Labour over four years, rising to £400 million annually by 2030.
Key challenges include the lack of real-world data on generating consistent water droplet sizes. Over the next three years, researchers will test different spraying methods, compare results with predictive models, and work with local groups to shape potential field trials. Any outdoor tests would be small-scale, time-limited, and tightly monitored, using only seawater and replicating natural sea-spray processes. Initial trials would involve short bursts of mist over the sea, with effects dissipating within 24 hours.
The goal is to build a responsible and transparent framework for evaluating whether marine cloud brightening could play a role in managing extreme heat, ensuring decisions are grounded in rigorous scientific evidence.
