Warming Is Getting Worse. They Just Took a First Step Toward Deflecting the Sun.

A little before 9 a.m. on Tuesday, an engineer named Matthew Gallelli crouched on the deck of a decommissioned aircraft carrier in San Francisco Bay, pulled on a pair of ear protectors, and flipped a switch.A few seconds later, a device resembling a snow maker began to rumble, then produced a great and deafening hiss. A fine mist of tiny aerosol particles shot from its mouth, traveling hundreds of feet through…