Ozone Depletion and the Ozone Hole Preview Stratospheric sunscreen tropospheric pollutant 60 s 70 s theories suggested depletion mechanisms 1985 discovery of ozone was a big surprise lead to increased research effort Chlorine and PSC hypothesized as cause lead to international restrictions and bans 80 s 90 s ozone hole continued to expand and midlatitude loss continues Present growth slowed although 2003 was big Chlorine concentrations stabilizing CFC s eliminated Ozone as natural sunscreen Average Ozone Column 1978 1993 Stratospheric Ozone Brief Historical Perspective 1881 Hartley first hypothesized the presence of ozone lab 1924 Dobson invented spectrophotometer of measure ozone 1929 Gotz using Dobson s instrument found that ozone was in the stratosphere 25 km 1930 Chapman developed theory of stratospheric ozone origin 1949 Brewer role of circulation in controlling ozone layer Catalytic cycles Hydrogen Hunt 1966 NOx from tropospheric N2O Crutzen 1970 NOx from aircraft Johnston 1971 CFCs Molina Rowland 1974 1985 Farman discovers the ozone hole over Antarctica 1986 Solomon McElroy unravel the role of polar stratospheric clouds and halogen catalysis Regulation of CFC production Montreal Protocol 1987 London Agreement 1990 Copenhagen amendment 1992 Jeagle 2004 Measurements made by balloon ozonesondes before and after intense depletion October average ozone concentrations Jeagle 2004 Regulations on the production of CFCs Vienna convention 1985 Convention for the Protection of the ozone layer signed by 20 nations research future protocols Montreal Protocol 1987 Protocol on substances that deplete the ozone layer Ratified in 1989 Legally binding controls freezing production to 1985 levels London Amendment 1990 Phaseout of production by 2000 for developed nations and by 2010 for developing nations Copenhagen Agreement 1992 Phaseout for developed nations by 1996 The Montreal Protocol is Working Without the Montreal Protocol ozone depletion in 2050 would be at least 50 at midlatitudes in the Northern Hemisphere and 70 at midlatitudes in the Southern Hemisphere about 10 times larger than today Surface UV B radiation in 2050 would at least double at midlatitudes in the Northern Hemisphere and quadruple at midlatitudes in the Southern Hemisphere compared with an unperturbed atmosphere This compares to the current increases of 5 and 8 in the Northern and Southern Hemispheres respectively since 1980 WMO 1998 Scientific Assessment of Ozone Depletion
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