Part one of term paper
The importance of the stratospheric ozone layer, which filters out most of the sun's harmful ultraviolet radiation, in protecting the Earth's surface from the harmful effects of solar ultraviolet radiation has been recognized for many decades. It was not until the early 1970s, however, that scientists began to actually grasp the fact that e ...

Part two of term paper
... has not been determined, yet scientists are aware of its reality and harm to humans. Many scientists believe global warming is caused by the increase of carbon dioxide in the Earth's atmosphere, while other scientists believe that the health threat caused by global warming is due to an unusual interaction between cosmic rays and clouds as well as other natural occurring events. The National Weather Service announced that 1998 was the warmest year (on record on average, around the world). A recen ...