Marine Cloud Brightening is a reversible geoengineering method proposed to mitigate rising global temperatures. It relies on propelling a fine mist of salt particles high into the atmosphere to increase the albedo of clouds – the amount of sunlight they reflect back into space. This would then reduce temperatures on the surface, as less sunlight reaches the Earth.
Clouds form when water droplets gather on dust or other particles in the air. Increasing the amount of salt particles in the atmosphere allows more of these water droplets to form, making the clouds denser and therefore more reflective.
A new paper, published in the journal Philosophical Transactions of the Royal Society A, has looked at four different ways of getting the particles into the sky, to compare how effective they may be. The researchers found that a technique called the ‘Rayleigh Jet’ proved to be best.
Named after Lord Rayleigh, who provided the theory, the technique relies on spraying a fine jet of water that breaks down into small droplets into the sky. The liquid droplets evaporate quickly, leaving behind just the salt particles.
These particles, say the paper’s authors, could be generated from specially built ships that could travel the world’s oceans spraying salt particles into the air where they then hang in the atmosphere for several days until they return to Earth as rain.
Previous studies have optimised the size of the salt particles needed to produce the best increase in cloud reflectance but haven’t taken into account how much energy the technique would need and how much it would cost to operate. More…