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9. The Ozone Layer and Ultraviolet Radiation
Pages 103-115

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From page 103...
... It meant that for several months of the year a hole forms in the ozone layer, which protects animals and plants from ultraviolet solar radiation. Suddenly it seemed that the chemical processes known to deplete ozone high in the earth's atmosphere were working faster and more efficiently than predicted.
From page 104...
... To gather more information about antarctic ozone chemistry and the ozone hole anct its causes, a team of scientists led by atmospheric chemist Susan Solomon, of NOAA in Boulder, Colorado, headed off in 1986 on the first National Ozone Expedition to the Antarctic. By 1987 they and other teams of researchers had learned that the ozone over Antarctica had been reduced by more than 50 percent of values recorded in 1979, the first October of satellite operation, and that at altitudes between 15 and 20 kilometers, depletion was as great as 95 percent.
From page 105...
... It is now known that in addition to the naturally occurring chemical reactions in the stratosphere, certain reactions involving chemical species of industrial origin, including chlorine and bromine, also chemically destroy ozone molecules. Atmospheric chemists F
From page 106...
... The researchers surmised that upon reaching the stratosphere, the CFCs encounter highenergy ultraviolet light, which breaks them down, releasing their chlorine atoms. The chlorine atoms can then engage with ozone in a catalytic reaction in which each chlorine fragment can destroy up to 100,000 ozone molecules before other chemical processes remove the chlorine from the atmosphere.
From page 107...
... Bromine is believed to cause 10 to 30 percent of the antarctic ozone depletion. STUDYING THE ANTARCTIC OZONE HOLE In the year before the discovery of the ozone hole, scientists were estimating that increasing use of chIorofluorocarbons might cause reductions in the total ozone at high latitudes by about one percent in the 1980s and by 5 to 10 percent 50 to 100 years from now.
From page 108...
... This information was gathered rapidly by means of aircraft and state-of-the-art instrumentation. In short order, scientists were able to measure a broad range of atmospheric compounds, including chlorine monoxide, chlorine dioxide, hydrochloric and nitric acid, nitric oxide and nitrogen dioxide, and nitrous oxide.
From page 109...
... It is within this vortex that scientists have measured such shockingly low ozone concentrations during the first two weeks of October, shortly after the beginning of the Southern Hemisphere spring. The explanation for the decrease lies in the combination of ozone-destroying chemistry and weather conditions that favor formation of the high, thin clouds known as polar stratospheric clouds (PSCs)
From page 110...
... For the most part, the hole has not spread outside of Antarctica and the lower Southern Hemisphere because it is limited by the seasons and the frigid temperatures required for the formation of the ice-laden polar stratospheric clouds. Yet, the insights gained during several years of intense data-gathering have raised concern about ozone in the stratosphere over the rest of the globe.
From page 111...
... For one, the arctic stratosphere generally warms up much earlier in the spring than does the antarctic, and the average temperatures are warmer. This means that cold temperatures and the sunlight necessary for the formation of polar stratospheric clouds and the ozone depletion they promote-overlap for a much shorter interval.
From page 112...
... Temperatures outside the polar regions are 20° to 30°C too warm for ice clouds to form, but droplets of sulfuric acid and water can support reactions involving the same chlorine reservoir compounds that deplete stratospheric ozone over the Antarctic and may help to explain part of the 3 percent ozone decrease observed over the Northern Hemisphere in the past two decades. One prospect is that sulfurous particles emitted by a large volcanic eruption could team up with chlorine compounds to accelerate ozone destruction.
From page 113...
... EFFECTS ON LIFE The ozone layer is essential to life because it shields it from damaging ultraviolet radiation. ironically, much less is known about the biological effects of increased ultraviolet radiation than about the chemical processes of ozone depletion in the atmosphere.
From page 114...
... NATIONS JOINING TO PROTECT THE OZONE LAYER The strong scientific consensus that CFCs deplete the ozone layer prompted nations to come together in unprecedented cooperation. The Montreal Protocol on Substances That Deplete the Ozone Layer, negotiated in September 1987, calls for a 50 percent reduction in CFC production from 1936 levels by 1999.
From page 115...
... As Norway's former Prime Minister and chairperson of the World Commission on Environment and Development Gro Harlem BrundtIand explains, "The scientist's chair is now firmly drawn up to the negotiating table, right next to that of the politician, the corporate manager, the lawyer, the economist, and the civic leader."


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