MET 112 Global Climate Change
Ozone Hole and
Human Connection
Professor Menglin Jin
San Jose State University, Department of Meteorology

1.
For regulating emissions of CFCs
2.
For limiting number of SUV sales emissions of nitrogen
3.
For limiting number of minivan sales.
4.
For regulating GHG emissions http://www.nytimes.com/2006/09/21/business/21auto.html

1.
For suing California in the first place
2.
For violating emission standards
3.
For producing autos that contribute to global warming
4.
For producing ozone depleting gases

Suggest to read:
The Ozone Hole http://www.theozonehole.com/
Basic chemistry of ozone depletion http://www.nas.nasa.gov/About/Education/Ozone/chemistry.html

Lowest value of ozone measured by TOMS each year in the ozone hole

Ozone Hole:
Ozone depletion describes two distinct, but related observations: a. a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since the late 1970s; and b. a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period .
The latter phenomenon is commonly referred to as the ozone hole
.
In addition to this well-known stratospheric ozone depletion, there are also tropospheric ozone depletion events , which occur near the surface in polar regions during spring. http://en.wikipedia.org/wiki/Ozone_depletion

Ozone
Ozone is found in boundary layer as well as in stratosphere layer.
The former is one of greenhouse gases.

Ozone Formation through Splitting of Oxygen by Ultraviolet Radiation

This figure was prepared by Robert A. Rohde

harmful UVB wavelengths (270 –315 nm) ultraviolet light (UV light)

Ozone Hole:
Reductions of up to 70% in the ozone column observed in the austral (southern hemispheric) spring over Antarctica and first reported in 1985 (Farman et al 1985)

Formation and destruction of ozone
Sunlight is the major energy source for both making and destroying stratospheric ozone:
When an Oxygen molecule absorbs a photon of light with a wavelength shorter than 200 nanometers (1 billionth of a meter) the energy splits the molecule into two Oxygen atoms. One of these atoms can react with another Oxygen molecule to form an Ozone molecule.
Up to 98% of the sun's high-energy ultraviolet light (UV-B and UV-C) are absorbed by the destruction and formation of atmospheric ozone.
The global exchange between ozone and oxygen is on the order of 300 million tons per day. http://www.nas.nasa.gov/About/Education/Ozone/chemistry.html

180
°
March 1990
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Halley
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June 1990
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September 1990

Decembe r 1990
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90 °S
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August
1990
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Septem ber
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1990
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Novem ber
1990
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October
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Octob er
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Lowest value of ozone measured by TOMS each year in the ozone hole

Global Ozone

Human activity
Climate and Weather
Climate Change
Science Understanding
Policy Maker successful example is Response to Ozone Hole

Where are the highest concentrations of ozone located?
1.
In large cities
2.
The stratosphere
3.
The troposphere
4.
Near volcanoes

Topics
 History of Ozone Depletion
 The Ozone Hole: what, where, why?
 Ozone into the future

History of Ozone Depletion: connection between human and nature
• Chlorofluorocarbons (CFCs) developed in
1940’s and 50’s as:
–
Refrigerants, propellants, fire retardants
• 1970’s CFCs detected in upper atmosphere.
– Many of these have long atmospheric lifetimes:
–(10’s to 100’s of years)
– 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere.
– CFC contain chlorine (Cl)
–
Chlorine can destroy ozone rapidly

Video: http://www.met.sjsu.edu/metr112-videos/

Ingredients:
Science interpretation
•
•
Chlorine gas
Cold Temperatures (~-80C)
Instructions:
• Chlorine gas is abundant in atmosphere due to CFC’s
• Cold Temperatures (~-80C) only occur over Antarctica during the cold winter .
•
• Allow cold temperatures to form
Polar Stratospheric Clouds (1-2 weeks).
• Allow time for polar stratospheric clouds to convert chlorine gas into ozone destroying chemicals. (1 month)
Bake ingredients with sunlight.
• Polar Stratospheric Clouds allow ozone friendly chlorine to be transformed into ozone destroying chlorine.
• Ozone depletion then starts when sun returns to Antarctica in the spring

• Montreal Protocol ~ (1988) international agreement to reduce ozone depleting chemicals
• Further amendments accelerated the phase out.
– Developed countries have switched to HCFC’s
(more ozone friendly!)
– Developing countries have until 2004/5 to phase out CFC’s.

Montreal Protocol
The Montreal Protocol on
Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion .
The treaty was opened for signature on September 16 , 1987 and entered into force on
January 1 , 1989 followed by a first meeting in
Helsinki, May 1989.

Seems to be!!!
Recent observations indicate that chlorine is beginning to decline in the atmosphere.
Kyoto protocol uses similar approach
Start off with small achievable steps
Further amendments accelerate reductions

What are predictions for the future?
• Model simulations suggest:
– atmospheric chlorine will return to pre-80’s level
__________________ .
A slow ozone recovery should follow decreasing chlorine concentrations!!!
– Uncertainties still remain:
• ____________________
• ____________________

Model Prediction for the future:
OZONE RECOVERY!

What is the connection between ozone depletion and global warming?
• No direct connection between these environmental issues.
 However: Global warming may enhance ozone depletion
• Global warming produces:
– Tropospheric warming &
– Stratospheric cooling

What is the connection between ozone depletion and global warming?
• An increase in greenhouse gases traps more heat and thus
– The stratosphere tends to cool (stratospheric cooling)
• Therefore, if the stratosphere cools, then
Ozone hole chemistry
– PSCs will likely increase
– So slightly more ozone depletion
• Global warming will delay recovery of ozone layer

Over the last 100 years, global tropospheric ozone levels have been
1.
increasing
2.
decreasing
3.
nearly constant

The chemical that triggers rapid ozone loss associated with CFCs is
1.
Carbon Dioxide
2.
Nitrogen dioxide
3.
Methane
4.
Chlorine

1.
SH Spring
2.
SH Summer
3.
NH Spring
4.
NH Summer

Global ozone values are expected to recover in the next
1.
10 years
2.
30 years
3.
50 years
4.
100 years