SIO40lecture21

SIO40lecture21 - SIO 40 Life and Climate on Earth Nov. 22...

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Unformatted text preview: SIO 40 Life and Climate on Earth Nov. 22 2010 Lecture 21 - Ozone NASA image of largest ozone hole ever over Antarctica, Sept. 2006 C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m- Ozone in the stratosphere- Ozone destruction- Formation of the Antarctic ozone hole- Montreal protocol- Trends in overall ozone loss, ozone holes- Tropospheric ozone Lecture Outline C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m Role of ozone in the stratosphere Stratospheric ozone effectively screens the Earths surface against high energy (short wavelength) UV rays. C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m Formation of the ozone layer One important consequence of the increase in atmospheric O 2 concentrations was an increase in the concentration of ozone, O 3 , in the atmosphere. Ozone is formed via the following reactions: O 2 + h O + O O + O 2 O 3 C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m Chlorofluorocarbons (CFCs) are long-lived gases used as refrigerants and in other industrial applications. When ultraviolet light waves (UV) strike CFC molecules in the upper atmosphere, a carbon-chlorine bond breaks, producing a chlorine (Cl) atom. The chlorine atom then reacts with an ozone (O 3 ) molecule breaking it apart and so destroying the ozone. This forms an ordinary oxygen molecule(O 2 ) and a chlorine monoxide (ClO) molecule. Then a free oxygen atom breaks up the chlorine monoxide. The chlorine is free to repeat the process of destroying more ozone molecules. A single CFC molecule can destroy 100,000 ozone molecules. C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m CFCl 3 + UV Light ==> CFCl 2 + Cl Cl + O 3 ==> ClO + O 2 ClO + O ==> Cl + O 2 The free chlorine atom is then free to attack another ozone molecule, and this cycle can re-occur thousands of times. Destruction of ozone by CFCs The first scientific paper about the potential for ozone destruction by CFCs was published by Sherry Rowland and Mario Molina in 1974. This paper warned about the potential for widespread ozone loss by 2050 if CFC production levels were to remain steady. C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m C lic k t o b u y N O W ! P D F- X C ha ng e V ie w e r w w w .d o cu-tr ac k .c o m For more historical perspective on the ozone hole in light of the current global warming debate, see: http://www.wunderground.com/education/ozone_skeptics.aspdebate, see: http://www....
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SIO40lecture21 - SIO 40 Life and Climate on Earth Nov. 22...

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