CFC’s and the Ozone Layer
Are there holes?
- Measuring ozone holes: In 1984 the problem of ozone depletion was first detected. Researchers in Antarctica noticed thinning in the spring and early summer (September –December).
- It is more a ‘thinning’ than a hole. In some areas, there was a decrease of more than 50%.
- In 1999, the hole was at its largest.
- Between 1999-2000 (winter) there was a depletion of 65% compared to about 45% the previous winter.
- Ozone loss is expected to decrease (due to the banning of gases which damage the layer) until around 2050. This will equal the 1975 level.
- It will take 100-200 years for full recovery to pre-1950 levels.
- Ozone levels are measured using satellites. U.V. thickness is measured in Dobson Units (DU). Visit the following webpage to see ozone levels in recent months. For a comparison, tropical ozone levels are between 250-300 DU throughout the year.
- Click here for more information on Dobson Units
Ozone holes or thinning areas –are they dangerous?
Ozone holes or thinning areas have a number of effects:
Causes of damage to the ozone layer.
- The main cause of ozone depletion is the release of a group of gases known as CFC’s (chlorofluorocarbons).
- These are used as refrigerator coolants, in aerosols and expanded plastics.
- The gas is man-made, inert and harmless to humans.
- These gases slowly rise into the upper atmosphere (they may take many years to do this, so have a delayed effect), where they react with ozone.
- CFC’s rise into the upper atmosphere
- Chlorine is released when the CFC breaks down
- Cl + O3 form CLO and O2
- CLO + O form CL and O2
- O3 is now depleted and CL is free to cause further decay of O3
- High flying jets release sulphuric acid droplets which act as nuclei for chlorine and other pollutants which then destroy ozone.
Plugging the hole – the future
- There are a number of ways to reduce ozone depletion and there has been considerable success since the holes were first discovered in 1984.
- Ban the use of CFC’s – The Montreal Protocol
- Produce jet aircraft fuel with a lower sulphur content.
- Find safe alternatives to CFC’s.