Lecture 21

Lecture 21 - SIO 40 – Life and Climate on Earth Nov 20 th 2009 Lecture 21 Ozone NASA image of largest ozone hole ever over Antarctica Sept 2006

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Unformatted text preview: SIO 40 – Life and Climate on Earth Nov. 20 th 2009 Lecture 21 - Ozone NASA image of largest ozone hole ever over Antarctica, Sept. 2006- 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 Role of ozone in the stratosphere Stratospheric ozone effectively screens the Earth’s surface against high energy (short wavelength) UV rays. 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 υ → O + O O + O 2 → O 3 hlorofluorocarbons (CFCs) are long-lived gases used as refrigerants and in other industrial applications. hen ultraviolet light waves (UV) strike CFC molecules in the upper atmosphere, a carbon-chlorine bond reaks, producing a chlorine (Cl) atom. The chlorine atom then reacts with an ozone (O 3 ) molecule reaking it apart and so destroying the ozone. This forms an ordinary oxygen molecule(O 2 ) and a chlorine onoxide (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 zone molecules. 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. For more historical perspective on the ozone hole in light of the current global warming debate, see: http://www.wunderground.com/education/ozone_skeptics.asp Skepticism and the Ozone Hole fter the landmark publication of Rowland and Molina, industry spokespeople and scientists mployed by conservative think tanks launched a campaign to dis-credit the idea that CFC’s ould be damaging to ozone. The following tactics were employed:- Public relations campaigns were launched to dispute evidence- Dire economic consequences were predicted due to reducing CFC production; potential cost benefits were ignored- Respected scientists were paid to argue against the CFC-ozone threat- Non-peer reviewed publications were used to support the industry point of view- Scientific uncertainty was stressed, as was the certainty of economic loss- Data was distorted to support industry views- Scientists and environmentalists were disparaged as being either out to get grant money, or unnecessarily alarmist- Claims were made that reducing CFC production would put the US at a disadvantage relative to other nations- Claims were made that more research was needed before taking action...
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This note was uploaded on 10/23/2010 for the course SIO SIO 40 taught by Professor Barbeau during the Fall '10 term at UCSD.

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Lecture 21 - SIO 40 – Life and Climate on Earth Nov 20 th 2009 Lecture 21 Ozone NASA image of largest ozone hole ever over Antarctica Sept 2006

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