Ozone Depletion <ul><li>You should know and understand; </li></ul><ul><li>What is ozone, where does it occur and why is it...
What is ozone, where does it occur and why is it important? <ul><li>Ozone is trioxygen (O 3 ) </li></ul><ul><li>Ozone is f...
The difference between good and bad ozone <ul><li>The ozone is the stratosphere is GOOD ozone as it filters the UV radiati...
Ozone Depletion <ul><li>Ozone is continually created and destroyed within the stratosphere (O+O 2 =O 3 +O=2O 2 +O=O 3  etc...
The Ozone Hole <ul><li>Whilst CFCs and other ODS led to a depleltion in global stratospheric ozone levels this was not dis...
Ozone depletion over Antartica
The largest Antarctic   ozone hole ever recorded (Sept 2006)
The Impacts of Ozone Depletion <ul><li>Less ozone = more UV penetration into the troposphere and lower atmosphere </li></u...
1989 Montreal Protocol <ul><li>This is a good example of a successful international treaty to tackle a climatic hazard iss...
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7.75 - Ozone Depletion

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7.75 - Ozone Depletion

  1. 1. Ozone Depletion <ul><li>You should know and understand; </li></ul><ul><li>What is ozone, where does it occur and why is it important? </li></ul><ul><li>The difference between good and bad ozone </li></ul><ul><li>How human pollutants affect levels of stratospheric ozone leading to ozone depletion and the “ozone hole” </li></ul><ul><li>The impact of ozone depletion on plants and animals </li></ul><ul><li>How international treaties have addressed the ozone issue </li></ul>
  2. 2. What is ozone, where does it occur and why is it important? <ul><li>Ozone is trioxygen (O 3 ) </li></ul><ul><li>Ozone is found in both the troposphere (lower atmosphere) and the stratosphere </li></ul><ul><li>In the stratosphere the ozone forms a “layer”, this layer is important as it protects us from UV radiation – ozone is responsible for filtering a very high percentage of UV radiation </li></ul>
  3. 3. The difference between good and bad ozone <ul><li>The ozone is the stratosphere is GOOD ozone as it filters the UV radiation </li></ul><ul><li>Ground level tropospheric ozone is BAD ozone as it can exacerbate asthma and cause other respiratory and associated health problems </li></ul><ul><li>When you investigate urban microclimates and pollution you will study ground level ozone </li></ul>
  4. 4. Ozone Depletion <ul><li>Ozone is continually created and destroyed within the stratosphere (O+O 2 =O 3 +O=2O 2 +O=O 3 etc.) </li></ul><ul><li>The total amount of ozone in the stratosphere is determined by the balance between photochemical production and recombination </li></ul><ul><li>This good ozone in the stratosphere can be destroyed by ozone depleting substances (ODS) </li></ul><ul><li>ODS include chlorofluorocarbons (CFCs), hydro-chlorofluorocarbons (HCFCs) and halons – these have anthropogenic sources such as coolants in air conditioning systems and propellants in aerosol sprays. </li></ul><ul><li>Whilst the source of much of the worlds ODS has been removed (see Montreal Protocol below) it is worth remembering that 1 chlorine atom can destroy 100,000 molecules of ozone and these chlorine atoms stay in the stratosphere a long time. </li></ul>
  5. 5. The Ozone Hole <ul><li>Whilst CFCs and other ODS led to a depleltion in global stratospheric ozone levels this was not distributed evenly. </li></ul><ul><li>In the tropics no noticeable declines have been recorded, whilst in middle latitudes declines of between 3 and 6% have been measured. </li></ul><ul><li>Reactions that take place in polar stratospheric clouds speed up the depletion of ozone – thus levels of depletion of Antarctica (where such clouds are common) were much faster than elsewhere. </li></ul><ul><li>This is where the concept of an “ozone hole” first emegred </li></ul>
  6. 6. Ozone depletion over Antartica
  7. 7. The largest Antarctic ozone hole ever recorded (Sept 2006)
  8. 8. The Impacts of Ozone Depletion <ul><li>Less ozone = more UV penetration into the troposphere and lower atmosphere </li></ul><ul><li>The most serious human impacts are skin cancer and cataracts </li></ul><ul><li>Increased tropospheric UV radiation can lead to greater levels of BAD tropospheric ozone </li></ul><ul><li>High levels of UV can also affect rice and plankton growth </li></ul>
  9. 9. 1989 Montreal Protocol <ul><li>This is a good example of a successful international treaty to tackle a climatic hazard issue </li></ul><ul><li>It has undergone 7 revisions since it was first ratified in 1989 </li></ul><ul><li>Levels of CFCs and other ODS have declined </li></ul><ul><li>Even with these success it will be 2050 before the ozone layer will have fully recovered </li></ul>
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