GLOBAL WARMING is the most controversial effect of air pollution. It is accepted, by most scientists, as the cause for the increase in temperature and the warming period the earth has been going through. The theory of global warming is simple and is best explained by the greenhouse effect. The sun’s rays strike the earth and the ones that pass through the outer atmosphere, easily pass through the lower atmosphere and begin to warm the earth. Heat is reflected back towards space but is trapped by the lower atmosphere which keeps the heat in, just as the glass or plastic of a greenhouse. This process has been going on ever since the earth has had an atmosphere but global warming says that the amount of sunlight the lower atmosphere reflects back to earth is increasing. (Now look at the picture and describe the process yourself.)
The gases that cause the heat to be retained and reflected back to earth are called greenhouse gases, but carbon dioxide is the biggest contributor. Carbon dioxide levels are now 2 times as large as they ever were and the temperature is increasing. This is a definite cause for concern.
WHAT CAUSES THE BUILD-UP OF GREENHOUSE GASES IN THE ATMOSPHERE? 1) ________________________________________
2) _________________________________________, etc.
CURRENT EFFECTS: In the last 20 years the 14 hottest have been recorded. The effects of this increased temperature have innumerable weather impacts. A recent heat wave in Europe left 30 thousand people dead. There have been the most tornadoes in the Midwest during 2005 than ever before. Hurricanes and Japanese typhoons have increased in severity. The warmer water increases precipitation and intensifies the winds. Major floods and droughts will become more common. In short, the weather more and more unpredictable as global warming continues to gain momentum.
Other alarming effects of global warming include melting glaciers. Mt. Kilimanjaro in Africa has lost almost all snow on its peak and it is estimated that it will all have melted in 20 years. Another example of melting glaciers is the tip of Argentina. Years ago it used to be completely frozen but now it is little more than a lake. The most alarming glacier decrease is in the Himalayas. Nearly 40 percent of the entire world’s population get their drinking water from this mountain ranges melting ice pack. In 50 years all but the highest peaks will be devoid of any kind of glacier.
WARMING OF THE FUTURE:
We have all heard the doomsday stories of global warming and they all may be true. The temperature increases are shifting climate zones of warmer regions farther and farther north. Permafrost is the hard frozen earth that makes up most of the land area in northern Canada and Alaska. This layer freezes and refreezes every year but recently it has remained in its swamp like state longer and longer each year. This affects the availability of northern highways. In 1970, the highways that were supported by the permafrost were open 225 days of the year; these same roads are now only open about 75 days. The melting of the permafrost and the resulting slushy ground is toppling trees and houses that were held up by it. The Alaskan pipes built on permafrost are breaking down more consistently.
These temperature changes will not just be affecting permafrost and toppling trees, there are many more dramatic effects global warming has on the world. The advance of warm temperatures towards the poles is causing massive chunks of the ice caps to break off into the ocean. This endangers habit and range for a variety of creatures who seek out colder waters interspersed with icebergs or stable breeding grounds for seals.
Another great problem is rising of ocean levels. The real danger comes from ice sheets covering land masses namely Greenland. If all the ice on Greenland melts, the coast line of the world will plunge as sea levels rise by 20 feet. This will cover most of Florida along with the low-lying lands that most of the Earth’s densely populated areas lie. Millions of people would have to be relocated should land-based ice sheets thaw out.
WHAT IS THE DEPLETION OF THE OZONE LAYER?
There is a deep layer in the stratosphere, encircling the Earth, that has large amounts of ozone in it. The layer shields the entire Earth from much of the harmful ultraviolet (UV) radiation that comes from the sun.
The ozone layer became more widely appreciated by the public when it was realized that certain chemicals mankind manufactures, called chloroflurocarbons (CFCs), find their way up into the stratosphere where, through a complex series of chemical reactions, they destroy some of the ozone and create ozone holes. UV rays easily pass through such holes and may cause skin cancer.
As a result of this discovery, an international treaty was signed in 1973 called the Montreal[ˌmɔntrɪ'ɔːl]Protocol, and the manufacture of these chemicals was greatly, though not entirely, reduced. (Comment on the picture.)