Inspired by maritime observations, this geoengineering technique would try to expand the coverage of the long clouds left by the passage of ocean freighters on the open water. An aerosol of sea salt particles and seawater vapor would be injected into these existing clouds, which would then expand and shade our oceans. The director of the Chemical Sciences Division of NOAA’s Earth System Research Laboratory received a $4 million grant from Congress and permission to study these sea salt vapors. Meanwhile scientists at the University of Washington are working on increasing the whiteness and brightness of clouds by spraying trillions of particles of seawater into the clouds above the ocean, brightening them. The team’s early computer models predict that if just 15% of marine clouds were brightened by 5% to 7%, it could offset warming by 2 to 3 degrees. Swiss scientists, meanwhile, are developing ways to eliminate cirrus clouds, those thin, wispy clouds made from ice crystals that form at high altitude and trap heat in the atmosphere. Other efforts include painting the roofs of large groups of houses white and laying reflective sheets in deserts.