The Ozone Hole Discovery

The discovery of the ozone hole was announced in 1985 by a British team working on the ground with “conventional” instruments and examining its observations in detail. Only later, after reexamining the data transmitted by the TOMS instrument on NASA’s Nimbus 7 satellite, was it found that the hole had been forming for several years. Why had nobody noticed it? The reason was simple: the systems processing the TOMS data, designed in accordance with predictions derived from models, which in turn were established on the basis of what was thought to be “reasonable”, had rejected the very (“excessively”) low values observed above the Antarctic during the Southern spring. As far as the program was concerned, there must have been an operating defect in the instrument.