Greenhouse Effect and Ozone Depletion
An Explanation of The Greenhouse Effect and the Destruction of the Ozone Layer.
The Earth’s atmosphere can be divided into several sections. Up to around 12km from the Earth’s surface is known as the troposphere. This is where the greenhouse effect takes place. From about 12-50km we have what’s called the stratosphere. This is where the ozone problem occurs. These two issues (greenhouse and ozone) can be treated as separate problems but, as we will find out later on, they can be related in some ways.
THE DESTRUCTION OF THE OZONE LAYER
Ozone is a pale blue gas that is made of three oxygen molecules. The oxygen we breathe is made up of two oxygen molecules (what I will mean by oxygen wherever it occurs later on). Ozone is produced by electrical discharges in the atmosphere such as lightning and is found in the stratosphere in large quantities. It has a unique property in that it can absorb ultra-violet (UV) radiation transmitted from the sun. UV radiation is what causes skin cancer and many other health problems. We receive very little of it due to the actions of ozone.
Ozone stops UV radiation from reaching us via a repeating process:
- Ozone absorbs the UV radiation in a reaction to form oxygen.
- Oxygen then converts back to ozone in another chemical reaction.
- The ozone then absorbs more UV to return to oxygen, and so on.
In effect, we have a continuous process that ensures a permanent blanket of ozone in the stratosphere. The blanket is pretty much self-sustaining.
HOW IS THE OZONE LAYER BEING DESTROYED?
There are two major gases that just love to eat ozone in another repeating process. They are Chlorofluorocarbon (CFCs) and nitric oxide. CFCs are used as a propellant in some spray cans, in the cooling systems of refrigerators, and in the production of foam containers (such as those that contain your Big Macs from McDonald’s).
Nitric oxide comes from fertilizers. When CFCs float up to the stratosphere they break down and release chlorine. The chlorine then reacts with the ozone to form oxygen, nitric oxide acts in a similar fashion to the chlorine. So, what we end up with is CFCs and nitric oxide eating up the ozone that was previously reserved for incoming UV radiation. The ozone layer is depleted in strength and more UV radiation penetrates to the Earth’s surface and us.
HOW BAD IS THE OZONE PROBLEM?
Measurements show that there had been a dramatic reduction in ozone at both the north and south poles. The damage now extends to the southern tip of Australia and New Zealand during the summer months. Recent measurements of ozone concentrations in the stratosphere over southern New Zealand have indicated a reduction of 20% in the ozone layer compared with measurements made before 1979.
CFCs are now recognized as being the main contributor to the ozone problem. At the infamous Montreal meeting in 1987, 27 countries pledged to reduce CFC production by 50% by the end of the 20th Century. However, it has been shown that this will only dent the ozone depletion rate. It has also been shown that to stop the depletion and leave the damage at 2% (an average value over the whole world) we would have to stop all CFC production by 1997.
THE GREENHOUSE EFFECT
The greenhouse effect is what keeps the Earth warm. The lower atmosphere (troposphere) acts like a glasshouse by trapping heat and so regulates the Earth’s temperature. This stops the Earth from getting excessively cold during the night or excessively hot during the day. This is one of the factors which contribute towards sustaining life on Earth as opposed to a planet such as Mars.
Oases in the troposphere (called greenhouse gases) achieve this by being relatively transparent to incoming light waves but are relatively opaque to the reflected waves of radiation. Why? Well, incoming light waves have a long wavelength but when they hit the Earth they are then reflected with much shorter wavelengths.
Certain gases in the troposphere will let through the longer wavelengths of radiation but will absorb the shorter wavelengths on their way out and reflect them back to Earth. Thus heat is retained and the Earth is kept warm. These gases include carbon dioxide (CO2), methane, nitrous oxide, CFCs, ozone, and water vapor. Remember that we are only talking about the greenhouse effect at the moment. Some of these gases also take part in the ozone problem which occurs in another part of the atmosphere as explained previously.
SO, WHAT’S THE PROBLEM, YOU SAY?
The dilemma of the greenhouse problem is that our modern industrial environment is adding more greenhouse gases to the atmosphere. Our glasshouse that sustains life is becoming more efficient and, as a result, in the future, we can expect that the Earth will get warmer. Scientists have predicted that global temperatures will rise by 1 degree in the next 10 years and 3 degrees by the year 2050.
SO WHAT YOU SAY? MORE BEACH DAYS
Unfortunately, it’s not as simple as this. When we talk about global temperatures we are referring to what should be the average over hundreds of years and over the whole world. The last time the global temperature was 3 degrees higher than today was about 2 or 3 million years ago.
Pretty heavy stuff when you consider that all these extra greenhouse gases have been added in the last 200 years. Predictions about what could happen because of the addition of extra gases to the greenhouse are still only calculated guesses. What we do know is that the sea level will rise due to the melting of polar icecaps (along with the thermal expansion of water) and weather patterns have the potential to change dramatically.
The atmosphere is so complex that I believe nobody really can be 100% sure about how the weather will change. Despite all this, we do know that the following additional changes are likely for the United States:
- increased rainfall in summer (50%) and a decrease in winter (20%);
- large regional changes in soil moisture, water runoff, and supplies, heavily damaging present farming areas;
- tropical cyclones further south and more frequent;
- more frequent floods and droughts;
- the greater salt content of inland waters;
- higher snow-lines.
All this talk about the greenhouse and ozone problems sounds like predictions of doomsday, but I believe we can cope with the situation if we act to reduce our society’s addition of damaging gases to the atmosphere. We have a technologically advanced society which, I believe, can adapt to cope with the greenhouse effect and the destruction of the ozone layer. We can reduce the effects. Look at the causes and then decide for yourselves what we can do. I believe the following steps are in order:
- reduction in the use of fossil fuels (petrol, coal, etc.) which produce the CO2 (50% of the greenhouse problem);
- reduction in the use of CFCs by using alternatives that are available CFCs along with water vapor and ozone form 27% of the greenhouse problem. CFCs are also the major contributor to ozone destruction;
- using whatever means are available to reduce methane (18% of the greenhouse problem). Methane is generally a product of decomposition (rotting) of organic matter;
- using whatever means are available to reduce nitrous oxide. Nitrous oxide contributes 5% to the greenhouse problem. It then attacks the ozone layer in the form of nitric oxide.
We can beat the dilemmas of the greenhouse effect and ozone layer if we rationally address them now. Think about it, talk to people, ask questions and, most of all, kick a few politicians’ butts in order to keep this planet healthy for yourself and your families. When you vote, ask yourself where the’ political candidates standoff environmental issues.
If we can raise the public awareness over the problems we are inducing on our planet, I believe that we can give the future a lot brighter prospect than it has today. Careful planning and organization are needed for the environment and this needs to be undertaken by all people. Be optimistic. Don’t piss it off as an impossible dream. Help us make the world a better place to live in.