You would probably have heard about a "hole" in the ozone layer over Antarctica, where the damage to the ozone layer is the worst. This hole is two times the size of China, or some 30,000 times the size of Singapore!

When we speak of a "hole" in the ozone layer, we do not mean an actual physical hole. Rather, it means a significant reduction in ozone concentration.

Most of the products that release ozone-harming chemicals are used in places that are more developed and where more people live in. The climate in the Antarctic makes it practically inhabitable. Temperatures go as low as 50 – 70 degrees Celsius below freezing point.

The amount of CFCs released into the atmosphere is high in the Northern Hemisphere, where most of the world’s population resides. Products containing CFCs and other harmful chemicals are definitely used more widely in the North.

Therefore, theoretically speaking, the damage to the ozone layer should be worst where more CFCs are released into the atmosphere.

What causes the "hole" in the Ozone Layer?

Even though ozone-harming chemicals released may not be as high over the Antarctic as over the Northern Hemisphere, these chemicals get mixed throughout the atmosphere, no matter where they are released.

But why is the damage to the ozone layer worst over the Antarctic?

There are actually two different types of ozone depletion processes.

The first type is known as homogeneous depletion. It is caused by the chemistry reactions as different gases mix together. Homogeneous ozone depletion is the cause of the reduction of global ozone levels. The thinning of the ozone layer found over Europe and the United States are examples of this form of ozone depletion.

The second type of ozone depletion chemistry, which occurs over the Antarctic, is known as heterogeneous depletion.

Heterogeneous ozone depletion is caused by reactions on the surfaces of ice particles, which has resulted in significant damage to the ozone layer over the Antarctic each spring. It is caused by the mixture of ozone-harming chemicals released into the atmosphere, with the unique climate of the South Pole.

CFCs releases chlorine into the air. During the winter months, this polluted air forms clouds and ice crystals. When spring comes, and the sun appears, the chlorine in these clouds and ice particles turn into chlorine monoxide, and sets off a rapid string of reactions. In just a few weeks, as much as 70% of the ozone levels in the lower stratosphere over the Antarctic is destroyed.

Part 1: Introduction
Part 3: Can we save the Ozone Layer?