Variability (Natural, Patterns of, Climatological)

Weather is constantly changing. Climate, in contrast, is a record of the variations in weather over long periods of time. For example, the climate of the Ice Age, which, in terms of geologic ages was a mere few thousand years ago, was extremely cold; since then the global climate has warmed considerably. However, the long-term trends in the climate, whether of localities, continents, or even of the globe, vary in discernable patterns. One factor that has affected the variability of the climate has been continental drift. Over millions of years, continents moved from warmer regions to colder regions and vice versa. However, of interest to climatologists are variable patterns that are more intermediate.

From the 1940s until the early 1970s, the climate in North America was cooling; since then the climate has been warming. Today, many scientists fear that global warming is occurring because of human activities such as the burning of fossil fuels, especially coal, natural gas, and petroleum. The problem with this assessment is that over the last 10,000 years there have been periods of warming and cooling in North America. In addition, studies of the growth rings of trees have shown variations in the patterns of growth that indicated periods that were wetter and periods that were dryer. The general conclusion climatologists and other scientists have made is that there are variations in the patterns of rainfall, temperature, winds, and other meteorological phenomena. These variations have a number of causes.

The oceans covering over 70 percent of Earth's surface are a major influence on the earth's climate; they affect the weather constantly. As the sun strikes the surface of the oceans and sea—especially in the equatorial regions—it warms them, causing evaporation. The resulting cloud covers are driven by the winds onto land masses where they interact with the colder air masses of the polar regions, causing rain and snow. The oceans also act as heat traps by absorbing vast amounts of heat, which is then slowly released and, in the case of the warm currents such as the Gulf Stream, transported to colder regions.

Many climatologists, meteorologists, and other scientists believe that changes in the oceans can create long-term patterns in the weather. Changes in evaporation rates can affect the salinity of the oceans. Even small changes can produce significant variations in the patterns of the climate.

Oceans affect the weather constantly; clouds driven onto colder land masses can cause rain and snow.

It is essentially the way in which heat is distributed and redistributed in changing patterns that causes variability in the climate. Studies of the way in which the oceans absorb and then spread the heat from the sun via ocean currents, hurricanes, typhoons, and by moisture patterns are pointing to a better way of understanding climatic variations.

Because there are naturally occurring global patterns of warming and cooling, many scientists are of the opinion that the term global warming is misleading. The better term to use to reflect variation in global climate is global climate change. This term has been suggested as a means for including the naturally occurring changes that are due to more than [Page 1888]just the release of vast amounts of carbon dioxide into the atmosphere since the beginning of the Industrial Revolution in the late 1700s.

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