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The ozone hole refers to annual, temporary reductions in the polar regions, where much larger losses in ozone occur each spring - up to 70% over Antarctica or 30% over the Arctic -- followed by recovery in the summer. This reduction is held by a wide scientific consensus to be due primarily to an increase in concentrations of stratospheric chlorine from breakdown of human manufactured CFC emissions. Ozone depletion varies geographically and by season.
Since the ozone layer prevents most harmful wavelengths of ultraviolet light from passing through the earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern and led to speedy adoption of the Montreal Protocol banning CFC use.
In public policy discussions, the term ozone layer depletion is considered synonymous with the theory that a trend of global ozone depletion, which is caused by CFC emissions, is subsequently allowing more ultraviolet radiation to reach the earth's surface. It is suspected that a variety of biological consequences, including, for example, increases in melanoma and the destruction of plankton populations in the ocean's photic zone, may result from this increased UV exposure.
In 1970 Prof. Paul Crutzen pointed out the possibility that nitrogen oxides from fertilizerFertilizers are chemicals given to plants with the intention of promoting growth; they are usually applied either via the soil or by foliar spraying. Fertilizers typically provide, in varying proportions, the three major plant nutrients ( nitrogen, phosphs and supersonicAny speed over the speed of sound, which is approximately 343 m/s or 761 mph or 1,225 km/h at sea level, is said to be supersonic . Many modern fighter aircraft are supersonic. The Concorde was a supersonic passenger aircraft, but, since its final retirem aircraftThis article refers to the tool of travel. There is a separate article about the movie Airplane An aircraft is any machine capable of atmospheric flight. Categories and clasification Aircraft fall into two broad categories: Heavier than air Heavier than a might deplete the ozone layer. In 19741974 is a common year starting on Tuesday (click on link for calendar). Events January-February January 5 Dungeons & Dragons officially released. February 4 Patricia Hearst, the 19 year old granddaughter of publisher William Randolph Hearst, is kidnapped Frank Sherwood RowlandFrank Sherwood Rowland (born June 28, 1927) is a Nobel laureate and a professor of chemistry at the University of California, Irvine. His research is in atmospheric chemistry and chemical kinetics. Born in Delaware, Ohio, Rowland received his B. from Ohio and Mario J. MolinaMolina (born March 19, 1943) was awarded the 1995 Nobel Prize in Chemistry for his role in elucidating the threat to the Earth's ozone layer of chlorofluorocarbon gases (or CFCs). This Nobel Prize was shared with Paul J. Crutzen of UCSD and F. Sherwood Ro realised that when CFCs finally break apart in the atmosphere and release chlorine atoms they cause ozone depletion. These three scientists received the Nobel Prize in Chemistry in 1995 for this work. They calculated that if CFC production continued to increase at the going rate of 10%/year until 1990, then remain steady, CFCs would cause a global 5 to 7 percent ozone loss by 1995 and 30-50% loss by 2050. However, the discovery of the Antarctic "ozone hole" by Farman, Gardiner and Shanklin (announced in a paper in Nature in May 1985) was a surprise - chemical reactions on PSCs in the cold Antarctic stratosphere caused faster depletion than expected - and caused worldwide publicity. Satellite measurements showing massive depletion of ozone around the south pole were becoming available at the same time. However, these were initially rejected as unreasonable by data quality control algorithms; the ozone hole was only detected in satellite data when the raw data was reprocessed following evidence of an ozone hole in in situ observations.
Ozone depletion has been observed all over the globe but is greatest at high latitudes (that is, near the poles). The best known example is the annual thinning of the ozone layer over Antarctica during the polar spring (see ozone hole section below).
Since 1981 the UNEP has sponsored a series of reports on scientific assessment of ozone depletion. The most recent is from 2002.
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