1 Weather and Climate

Bay Area Earth Science Institute (BAESI)

Ozone depletion: Misconceptions

San Jose State University, January 24, 2004

http://www.met.sjsu.edu/baesi/

2 Weather and Climate

How is ozone produced?How is ozone produced?

Ozone is produced and destroyed naturallyOzone is produced and destroyed naturally Production: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

O2 +UV radiation O+O

O+ O2 O3

O3 + Cl ClO + O2

ClO + O Cl + O2

Ozone, the good and the bad

ozone amount

Alt

itu

de

(km

)

Ozone is often confused:

Good ozone: Stratospheric ozone The ozone layer

Bad ozone: Tropospheric ozone Smog

Stratosphere

Troposphere

7 Weather and Climate

Location (latitude)

What affects the amount of UV radiation hitting the Earth?

_______________________

_______________________

_______________________

_______________________

_______________________

UV radiation

Time of yearTime of dayCloud amountOzone amount

10 Weather and Climate

Concept MapConcept Map

11 Weather and Climate

Ozone  UV radiation  Sun  Gas  Skin Cancer  Summer  Winter  Spring  Atmosphere  CFC’s  South Pole  Trends  Ozone hole  Chlorine

 Dobson Unit  Total Ozone  Tropospheric ozone  Good ozone  Stratospheric ozone  Bad ozone  

Concept Map Terms

12 Weather and Climate

History of Ozone DepletionHistory of Ozone Depletion

Chlorofluorocarbons (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 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere.ozone in the stratosphere.

– CFC contain chlorine (Cl) CFC contain chlorine (Cl) –

Refrigerants, propellants, fire retardantsRefrigerants, propellants, fire retardants

–(10’s to 100’s of years)(10’s to 100’s of years)

Chlorine can destroy ozone rapidlyChlorine can destroy ozone rapidly

15 Weather and Climate

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.

Abundant chlorine

Cold temperatures

Sunlight to activate chemistry

17 Weather and Climate

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

No, not over the last few years

18 Weather and Climate

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.

19 Weather and Climate

Is the Montreal Protocol working?

Seems to be…

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

20 Weather and Climate

21 Weather and Climate

What is the connection between ozone depletion and global warming?

No direct connection between these environmental issues.

Global warming produces:

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

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

However: Global warming may enhance ozone depletion

22 Weather and Climate

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

__________________ .

– Uncertainties still remain: ____________________ ____________________

In next 50 years or so

Influence of global warming

Phase out of CFC’s

A slow ozone recovery should follow decreasing chlorine concentrations!!!

What are predictions for the future?

23 Weather and Climate

Ozone  UV radiation  Sun  Gas  Skin Cancer  Summer  Winter  Spring  Atmosphere  CFC’s  South Pole  Trends  Ozone hole  Chlorine

 Dobson Unit  Total Ozone  Tropospheric ozone  Good ozone  Stratospheric ozone  Bad ozone Recovery  TOMS Gas 2050 Cold temperatures Northern

Hemisphere

Concept Map Terms

Ozone

Troposphere

Atmosphere

Gas

Ozone Hole

Bad Ozone

Good Ozone

has

UV Radiation

Stratosphere

Chlorine

CFC’s

cause

is depletion of is a

is present in the

destroy

produces

present in

produce

protects the earth from

has

contain

Total Ozone

Dobson Unit

Global Warming

Skin Cancer

Sun Spring

Automobiles

is a

may cause

is the column

causes

is measurement of

25 Weather and Climate

Misconceptions

Ozone depletion and global warming often confused– Ozone depletion – CFC’s (aerosols, refrigerants)– Global Warming – burning of fossil fuels

Some student ideas– Hole in ozone hole allows more heat into

atmosphere– Automobile exhaust responsible for ozone

depletion– …