Ozone Hole over the Antarctic

Context :

  • During September and October, the ozone hole over the Antarctic has been the smallest observed since 1982, NASA and US National Oceanic and Atmospheric Administration (NOAA) scientists have reported.

About Ozone layer

  • The ozone layer resides in the stratosphere and surrounds the entire Earth.
  • UV-B radiation (280- to 315- nanometer (nm) wavelength) from the Sun is partially absorbed in this layer. As a result, the amount of UV-B reaching Earth’s surface is greatly reduced. UV-A (315- to 400-nm wavelength) and other solar radiation are not strongly absorbed by the ozone layer.
  • Human exposure to UV-B increases the risk of skin cancer, cataracts, and a suppressed immune system. UV-B exposure can also damage terrestrial plant life, single cell organisms, and aquatic ecosystems.
  • The ozone “hole” is really a reduction in concentrations of ozone high above the earth in the stratosphere. The ozone hole is defined geographically as the area wherein the total ozone amount is less than 220 Dobson Units.
  •  Man-made chlorines, primarily chloroflourobcarbons (CFCs), contribute to the thinning of the ozone layer
  • Manufactured chemicals deplete the ozone layer. Each spring over Antarctica (it is now spring there), atmospheric ozone is destroyed by chemical processes. This creates the ozone hole, which occurs because of special meteorological and chemical conditions that exist in that region.
  • Ozone is also created close to the surface as a byproduct of pollution can trigger health problems such as asthma and bronchitis.

Why its small this year?

  • There have been abnormal weather patterns in the atmosphere over Antarctica. In warmer temperatures like this year, fewer polar stratospheric clouds form and they don’t persist as long, limiting the ozone-depletion process.
  • NASA has cautioned it is important to recognise that what we are seeing this year is not a sign that atmospheric ozone is suddenly on a fast track to recovery.

About Montreal Protocol

  • The Montreal Protocol on Substances that Deplete the Ozone Layer is the landmark multilateral environmental agreement that regulates the production and consumption of nearly 100 man-made chemicals referred to as ozone depleting substances (ODS).
  • When released to the atmosphere, those chemicals damage the stratospheric ozone layer, Earth’s protective shield that protects humans and the environment from harmful levels of ultraviolet radiation from the sun.

Source: IE