A £57million-valued fund for a controversial scheme aimed at "dimming the Sun" and slowing global warming has been given the green light.
The Advanced Research and Invention Agency (Aria) will fund 21 projects, including five outdoor trials, expected to begin in 2027.
These experiments will test methods to manipulate Earth's climate by reflecting sunlight away from our planet.
Techniques include injecting aerosols into the atmosphere and "brightening clouds" to combat rising global temperatures.
One of the approaches being tested is Marine Cloud Brightening, which involves ships spraying saltwater into the sky.
This process enhances the reflectivity of low-lying clouds by forcing water droplets to come together - making them more reflective.
Aria will fund 21 projects, including five outdoor trials, expected to begin in 2027
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Professor Mark Symes, Aria's programme director, said: "You may indeed not be able to see any effect from the ground at all, but you should be able to measure it using equipment that flies through the cloud."
Indoor tests will be conducted before outdoor trials begin in winter 2027-2028 at as-yet-undecided locations.
Another University of Cambridge-led project receiving funding is Stratospheric Aerosol Injection.
This involves releasing tiny particles, typically sulphur dioxide, into the stratosphere using planes to reflect sunlight away from Earth.
Scientists at Yale University have already proposed using this approach at the north and south poles to reverse ice loss.
And similar experiments have already taken place elsewhere - in March 2023, scientists launched a high-altitude weather balloon which released sulphur dioxide into the stratosphere.
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Cambridge University professor Mike Hulme has warned that Aria is leading the world down a 'slippery slope'
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In high levels, sulphur dioxide can lead to serious health problems - including damage to airways and lungs.
And some scientists have raised serious concerns about the "climate manipulation" tech.
Mike Hulme, a professor of human geography at the University of Cambridge, warned that Aria is leading the world down a "slippery slope".
"£57m is a huge amount of taxpayers' money to be spent on this assortment of speculative technologies intended to manipulate the Earth's climate," he told the Telegraph.
Prof Hulme has also warned of 'unwanted side-effects' behind the scheme
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"Just because they 'work' in a model, or at a micro-scale in the lab or the sky, does not mean they will cool the climate safely, without unwanted side-effects, in the real world."
Prof Hulme further cautioned: "There is therefore no way that this research can demonstrate that the technologies are safe, successful or reversible."
And Dr Naomi Vaughan, professor of climate change at the University of East Anglia, warned that sunlight reflecting methods could create a "new risk" to society.
Potential unintended consequences of these technologies include regional droughts, crop failures and shifts to the Atlantic jet stream - the latter of which could drag hurricanes and tropical diseases northward.
