the ozone hole is a completely different phenomenon to global warming! there are links between them
TRANSCRIPT
The ozone hole is a completely different phenomenon to global warming!There are links between them.
Links between Global Warming and Climate Change
Summary: The ozone hole is caused by ozone depleting chemicals in the atmosphere, which have been produced by industry, for example CFCs.
• One link is that CFCs are also 'greenhouse
gasses'. Enhanced global warming is a probable consequence of increasing amounts of 'greenhouse gasses', such as carbon dioxide and methane, in the atmosphere.
• Although the surface of the earth warms, higher up the atmosphere cools, thus increasing the area where polar stratospheric clouds can form. This makes a larger area susceptible to ozone depletion and provides another link between the two issues.
Ozone
Ozone LossCentral Questions & Key Concepts
1. Ozone depletion and global warming are two very different things!
2. How are human activities affecting the ozone layer?
3. What can humans do about changes in the ozone layer?
Ozone• A form of oxygen in which three
atoms of oxygen occur together.• Produced in photochemical reactions
involving sunlight, nitrogen oxides, hydrocarbons, and diatomic oxygen.
• Chemically active and has a short average lifetime in the atmosphere.
• Forms a natural layer high in the atmosphere that protects us from harmful ultraviolet radiation from the sun.
• A pollutant when present in the lower atmosphere.
Ultraviolet Radiation and Ozone• Ozone Shield: Stratospheric ozone layer that absorbs
ultraviolet radiation
Movie - Take notes!
Measurement of Stratospheric Ozone• Dobson Unit (DU)
– Commonly used to measure the concentration of ozone.
Production of Ozone in the Stratosphere
A. photo dissociation of diatomic oxygen
B. Two single oxygen atoms
C. single oxygen atom combines
with O2
D. Ozone is produced
Average Antarctic Minimum Ozone Concentration (1990-2005)
Why is There Seasonal Thinning of Ozone over the Anatarctic?
• 1984- researchers discovered 40-50% of ozone in upper stratosphere over Antarctica was being destroyed
• 1987- “smoking gun”- – CFC’s primarily cause of ozone thinning – Polar vortex- huge swirling mass of very cold air that
is isolated from the rest of the atmosphere until the sun returns a month later
Polar Stratospheric Clouds • Polar Stratospheric Clouds (PSCs)
– Ozone destroying clouds that form in the stratosphere during the polar winter
– Chlorine Nitrate (cl catalyzes ozone destruction)(ClONO2)
– Nitric acid (HNO3)
TAKE NOTES!
Average Change in Concentration of Stratospheric Ozone (1970-2002) by Latitude
• Ozone reduction varies most in the Antarctic– Highest concentrations of
O3 are found here naturally
• Concentrations at the equator are nearly constant.– Lowest concentrations are
found at the equator
Size of the Antarctic Ozone Hole
This graph above shows the minimum Ozone (measured in Dobson units) detected over the Antarctic. It shows that ozone levels have been decreasing over the last two decades.
The Ozone hole has, in general, been increasing in size over the last two decades. At times the Ozone hole has extended over 25 million square kilometers, an area one hundred times larger than the United Kingdom and equivalent to one sixth of the total world land mass.
Ozone Depleting Chemicals• Chlorofluorocarbons (CFCs)
• Halons
• Methyl bromide
• Carbon tetrachloride
• Methyl chloroform
• Hydrogen chloride
“...use of CFCs increases rapidly...”
Ozone Depletion and CFCs
• Ozone depleted due to emission of CFCs
• CFCs are stable and have a long residence time in the atmosphere
• In stratosphere, release chlorine and enter into catalytic chain reaction- depletes ozone
• More UV radiation reaches lower atmosphere “Scientists discover a link
between CFCs and ozone layer depletion.”
Why Should We Be Worried about Ozone Depletion?
Reasons for Concern
• Less Ozone Causes: – Immune system suppression– Increase in acid deposition– Lower crop yields and decline in
productivity“If the ozone layer depletes, more
harmful UV-B radiation will reach the earth through the damaged ozone
layer.”
Why Should We Be Worried… Life in the Ultraviolet Zone
• Less Ozone Also Causes: – increased incidence and
severity of sunburn – more cataracts – more skin cancer
• More About Skin Cancer & Cataracts – increasing in Australia, New Zealand, South
Africa, Argentina & Chile because the ozone layer is thin several months a year in those places
“More UV-B radiation means more skin cancers,more diseases and eye cataracts, less yield from plants, less productivity from oceans, damage to plastics...”
Management Issues
• Key issue is whether ozone depletion is natural or human-induced
• Montreal Protocol
• Collection and Reuse of CFCs
• Substitutes for CFCs– HFCs and HCFCs
• Short-Term Adaptation to Ozone Depletion
Solutions: Protecting the Ozone Layer
• Montreal Protocol– Treaty created in 1987 by 36 nations – Says- cut emissions of CFC’s into
the atmosphere by about 35% between 1989 & 2000
– Met 3 more times – Met in 1997 in Montreal – Adopted a protocol accelerating the phase out of key
ozone depleting chemicals – CFC production fell by 85%
• Other Legislation/Meetings (see handout)
Solutions: Protecting the Ozone Layer
• Stop producing all ozone depleting substances
• CFC substitutes
– HCFC’s- contain fewer chlorine atoms per molecule than CFC’s
– HFC’s- contain Fluorine but no chlorine
– HC’s- hydrocarbons - useful as coolants & insulating foam in refrigerators
Solutions: Protecting the Ozone Layer
• Technofixes – Physicist Alfred Wong- each year wants to
launch blimps 20-30 football-fields long.
– Blimps are radio-controlled and would contain electrical wires that would inject negatively charged electrons to the stratosphere when exposed to high voltages (see article)
– Others suggest using lasers to blast CFC’s out/ but no one knows how it will affect climate, birds, or planes
Will the International Treaty to Slow Ozone Depletion Work?
• still a black-market of CFC’s
• some countries cheating
• prevention is the best way to deal with global environmental problems
What Can You Do?
"Do not release CFCs - recycle them!”
“Demand ozone friendly products.”