"It's an insurance policy," said researcher Sudhanshu Jain.

It's called the Marine Cloud Brightening Project, and it's designed to fight global warming by making clouds over the ocean thicker and brighter so they reflect more sunlight and cool the planet.

The Sunnyvale team has reached a milestone with this high-pressure nozzle that uses salt water and looks like a normal water spray. But it took scientists a year to come up with the exact rate, flow and pressure so that the water droplets come out to the perfect size.

The salt particles are so small that in order to see them with the naked eye, you have to turn off the lights and use a laser.