NASA satellite observations have provided the first evidence that the rate of ozone depletion in the Earth’s upper atmosphere is decreasing. This may indicate the first stage of ozone layer recovery.
From an analysis of ozone observations from NASA’s first and second Stratospheric Aerosol and Gas Experiment (SAGE) and its Halogen Occultation Experiment (HALOE) satellite-based instruments, scientists have found less ozone depletion in the upper stratosphere (at an altitude of 22-28 miles) after 1997.
SAGE I was launched on the Applications Explorer Mission-B spacecraft in 1979, while the Earth Radiation Budget Satellite carried SAGE II into orbit in 1984. The Space Shuttle ‘Discovery’ carried HALOE into space on the Upper Atmosphere Research Satellite in 1991.
This decrease in the rate of ozone depletion is consistent with the decline in the atmospheric abundance of man-made chorine and bromine-containing chemicals that have been documented by satellite, balloon, aircraft and ground based measurements.
Concerns about ozone depletion in the upper atmosphere or stratosphere led to ratification of the Montreal Protocol on Substances that Deplete the Ozone Layer by the international community in 1987. The protocol restricts the manufacture and use of human-made, ozone-depleting compounds, such as chlorofluorocarbons and halons.