University:
Bradley University
Course:
ENS 307 | Science and Politics of Global Climate Change
Academic year:

2024
Views:

372

Pages:

10
Author:

Gudrunecg9m

Section 13-2  Area in the stratosphere where ozone is highly concentrated  Ozone: 3 atoms of oxygen (O3)  Absorbs most of the harmful ultraviolet (UV) radiation from the sun  Acts like a sunscreen for the Earth  Chlorofluorocarbons (CFCs)  Human-made chemicals  Nonpoisonous, nonflammable, don’t corrode metals  Became popular as coolants in refrigerators & air     conditioners and a propellant in spray cans of deodorants, insecticides, paint, etc. At Earth’s surface are chemically stable (don’t combine or break down) But CFC molecules break apart high in the stratosphere (by UV radiation) Parts of the CFC molecule destroy protective ozone A single chlorine atom from CFC can destroy 100,000 ozone molecules   Thinning of stratospheric ozone that occurs over the poles during the spring First discovered in 1985        During the dark polar winter, strong circulating winds over Antarctica isolate cold air from surrounding warmer air Air within the vortex grows extremely cold High altitude clouds made of water & nitric acid begin to form Here the products of CFCs are converted to molecular chlorine When the sunlight returns to the South Pole in spring, chlorine is split into 2 chlorine atoms by UV radiation The chlorine atoms rapidly destroy ozone Causes a thin spot which lasts for several months   Ozone is very chemically reactive Ozone produced by pollution breaks down or combines with other substances in the troposphere long before it can reach the stratosphere   UV light damages DNA Makes the body more susceptible to skin cancer  High levels of UV light can kill phytoplankton in oceans  Disrupt food chains & reduce fish harvests  Increase the amount of CO2 in the atmosphere  Especially damaging for amphibians  Lay eggs without shells in shallow water  More UV light may kill more eggs & put populations at risk   Interferes with photosynthesis Can result in lower crop yields  Montreal Protocol (then a 2nd conference in Denmark)  Group of nations agreed to eliminate most CFCs by 1995  Companies developed CFC replacements   International environmental success story Not over: CFCs remain active in the stratosphere for 60-120 years

The Ozone Shield

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