DEPLETION OF OZONE LAYER.

I read in the local newspaper in the morning today about the loss of Ozone layer to the extent of 40% (as reported by a WMO study) and was shocked about it. I thought it to be too large and wanted to check up a bit more about it.

After going through the available matter on the web I found that the layer has indeed gone down by 40% due to the very cold winter this year. Generally the decrease is around 30% in the winters.

Ozone is an allotrope (Forms of a chemical element with different physical and chemical properties) of Oxygen and is called O 3.

It is present mostly in the Stratosphere about 10 to 50 Km above us and filters the ultraviolet rays that are emitted by the Sun to the extent of some 97-99% . The ultraviolet rays of high frequency are extremely harmful for living beings. The Ozone layer itself varies in thickness geographically as well as with change in seasons.

The following factors affect the Ozone layer:

1. Volcanoes: Although volcanoes put in significant amount of sulfate aerosols into the atmosphere, these get rained off to the earth due to the high content of water vapor in volcanic eruptions. Large volcanic eruptions certainly disturb the ozone layer but their effect on the layer is around 3% and lasts not more than 3 years.

2. Stratospheric Winds: These winds change directions every 26 months known as QBO. As a result the ozone layer gets disturbed region to region but there is no net ozone loss overall.

3. Sunspot Cycle: Ozone is created by Solar Ultraviolet radiation. As there is a change in the activity of the Sun every 11 years, the level of Ozone also changes but this is less than 2%. However, large solar storms and flares may affect the ozone layer more. This also gets corrected in a period of 11 years.

4. Chlorine in the Stratosphere: This is man made and is operative because of the use of Fluorocarbons (used as refrigerant gases). This was estimated to be around 3% per decade. This is the one effect on the ozone layer which is irreversible and is permanent.

In the US and the European Economic Community, the use of fluorocarbons has been totally phased out now. Realizing the danger they have moved over to other less harmful gases.

Developing countries have also signed the Montreal protocol which is for the protection of the Ozone layer and are phasing out the use of these dangerous ozone depleting gases.

It would however take a long time for the harmful emissions already made before the phasing out by the developed nations.

A study conducted by scientists in the year 2003 has indicated that the rate of depletion of the ozone layer is slowing down due to the decrease in the use of fluorocarbons. This is a welcome sign and all can heave at least small sigh of relief.