A UK-based team of scientists is working to understand how firing a mist of fine salt water high into the sky may be able to brighten clouds enough to reflect more sunlight back into space and help keep parts of the world cooler amid rising global temperatures.
If successful, the concept, known as marine cloud brightening or marine sky brightening, could one day help protect fragile ecosystems in specific locations, such as the Great Barrier Reef, from extreme heatwaves.
At the University of Manchester, the research team, led by Professor Hugh Coe, is running experiments inside a three‑storey stainless‑steel cloud chamber to test whether their mists of seawater can brighten clouds enough to effectively reflect more sunlight back into space, with potential real-world trials of the technique on the cards for 2028.
"We’ve got a pretty good handle that the physics work," Professor Coe told The Times.
The work is being carried out as part of the REFLECT project, funded by the UK’s Advanced Research and Invention Agency (ARIA) through its Exploring Climate Cooling programme. It is just one of 22 geoengineering schemes for which ARIA has earmarked £57m.
The initiative is aiming to build the independent evidence required to assess whether emerging climate cooling approaches such as this kind of geo-engineering could ever work and if the techniques which emerge are safe or governable.
Despite the new approach, the researchers have stressed that the need for humans to slash greenhouse gas emissions remains essential.
“Decarbonisation is the only sustainable route out of the climate crisis,” Mark Symes, ARIA’s programme director told The Independent.
“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.
He added: "ARIA’s Exploring Climate Cooling programme is providing the objective evidence base the world needs to make safe, informed decisions about these proposed interventions.”
The urgency to protect the planet from the worst effects of the climate crisis, along with the potential profits which apparently effective solutions could generate are among the key factors driving interest in temporary cooling techniques.
Already, venture capital‑backed companies have moved into this space, which currently lacks any governance framework. As a result it is argued that publicly-funded research is needed to establish what is possible – and what is not.
The REFLECT project team told The Independent they are currently researching precisely how droplets behave in their cloud chamber in Manchester, building bespoke sprayers, and using computer modelling, while also beginning the process of reaching out to "stakeholders" in coastal communities which could potentially host future trials.
No site has been chosen to date and no outdoor experiments are due to take place before 2028, they said, and even then they must pass ARIA’s independent oversight, safety assessments and community co‑design requirements.
ARIA was created in 2022 by Dominic Cummings and inspired by America's DARPA – the R&D agency behind the internet, GPS, and personal computing. It has a mandate for taking a “high‑risk, high‑reward” approach to encourage scientific breakthroughs and has attracted cross‑party support. The Conservatives gave the agency an initial £800m budget, and in 2025, Labour committed £1.2bn over four years, rising to £400m a year by 2030.
The REFLECT team said one of the key challenges for them to overcome is the lack of real‑world data on how best to generate 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 any potential field trials.
Any outdoor tests would be small‑scale, time‑limited and tightly monitored, using only seawater and replicating natural sea‑spray processes, they said. Initial trials, if approved, would involve short bursts of mist released over the sea, with effects dissipating within 24-hours.
The goal, the team said, is to build a responsible and transparent framework for evaluating whether techniques like marine cloud brightening could ever play a role in managing extreme heat as our planet warms, and to ensure that any future decisions are grounded in rigorous scientific evidence.
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