Ozone Layer and Its Depletion

Overview of the Ozone Layer

• Located 15 to 35 kilometers above Earth's surface.
• Surrounds the planet as a barrier against ultraviolet (UV) radiation from the sun.

Composition and Function

• Part of the stratosphere (second layer of Earth's atmosphere).
• Composed of ozone, a highly reactive molecule with three oxygen atoms.
• Trace gas with about 3 molecules of ozone per 10 million air molecules.
• Absorbs about 98% of harmful UV light, acting as Earth's sunscreen.

Causes of Ozone Layer Depletion

• Thinning of the ozone layer due to pollution.
• Chlorofluorocarbons (CFCs):
  • Primary cause of ozone breakdown.
  • Composed of carbon, chlorine, and fluorine.
  • Found in refrigerants, aerosols, and plastic products.
  • When exposed to UV rays, break down to release chlorine.
  • Chlorine reacts with ozone, breaking it apart.

Ozone Layer Damage

• Often referred to as 'ozone holes,' but more accurately thin patches.
• Thinnest in polar regions, especially over Antarctica.
  • Low temperatures accelerate CFC conversion to ozone-damaging chlorine.

Global Impact and Recovery

• About 90% of CFC emissions from industrialized countries in the northern hemisphere.
• Montreal Protocol (1989):
  • Banned the production of ozone-depleting substances.
  • Resulted in falling levels of chlorine and other harmful elements.

Future of the Ozone Layer

• Scientists predict a return to natural chlorine levels in approximately 50 years.
• The Antarctic ozone hole expected to shrink to less than 8 million square miles.