The Open Door Web Site : Biology : Problems and Concerns caused by Human Influences on the Environment : Depletion of the Ozone Layer and the Greenhouse Effect

The atmosphere is divided into different layers. About 35 km above the surface of the Earth is a layer called the ozone layer. One of the important functions of the ozone layer is that it filters out much of the dangerous ultraviolet (UV) radiation in the Sun's rays. This means that most of the UV radiation never reaches the Earth's surface. Ultraviolet radiation is dangerous because it can cause cancer. This is why it is dangerous to sunbathe too much, since it increases the chances of getting skin cancer.

Some industries make chemicals called chloroflourocarbons (CFCs). These gases are still used in some aerosol spray cans. They are found in refrigerators where they are used as coolant gases. They are also used to produce foam rubber. CFCs are not found naturally; they are completely synthetic.

When CFCs escape into the atmosphere, they rise up and reach the ozone layer. Here the CFCs break down the ozone. This effect was first noticed by British scientists working in Antarctica. The scientists discovered that there is a region of the sky over Antarctica where the ozone layer is much thinner than normal. This is referred to as the `hole in the ozone layer'. More recently, a second `hole' has been found over the Arctic, stretching over Europe.

The industries which use CFCs are looking for alternative gases which, hopefully, will not pollute the atmosphere. In many countries, scientists have convinced governments to make CFCs illegal. That is why most aerosol cans are no longer made using CFCs. Other products, however, still contain these gases and CFCs continue to reach the ozone layer.

Scientists believe that the damage to the ozone layer will have two effects on the Earth's surface:

First, that the extra radiation will cause the lower atmosphere to warm up, and this will add to the greenhouse effect.
Second, that the increase in UV radiation would harm many of the Earth's organisms including humans. Scientists expect that the frequency of reported cancer cases will increase

Ever since humans learned to use fire, half a million years ago, they have not only obtained energy from burning things, but they have also produced smoke and gases such as carbon dioxide (C0₂) which pollute the atmosphere. As the demand for energy has increased, so has the demand for new fuel. By burning larger quantities of wood or coal (and more recently petroleum products, such as gasoline and natural gas), humans have created more and more air pollution. One threat this pollution poses is that it might throw off he delicate balance of global temperature, which is regulated by the greenhouse effect.

Some gases, such as carbon dioxide, are capable of trapping the heat which is produced when sunlight warms up the Earth's surface. The heat trapped by the carbon dioxide will increase the temperature of the atmosphere. The more C0₂ in the air, the hotter the atmosphere will get. Gases which have this effect are known as greenhouse gases since the glass around a greenhouse works in the same way. The greenhouse effect is very important for life on Earth. Without it, much of this planet's surface would be too cold for living things.

Anything which causes a change in the percentages of the gases in the atmosphere can be regarded as atmospheric pollution. Sometimes excess C0₂ can be introduced into the atmosphere because of a natural event, such as a volcano erupting or a forest burning naturally after a lightning strike. Most atmospheric pollution today, however, is related to human activity. Unlike natural pollution, human-related pollution occurs on a daily basis all over the world. Unfortunately, human-related pollution is often longer-lasting and is increasing as the number of people on Earth continues to grow.

It is impossible to predict the future with any certitude but what is known for sure is that humans have nearly doubled the amount of carbon dioxide in the atmosphere over the last few centuries. If such pollution continues, it could disturb the annual cycles of hibernating animals or upset the flowering seasons of some plants. Of course, some plants and animals might be able to adapt to a gradual change in the atmosphere, but many would not be able to.

The Debate Concerning the Greenhouse Effect
Scientists who say that the greenhouse effect is increasing uncontrollably.	Scientists who say that there is nothing to worry about.
The Earth's temperature could rise by 3°C by the year 2050. If the average temperature of the Earth does go up 3°C, it would change the habits of many living things.	The water in the oceans as well as plants and other photosynthetic organisms will be able to absorb the excess carbon dioxide and use it to grow better. No temperature change will occur.
Temperatures have already begun to increase. Average annual temperatures are hotter now than 50 years ago.	Such changes are not due to pollution, only to natural long term cycles in climate.
An increase in global temperatures would cause the polar ice caps to melt partially and cause massive flooding.	As a floating piece of ice melts, the volume it displaces does not change. Even if the ice that is not floating starts to melt, the warmer temperatures would result in more evaporation. If there were any flooding, it would be negligible for these two reasons.
Who is right and who is wrong? Only time will tell. The scientists concerned with the greenhouse effect say that atmospheric pollution must be controlled now because later, it might be too late; the atmosphere might soon be damaged beyond repair.