NASA Earth Observatory Programs

Climate Change, Anthropocene, & Associated Issues

Date posted: 10/27/15

NASA's World Observatory website presents a plethora of earth-imaging programs designed to measure the climatological conditions. The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which damages DNA in plants and animals (including humans) and leads to skin cancer. Prior to 1979, scientists had not observed concentrations below 220 Dobson Units. But in the early 1980s, through a combination of ground-based and satellite measurements, scientists began to realize that Earth natural sunscreen was thinning dramatically over the South Pole each spring. This large, thin spot in the ozone layer came to be known as the ozone hole. This series of images shows the size and shape of the ozone hole each year from 1979 through 2015 (no data are available for 1995). The measurements were made by NASA Total Ozone Mapping Spectrometer (TOMS) instruments from 1979 to 2003 and by the Royal Netherlands Meteorological Institute (KNMI) Ozone Monitoring Instrument (OMI) from 2004 to present. Purple and dark blue areas are part of the ozone hole. As the images show, the word hole is not literal - no place is empty of ozone. Scientists use the word hole as a metaphor for the area in which ozone concentrations drop below the historical threshold of 220 Dobson Units. Using this metaphor, they can describe the hole size and depth. These maps show the state of the ozone hole each year on the day of maximum depth - the day the lowest ozone concentrations were measured. The series begins in 1979. The maximum depth of the hole that year was 194 Dobson Units (DU) - not far below the historical low. For several years, the minimum concentrations stayed in the 190s, but beginning in 1983, the minimums got deeper rapidly: 173 DU in 1982, 154 in 1983, 124 in 1985. In 1991, a new threshold was passed; ozone concentration fell below 100 DU for the first time. .