Our present atmosphere consists mainly of nitrogen and oxygen but carbon dioxide, water vapor and pollutants play an important part in climate production. Although the amount of carbon dioxide in the atmosphere is small the effects are great. This gas is needed by organisms for photosynthesis,the process by which some organisms make their own food. This gas also plays an important part in the greenhouse effect. Water vapor varies from place to place in the atmosphere. Two main reason for this are the temperature of the air and the nearness of large bodies of water. As water vapor absorbs energy from the sun we can see it as an important climate factor. Pollutants are constantly being added to our atmosphere naturally or by man. These pollutants may effect the amount of solar radiation reaching the earth, increase the greenhouse effect and/or destroy the ozone layer. More information must be gathered about the past before we can truly tell their effects.
As for our present climate conditions, the polar zones average temperatures are below 10 degrees celsius. Little precipitation falls in this zone. Most areas of Alaska are in this zone.
The temperate zone has temperatures ranging from 10 to 18 degrees celsius and receives precipitation in the form of snow and rain. The continental United States are in this zone. The tropical zone has the highest temperatures and also very humid. It stays above 18 degrees celsius. Most areas of Hawaii are in this zone.
