Background Information: Danger of Increased Greenhouse Gases

As far back as Greek and Roman times, people built structures which created an indoor environment suited to growing plants throughout the year. This enabled the gardener to establish a measure of control over growing conditions and more particularly extend the growth period into the colder seasons of the year. In this manner, the gardener was better able to provide fresh fruits and vegetables when needed. Today these structures are usually made of glass or plastic, but still allow us to maintain year-round greenery and so are called greenhouses as described earlier. There are similarities between the greenhouse and the earth's atmosphere in the manner in which they operate.

How Does the Atmosphere Trap Heat?

Though the atmosphere might appear to be an enormous zone of empty space, molecules of many gases are moving within it. The air we breathe, for instance, is rich in nitrogen and oxygen. These molecules allow visible light to pass through. The atmosphere is very much like warm clothing. A coat or a blanket holds body heat close to our bodies. Similarly, atmospheric gases made up of triatomic or polyatomic molecules hold the earth's heat close to the earth. The gases that operate in this way are named greenhouse gases. In general terms, increased greenhouse gas concentrations result in increased atmospheric temperatures.

In fact, natural greenhouse gases are essential to life on earth. These gases maintain the average surface temperature of our planet at a comfortable 15.5 degrees Celsius. If there were no greenhouse gases in the atmosphere, all of the heat radiated from the Earth's surface would disappear into outer space. The planet's average temperature would be well below freezing and far too cold for most life forms.

Naturally, the earth's atmosphere has always contained greenhouse gases. However, increasing the concentrations of greenhouse gases in the atmosphere may increase the earth's temperature. Currently, human activity is causing this to happen. The effects of higher average temperatures on earth to be experienced by people and their environment could cause devastation and furthermore, such a climate change promises to be irreversible.

Many gas molecules, especially those made up of at least three atoms (e.g., carbon dioxide, methane, nitrous oxide, water vapor, and ozone), allow most visible light and some infrared light to pass through them and to reach the ground. However, almost all outgoing infrared waves, re-radiated and rising from the Earth's surface, are blocked. As infrared energy ascends into the atmosphere, it is absorbed by these same gas molecules and gradually released into the Earth's atmosphere. This results in heating and increased temperatures leading to global warming of the atmosphere.

How Do Greenhouse Gases Affect Climate?

The amount of carbon dioxide from combustion of fossil fuels, as explained in the previous section, released an enormous volume into the atmosphere. Between the years 1870 and 1980, the average concentration of atmospheric carbon dioxide increased from 290 to 335 ppm (parts per million) and it is now standing at about 350 ppm. This leads to an increase in temperature globally, hence known as global warming of the atmosphere.

It is common to lay the blame for excessive emissions of gases unfriendly to the environment at the feet of the large industrial nations of the world, like Europe and North America, but it is important to keep in mind that we must all maintain vigilance. For example, an Asian study recently reported that the amount of carbon dioxide released into the atmosphere from the Indonesian forest fires during late 1997 associated with the El Niño-induced droughts at that time (but also questionable farming practices) was equivalent to the amount generated throughout the whole of Europe in one year.