Ozone gas (O3) in the upper atmosphere shields Earth from the Sun's dangerous ultraviolet radiation. Since the early 1980's, scientists have been aware that human-made chlorofluorocarbons (CFC's) and other chemicals destroy atmospheric ozone worldwide. The greatest losses have occurred at the poles. Over the Antarctic region, a distinct ozone "hole" emerges in late September or early October. The 2010 Antarctic ozone hole reached its maximum extent on September 26—about 20 million km2, an area twice the size of the United States. Although the size of the annual ozone hole has varied relatively little in the last decade, global ozone levels are slowly recovering due to the international ban on CFC's initiated by the Montreal Protocol in 1987.The United States satellite measurement program for ozone, run jointly by the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA), has measured Earth's ozone distribution since 1978. This visualization shows false-color ozone measurements in both ultraviolet and infrared wavelengths obtained by the SBUV/2 and HIRS instruments aboard the NOAA Polar Operational Environmental Satellite system. The 1980 and 1987 October averages are from NASA's Total Ozone Mapping Spectrometer sensor aboard NASA's Nimbus-7 satellite. Ozone levels are shown in measurements of Dobson units. The ozone hole represents ozone levels lower than 220 Dobson units. The projections of the size of future ozone holes are based on the work of NASA's Paul A. Newman and colleagues.
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