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atmosphere: Role of the Earth's Atmosphere

The earth's atmosphere is the environment for most of its biological activity and exerts a considerable influence on the ocean and lake environment (see biosphere). Weather consists of the day-to-day fluctuations of environmental variables and includes the motion of wind and formation of weather systems such as hurricanes. Climate is the normal or long-term average state of the atmospheric environment (as determined in spans of about 50 years). The atmosphere protects earth's life forms from harmful radiation and cosmic debris. The ozone layer also protects the earth from the sun's harmful ultraviolet rays; seasonal holes in the ozone layer, the first detected above Antarctica and the Arctic in the 1980s, caused considerable alarm about the consequences of air pollution. Subsequently there has been increasing recognition of the role of air pollution and other aspects of human activity in global warming and climate change. Meteors strike the thermosphere and mesosphere and burn from the heat generated by air friction.

See also Van Allen radiation belts.

The Columbia Electronic Encyclopedia, 6th ed. Copyright 2012, Columbia University Press. All rights reserved.

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