NASA’s role in monitoring stratospheric ozone. Are ozone layer protection measures effective?

Abstract

The stratospheric ozone layer (10–50 km) absorbs biologically harmful ultraviolet radiation, enabling life to persist on Earth. Early NASA measurements from the 1960s–1970s showed that natural ozone levels are controlled by trace nitrogen oxides, hydrogen oxides, and halogens. Approximately 20 NASA missions, together with NOAA, ESA, and other international partners, have contributed to global ozone monitoring. Observations revealed a severe springtime ozone depletion over Antarctica in 1984–1985. NASA recorded the lowest ozone value ever measured over the South Pole—73 DU on September 30, 1994—and the largest single-day ozone hole extent of 29.9 · 10⁶ km² on September 9, 2000. The Montreal Protocol (1987) led to a 99% phase-out of regulated ozone-depleting substances. According to the latest WMO/UNEP assessment, the ozone layer is projected to return to 1980 levels by approximately 2066 over Antarctica, 2045 over the Arctic, and 2040 globally, assuming current controls remain in place. Although episodic deep ozone depletion occurred in 2023, NASA’s 2025 data show continued long-term recovery. In 2025, the minimum Antarctic ozone concentration was 147 DU on October 6, and the maximum ozone hole extent was 23 · 10⁶ km² on September 9—the largest ever recorded hole was about 30% bigger. These observations confirm that Montreal Protocol regulations are driving the gradual restoration of the ozone layer.