In one of the great environmental success stories of our time, scientists say that a 35-year-old agreement has resulted in the steady and promising recovery of the Earth's ozone layer, a critical protective shield that blocks harmful ultraviolet radiation from the sun. Dr. Paul Newman, chief scientist for Earth sciences at NASA's Goddard Space Flight Center, joins William Brangham to discuss. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders