A fundamental premise of all scientific research is that scientists can make measurements, expressed in precise mathematical terms, of conditions and events. Indeed, some argue that a field of study can only be called a science to the extent that the data being collected can be mathematically measured. These criteria apply to environmental science as they do to other physical and biological sciences.

Measurements serve a number of functions in environmental studies. One is to provide baseline information about certain aspects of the environment. A source of concern to scientists and non-scientists alike is the change that appears to be taking place in the earth's ozone layer. Mounting evidence appears to suggest that, as a result of human activities, the concentration of ozone in the stratosphere seems to be decreasing. That finding is significant because the ozone layer acts as a shield against potentially...