According to UK and U.S. researchers, it might be possible to fight the global warming effects associated with an increase of CO2 levels by using autonomous cloud-seeding ships to disperse salt water into the air.
The project would require the deployment of a worldwide fleet of 1,500 unmanned ships to cool the Earth even if the level of carbon dioxide doubled. These 300-ton ships ‘would be powered by the wind, but would not use conventional sails. Instead they would be fitted with a number of 20 m-high, 2.5 m-diameter cylinders known as Flettner rotors. The researchers estimate that such ships would cost between $1.3m and $3m each.
This project has been led by Professor John Latham of the National Center for Atmospheric Research in Boulder, Colorado. Latham worked with colleagues at the University of Edinburgh led by Professor Stephen Salter.
It “involves increasing the reflectivity, or “albedo”, of clouds lying about 1 km above the ocean’s surface. The idea relies on the “Twomey effect”, which says that increasing the concentration of water droplets within a cloud raises the overall surface area of the droplets and thereby enhances the cloud’s albedo. By spraying fine droplets of sea water into the air, the small particles of salt within each droplet act as new centres of condensation when they reach the clouds above, leading to a greater concentration of water droplets within each cloud.”
“These rotors would be easier to operate remotely than sails and would also serve as the conduits for the upward spray, with the spray consisting of droplets 0.8 µm in diameter generated by passing sea water through micro nozzles. The power for the spray and the cylinder rotation would be provided by oversized propellers operating as turbines. The immediate effect of seeding clouds in this way would be a local cooling of the sea surface, and as such the technique could be targeted at coral reefs, diminishing polar ice sheets or other vulnerable regions. However, the great thermal heat capacity of the ocean and the currents within it mean that these initial effects would eventually spread across the globe.”
