Climate is defined as the average weather conditions of an area over very long periods of time. This means hundreds of years.
There are three major climate regions on the earth. Each based on the average weather conditions of the area.
These regions are:
Polar—60 to 90 degrees north or south of the equator.
These are the coldest of the zones as they do not receive radiation in the same amounts and intensity as the other zones. They also contain the ice caps that reflect sunlight.
Temperate—30 to 60 degrees north or south of the equator.
The temperate zone is affected by both tropical and polar air masses. This means that if a location is nearer the polar zone, during the winter season snow will fall. If nearer the tropical region, they will receive rain during the same season.
This region also has a wider range of weather conditions during the year because of the location of the other two zones.
Tropical—0 degrees to 30 degrees north or south of the equator.
This zone has the highest temperature as it receives the most solar radiation throughout the year.
Thanks to nature, we have learned that the climate of the earth has changed over time. Radioactive dating, tree rings, fossils, ice cores, ocean floor samples and corals have supplied information for climatic change time frames .
We believe that these changes were due to a variety of reasons:
1. Cyclic of the earth’s orbit from round to elliptical every 100,000 years.
2. Change in tilt of the earth’s axis.
3. Precession—Wobbling that operates on a 20,000 year cycle.
4. Continental Drift.
5. Evolution of life forms.
The early climate of the earth is hard to follow because of the lack of a rock record. Due to the movement of the earth’s lithosphere the rocks have been recycled destroying any evidence that might have existed.
It is believed that the early atmosphere a contained a plentiful amount of carbon dioxide for the greenhouse effect. The earth’ s interior was warmer and contributed to a great deal of volcanic activity. These volcanic eruptions put water vapor and other particles into the atmosphere that formed clouds and blocked out solar radiation. The earth then began to cool allowing rain to fall. As time went on, oceans began to form and store heat. The water cycle then began.
There was no free oxygen in the atmosphere at this time. Ozone could not be formed to filter out the radiation that is harmful to life. Eventually primitive life began and started to add oxygen to the atmosphere.
Our present atmosphere contains mainly of nitrogen and oxygen. However, there are small amounts of other gases that play a major part in climate production.
Carbon dioxide is needed by organisms for photosynthesis and the greenhouse effect. Water vapor plays an important part by absorbing energy from the sun and pollutants may effect the amount of solar radiation that reaches the earth.
As for future climates, we will continue to have change due to continental drift and other natural factors that will continue to interact.