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Climate is the long-term
state of the atmosphere at a particular site--in a sense,
the "average weather" over a long period of time. Climate varies tremendously
around the globe, and not randomly.
At the end of the last ice age, about 12,000 years ago, glaciers covered much of Europe and North America.
Fed by ocean waters, the polar ice caps thickened and expanded, causing global sea level to drop far
below its current level. Still recovering from the Ice Age, the Earth is about 5°C (9° F) warmer
today than it was then, and global sea level continues to rise. The past century alone has seen
global temperature increase by 0.6° C (1° F), and the average global sea level over the past
decade has risen steadily. Is this the result of Global
Warming or Global Climate Change?
Here is what we know about the Earth's climate:
- At the poles, it's bitterly cold--below freezing all the time, and very dry.
- At the equator (at sea level), it's always hot and usually rainy, but it never freezes.
- At mid latitudes, climates are in between these two extremes
--temperate--but
- Climates on the east coasts of continents are wet, with cold winters and hot summers,
- Climates on the interior parts of continents are dry, with even colder winters and hotter summers,
- And climates on continental west coasts are mild, with rainy winters and dry summers.
How do we account for these phenomena? Several factors are of paramount importance:
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