It

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Its not just about Global Warming

• The Problem with the Ozone Layer

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What is it?

• "The ozone layer" refers to the ozone within
  stratosphere, where over 90 of the earth's ozone
  resides.
• Ozone is an irritating, corrosive, colorless gas
  with a smell something like burning electrical
  wiring.
• Each molecule of ozone has three oxygen atoms
  (O3) and is produced when oxygen molecules (O2)
  are broken up by energetic electrons or high
  energy radiation.

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What does it do?

• The ozone layer absorbs 97-99 of the sun's high
  frequency ultraviolet light, light which is
  potentially damaging to life on earth.
• Every 1 decrease in the earths ozone shield is
  projected to increase the amount of UV light
  exposure to the lower atmosphere by 2.

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What caused the hole?

• Human activities in the last several decades have
  produced chemicals, such as chlorofluorocarbons
  (CFCs), which have been released into the
  atmosphere and have contributed to the depletion
  of this important protective layer.

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Links to Climate

• Ozone is also a greenhouse gas in the upper
  atmosphere and, therefore, plays a role in
  Earth's climate.
• Under normal conditions, the amount of
  stratospheric ozone depends on the amount of
  sunlight reaching a certain geographic area of
  the atmosphere.
• Ozone typically "builds up" to higher values over
  the poles during the winter and early spring in
  each hemisphere. Because this season is offset by
  6 months in the Northern and Southern
  hemispheres, the effect is seen at the North and
  South poles roughly 6 months apart.

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How fast is it expanding?

• the "ozone hole" is where lower than normal
  levels of ozone have been detected.
• it is formed and destroyed by chemical reactions
  that require light.
• So the ozone hole is more intense when there is
  sunlight over the south pole then where then is
  darkness.
• Human activities have made the hole much more
  intense, but as far as we know there was always a
  lower amount of ozone over the south pole (and to
  a lesser extent over the north pole too) before
  human activities altered the composition of the
  atmosphere.
• the ozone layer has also thinned in the temperate
  and tropical zones on Earth

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An Anthropogenic Issue!

• The data showed conclusively that human-produced
  trace gases that contain chlorine and bromine
  were causing the ozone hole.
• The Global Monitoring Division of ESRL has
  monitored the yearly Antarctic ozone hole from
  the South Pole station and measuring total column
  ozone from a ground based Dobson
  spectrophotometer since 1963, and since 1986 by
  launching balloons.

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Driven by Temperatures
The ozone hole closes up in winter but
intensifies in the summer

• View of the Antarctic Ozone hole
• (July thru December)

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Arctic Ozone Hole

• http//earthobservatory.nasa.gov/Newsroom/NasaNews
  /ReleaseImages/20031210/07a_ozone2000.mpeg
• Not as pronounced as the Antarctic Ozone Hole,
  although does show up. (Blue regions indicate low
  ozone levels)

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Arctic Ozone Problem?

• Significant depletion also occurs in the Arctic
  ozone layer during the late winter and spring
  period (January - April). However, the maximum
  depletion is generally less severe than that
  observed in the Antarctic, with no large and
  recurrent ozone hole taking place in the Arctic.

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Why is a hole in the atmosphere an issue?

• If there is a hole in the ozone layer then this
  means that more harmful ultra-violet rays get
  through than are good for us or many other life
  forms, plant or animal.

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Too much ultra-violet light can result in

• Eye damage such as cataracts
• Immune system damage
• Reduction in phytoplankton in the oceans that
  forms the basis of all marine food chains
  including those in Antarctica.
• Damage to the DNA in various life-forms So far
  this has been as observed  in Antarctic ice-fish
  that lack pigments to shield them from the
  ultra-violet light (they've never needed them
  before)
• Skin cancer

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ozone-depleting gases

• These gases contain chlorine and bromine atoms,
  which are known to be harmful to the ozone layer
• CFCs hydrochlorofluorocarbons (HCFCs),
• human-produced gases once used in almost all
  refrigeration and air conditioning systems
• Methyl bromide,
• Primarily used as an agricultural fumigant
• Nitrous Oxides,
• oxidation of ammonia (NH3) primarily from
  farming
• Also a result of burning fossil fuels

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Global warming and the ozone hole is there a
connection?

• The ozone hole is a completely different
  phenomenon to global warming, however there are
  links between them.  The ozone hole is caused by
  ozone depleting chemicals in the atmosphere,
  which have been produced by industry, for example
  CFCs. 

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Global warming and the ozone hole is there a
connection?

• 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 stratospheric clouds can form.  This makes
  a larger area susceptible to ozone depletion and
  provides another link between the two issues.