Professor Menglin JinSan Jose State University, Department of Meteorology

MET 112 Global Climate Change

Ozone Hole and Human Connection

Why are automakers suing Why are automakers suing California?California?

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

Why is California suing Why is California suing automakersautomakers

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/

http://www.nas.nasa.gov/About/Education/Ozone/chemistry.html

Basic chemistry of ozone depletion

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

Vertical Layers of the Lower Vertical Layers of the Lower AtmosphereAtmosphere

Ozone

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

videovideo

• http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/ozone%20hole%20and%20human%20connection/

• Ozone sequence since 1979

Ozone Formation through Splitting Ozone Formation through Splitting of Oxygen by Ultraviolet Radiationof Oxygen by Ultraviolet Radiation

Absorption of Ultraviolet Absorption of Ultraviolet Radiation by OzoneRadiation by Ozone

This figure was prepared by Robert A. Rohde

ultraviolet light (UV light)

harmful UVB wavelengths (270–315 nm)

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 ozoneSunlight is the major energy source for both making and destroying stratospheric ozone:                                                                                               

When an Oxygen molecule absorbs a photon of light with a wavelength shorterthan 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

Dobson U

nits

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March 1990

Halley Bay

Total Ozone Content from Total Ozone Content from Nimbus 7 TOMSNimbus 7 TOMS

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June 1990

Total Ozone Content from Total Ozone Content from Nimbus 7 TOMSNimbus 7 TOMS

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September 1990

Total Ozone Content from Total Ozone Content from Nimbus 7 TOMSNimbus 7 TOMS

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325

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December 1990

Total Ozone Content from Total Ozone Content from Nimbus 7 TOMSNimbus 7 TOMS

August 1990

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October 1990

November 1990

Total Nimbus 7 TOMS Ozone Total Nimbus 7 TOMS Ozone Content from Content from

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October 1979

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October 1982

October 1985

October 1988

Total Ozone Content from Total Ozone Content from Nimbus 7 TOMSNimbus 7 TOMS

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 Makersuccessful example is Response to Ozone Hole

Where are the highest Where are the highest concentrations of ozone located?concentrations of ozone located?

1. In large cities

2. The stratosphere

3. The troposphere

4. Near volcanoes

Ozone Depletion

TopicsTopics History of Ozone DepletionHistory of Ozone Depletion The Ozone Hole: what, where, why?The Ozone Hole: what, where, why? Ozone into the futureOzone into the future

Early concerns of ozone Early concerns of ozone depletion depletion

History of Ozone Depletion: connection History of Ozone Depletion: connection between human and naturebetween human and nature

• Chlorofluorocarbons (CFCs) developed in Chlorofluorocarbons (CFCs) developed in 1940’s and 50’s as: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 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere.can destroy 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

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

videovideo

• http://www.met.sjsu.edu/metr112-videos/MET%20112%20Video%20Library-MP4/ozone%20hole%20and%20human%20connection/

• Ozone-1.mp4

Ozone Hole RecipeOzone Hole RecipeIngredients:Ingredients:

• Chlorine gasChlorine gas• Cold Temperatures (~-80C)Cold Temperatures (~-80C)

Instructions:Instructions:

• Allow cold temperatures to form Allow cold temperatures to form Polar Stratospheric Clouds (1-2 Polar Stratospheric Clouds (1-2 weeks).weeks).

• Allow time for polar stratospheric Allow time for polar stratospheric clouds to convert chlorine gas into clouds to convert chlorine gas into ozone destroying chemicals. (1 ozone destroying chemicals. (1 month)month)

• Bake ingredients with sunlight.Bake ingredients with sunlight.

• bingo, a delicious ozone hole!bingo, a delicious ozone hole!

Science interpretationScience interpretation

• Chlorine gas is abundant in Chlorine gas is abundant in atmosphere due to CFC’satmosphere due to CFC’s

• Cold Temperatures (~-80C) only Cold Temperatures (~-80C) only occur overoccur over Antarctica Antarctica during the during the cold wintercold winter..

• Polar Stratospheric Clouds allow Polar Stratospheric Clouds allow ozone friendly chlorine to be ozone friendly chlorine to be transformed into ozone destroying transformed into ozone destroying chlorine. chlorine.

• Ozone depletion then starts when Ozone depletion then starts when sun returnssun returns to Antarctica in the to Antarctica in the springspring

• Ozone hole grows from late August Ozone hole grows from late August through till October. through till October.

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

• 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.

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.

Montreal Protocol

Is the Is the Montreal ProtocolMontreal Protocol working?working?

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

• 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?

Model Prediction for the future:

OZONE RECOVERY!

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

warming?warming?• No direct connection between these

environmental issues.

• Global warming produces:

– Tropospheric warming & – Stratospheric cooling

However: Global warming may enhance ozone depletion

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

warming?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 Over the last 100 years, global tropospheric ozone levels have beentropospheric ozone levels have been

1. increasing

2. decreasing

3. nearly constant

The chemical that triggers rapid ozone The chemical that triggers rapid ozone loss associated with CFCs isloss associated with CFCs is

1. Carbon Dioxide

2. Nitrogen dioxide

3. Methane

4. Chlorine

The Antarctic ozone hole The Antarctic ozone hole develops duringdevelops during

1. SH Spring

2. SH Summer

3. NH Spring

4. NH Summer

Global ozone values are expected to Global ozone values are expected to recover in the nextrecover in the next

1. 10 years

2. 30 years

3. 50 years

4. 100 years

Antarctic Ozone HoleAntarctic Ozone Hole

• Ozone hole begins to develop in spring when the sun returns to Antarctica

• Occurs between (August-November)

• First detected by scientist in 1985 and has continued to increase in the years of observation

• Not technically a “hole”, but a diminishing or thinning of the ozone layer

Function & Characteristics Function & Characteristics • Absorb UV radiation

– UV-a, UV-b, UV-c– UV-b high energy 95%

absorbed

• Upper stratosphere• Composed of O3

• Measured in Dobson Units– Conc. of O3 molecules

• 2.6x1016 molecules per sq.cm

• Average thickness– 300 DU or 3mm thick– 100 DU or 1mm thick

Causes of DepletionCauses of Depletion• Chlorofluorocarbon (CFC) • Presence of UV, Chlorine

dissociates from (CFC’s)– Produces chlorine radicals– Decompose ozone molecules

• Polar stratospheric clouds– Occur in winter at -80 °C– CFC reacts with nitric acid to

liberate chlorine– Other factors:

• Methyl bromide • Aerosols & refrigerants• Agricultural pesticides

The Polar Vortex EffectThe Polar Vortex Effect

• Large scale cyclone centered at poles• Ozone depletion causes cooling of 6°C in

stratosphere• Intensifies westerly winds and prevents outflow of

cold air• Results in:

– Cooler temperatures in the eastern region and warmer temperatures at the Antarctic Peninsula (Larsen, Ross, Wilkins, Ice Shelf's)

– Promotes accelerated warming and increase in sea ice

Past EventsPast Events

• Deepest ozone hole:– September 30, 1994– Levels fell to 73 DU

• Largest ozone hole:– September 1, 2006– 10.6 million sq. miles– Antarctica

• (5.4 million sq. miles)

Effects of Ozone DepletionEffects of Ozone Depletion

• Increased surface warming

• Promotes increased melting– Potential to increase sea levels

• Affects marine ecosystems– Increased UV will result in less phytoplankton – Building block of oceanic food chain– Adverse effects on other species