Environmental FACTORS are, naturally, variable. For instance, air temperature varies on a diurnal and annual basis. In order to measure sustained temperature changes, we take average values for days, MONTHS, seasons, years, and even longer periods.

Then, the similar averages are compared when it is found that the mean temperature for one year is greater than that in the previous year; we know that a change has occurred.

It MUST be kept in mind that average values should not be treated as some sort of norm. Average values for all the principle atmospheric variables over a period of thirty years are used to defined “climatic norms”. This term is often misleading, since it tries to establish that the climatic norms are somehow permanent.

However, current thinking suggests that the climate is ever changing. The climatic norms of one generation may be another generation’s climatic extremes. Thus, we may conclude from this argument that — change is the norm, constancy the exception.

In this context, scientists have found that environmental variables DISPLAY three basic types of changes:

• A discontinuity, which is an abrupt and permanent change in the average value,
• A trend, which is a smooth increase or decrease (not necessarily linear in nature) in the average, and
• A function, which is a regular or irregular change characterized by at least two maxima (or minima) and one minimum (or MAXIMUM).

Environmental factors are, naturally, variable. For instance, air temperature varies on a diurnal and annual basis. In order to measure sustained temperature changes, we take average values for days, months, seasons, years, and even longer periods.

Then, the similar averages are compared when it is found that the mean temperature for one year is greater than that in the previous year; we know that a change has occurred.

It must be kept in mind that average values should not be treated as some sort of norm. Average values for all the principle atmospheric variables over a period of thirty years are used to defined “climatic norms”. This term is often misleading, since it tries to establish that the climatic norms are somehow permanent.

However, current thinking suggests that the climate is ever changing. The climatic norms of one generation may be another generation’s climatic extremes. Thus, we may conclude from this argument that — change is the norm, constancy the exception.

In this context, scientists have found that environmental variables display three basic types of changes: