WEBVTT FILE 1 00:00:00.010 --> 00:00:04.030 It’s been 30 years since the UN agreed to the landmark Montreal Protocol, 2 00:00:04.030 --> 00:00:08.120 3 00:00:08.120 --> 00:00:12.310 Limiting the release of ozone-depleting substances into the atmosphere. 4 00:00:12.310 --> 00:00:16.340 5 00:00:16.340 --> 00:00:20.380 Since then, the ozone hole over Antarctica has begun to show early signs of healing. 6 00:00:20.380 --> 00:00:24.600 NASA and NOAA scientists work together to monitor the ozone layer 7 00:00:24.600 --> 00:00:28.670 8 00:00:28.670 --> 00:00:37.271 From the ground, balloons, aircraft and space.