A worldwide fleet of wind-driven autonomous ships spraying salt water into the air could counteract global warming by enhancing the reflectivity of low-lying clouds above the oceans, according to researchers in the US and UK.

The idea relies on the “Twomey effect”: increasing the concentration of water droplets within a cloud raises the overall surface area of the droplets and thereby enhances the cloud’s albedo (reflectivity), causing more reflection of solar radiation back into space. By spraying fine droplets of sea water into the air, the small particles of salt within each droplet act as new centers of condensation when they reach the clouds above, leading to a greater concentration of water droplets within each cloud.