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Ozone depletion: Ozone depletion: MisconceptionsMisconceptions

Meteorology 10Meteorology 10De Anza College De Anza College

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How is ozone produced?How is ozone produced? Ozone is produced and destroyed naturallyOzone is produced and destroyed naturallyProduction:Production:

It is formed when oxygen absorbs solar radiation

Ozone reacts with various other chemicals, and thus is highly reactive (i.e.)

Net : O3 +O 2O2

One Cl atom can destroy ~100,000 ozone molecules

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Ozone, the good and the badOzone, the good and the bad

ozone amount

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Ozone is often confused:

Good ozone:

Bad ozone:

Stratosphere

Troposphere

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UV radiationUV radiation

What affects the amount of UV radiation hitting the Earth?

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History of Ozone DepletionHistory of Ozone DepletionChlorofluorocarbons (CFCs) developed in 1940’s and 50’s as:Chlorofluorocarbons (CFCs) developed in 1940’s and 50’s as:

1970’s CFCs detected in upper atmosphere.1970’s CFCs detected in upper atmosphere.

Many of these have long atmospheric lifetimes: Many of these have long atmospheric lifetimes:

1974 Rowland and Molina propose that CFC’s can destroy ozone 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere.in the stratosphere.CFC contain chlorine (Cl) CFC contain chlorine (Cl)

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What causes the ozone hole?What causes the ozone hole?Ozone Hole Recipe (make your own!)Ozone Hole Recipe (make your own!)

1.1. __________________________________________

2.2. __________________________________________

Formation of Polar Stratospheric Clouds (PSC’s)Formation of Polar Stratospheric Clouds (PSC’s)

3. ______________________3. ______________________

Winter Polar Vortex is region of strong winds forming an isolated Winter Polar Vortex is region of strong winds forming an isolated ‘container’ from the middle latitudes.‘container’ from the middle latitudes.This produces cold temperatures.This produces cold temperatures.Allows chemistry to develop undisturbed.Allows chemistry to develop undisturbed.

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Is the ozone hole getting much Is the ozone hole getting much bigger?bigger?

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What is being done about What is being done about ozone depletion?ozone depletion?

Montreal Protocol ~ (1988) international agreement to phase out ozone depleting chemicals

Further amendments accelerated the phase out.

Developed countries have switched to HCFC’s (more ozone friendly!)Developing countries have until 2004 to phase out CFC’s.

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Is the Montreal Protocol Is the Montreal Protocol working?working?

Seems to be…Seems to be…

Recent observations indicate that chlorine is Recent observations indicate that chlorine is beginning to decline in the atmosphere.beginning to decline in the atmosphere.

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What is the connection between ozone What is the connection between ozone depletion and global warming?depletion and global warming?

No direct connection between these environmental No direct connection between these environmental issues.issues.

Global warming produces:Global warming produces:

Tropospheric warming & stratospheric coolingTropospheric warming & stratospheric cooling Therefore, if the stratosphere cools, then ozone Therefore, if the stratosphere cools, then ozone

destroying chemistry (e.g. ozone hole), will increase. destroying chemistry (e.g. ozone hole), will increase.

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Model simulations suggest:Model simulations suggest: atmospheric chlorine will return to pre-80’s level atmospheric chlorine will return to pre-80’s level __________________ . __________________ .

Uncertainties still remain:Uncertainties still remain:

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What are predictions for the future?

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MisconceptionsMisconceptions Ozone depletion and global warming often Ozone depletion and global warming often

confusedconfused Ozone depletion – CFC’s (aerosols, refrigerants)Ozone depletion – CFC’s (aerosols, refrigerants) Global Warming – burning of fossil fuelsGlobal Warming – burning of fossil fuels

Some student ideasSome student ideas Hole in ozone hole allows more heat into atmosphereHole in ozone hole allows more heat into atmosphere Automobile exhaust responsible for ozone depletionAutomobile exhaust responsible for ozone depletion ……