Over the past few years, news regarding Antarctica has been dominated by the depleting Ozone layer and it potential harmful effects on human life through ratiation levels of UV from the Sun. In the beginning of September 2000, the American space organisation NASA announced that the hole in the ozone layer was bigger than ever before, reaching 28.3 square kilometres over Antarctica. This chapter explains what the ozone layer exactly means, what caused the hole in this protective layer and what for the consequences this has.
What is ozone?
Ozone is a toxic, strong reactive compound consisting of three oxygen atoms. The word is derived from the Greek word ozein, what means ‘to smell’. Not without a reason because the gas has a terrible odour. The chemical formula is O3. Ozone is formed when oxygen molecules are separated by a certain form of solar ultraviolet radiation at high altitudes. The individual oxygen atoms combine with oxygen molecules (O + O2 = O3). In the stratosphere about 300 million tons of ozone are produced daily. There are two kinds of ozone: the high atmospheric ozone and the tropospheric ozone at the earth’s surface.
The ozone layer
The ozone layer is the layer in the atmosphere with the highest concentration of ozone. This layer is situated between approximately 15 and 45 kilometres altitude. The total thickness of the ozone layer is about 15 kilometres. The ozone layer has an important biological function. As mentioned before Ozone absorbs a certain form of ultraviolet radiation from the Sun (UV-B radiation), and it is exactly this type of UV-B rays that cause sunburn, inflammation of cornea and skin cancer. It affects moreover the ecosystem of the oceans. Without the ozone layer the actual life on earth wouldn’t have been possible.
The hole in the ozone layer
In 1974 the American scientists Mario Molina and Sherwood Rowland proved that ChloroFluroCarbons (CFC’s) possibly played an active role in the depletion of the ozone layer. CFC’s are stable industry gasses containing mainly chlorine, fluorine and bromine, used in refrigeration systems, air conditioners, aerosols, solvents and in the production of some types of packaging. The CFC’s cause such an amount of damage to the ozone layer, this layer became alarming thin.
The hole in the ozone layer was discovered in 1985. When British scientists at the Halley Bay station in Antarctica saw the results of their measurements, they were convinced that there was something wrong with their instruments. At once they were replaced, but the results stayed as alarming as before. When their conclusions were published in the scientific magazine Nature, the world recognized that something had to be done and quickly.
A question that is often asked is “Why the hole in the ozone layer occur only over Antarctica?” During the pole night the temperature in the stratosphere drops to sometimes -100ø Celsius. At lower temperatures the demolition process of the ozone molecules is strengthened. At the beginning of spring (September – October) it goes from bad to worse. Each year a cold wedge of ice clouds moves in over Antarctica. This cloud contains CFC’s produced over the industrialised countries. At about the same time of year the The Sun returns to the continent after the winter dark months, and the combination of sunlight, ice clouds and CFC’s form a mixture that destroys the ozone.
Consequences of the depleted ozone layer
The ozone layer protects humans and animals from the harmful UV-B rays of the sun. When this protective layer is reduced, it has dramatic consequences on life. The metabolism of plants is affected, which means a slower photosynthesis. The ultraviolet radiation destroys micro-organisms, which play an important role in the food chain. E.g. When the amount of phytoplankton decreases in the Antarctic ocean, it has also dramatic consequences for mammals such as whales and seals as well as penguins higher up the food chain. Humans are affected most directly by increased chances of skin cancer.
What counter measures have been taken?
On 16 September 1987 the Montreal Protocol was signed. In this Protocol the greatest culprit was dealt with: the CFC’s. In Montreal the participating countries agreed to halve the CFC consumption by the end of the twentieth century. In 1990 the protocol signatories assembled once again, this time to ban CFC’s and halons completely by the year 2000.
The UNEP (the United Nations Environment Programme) started the Programme Action Ozone in 1991. The list of forbidden industrial gasses became longer and the controls became more severe.
All these efforts will only show results in the long term, and in subsequent years the hole has continued to grow. Subsequent studies have shown that the greenhouse effect could aggravate the depletion of the ozone layer. The greenhouse effect makes the stratosphere colder by which the ozone molecules degrade faster. More drastic measurements may have to be taken in the future. Especially in the developing countries and in the former Soviet states, where the ban on CFC production isn’t well policed or observed.