Lesson 27:Climate change, global warming


    It is the long term statistical expression of short-term weather. Average long-term weather of an area is called ‘climate’. Climate is determined by temperature and preparation. Changes in climate can be defined by the differences between average
    conditions at two separate times. The global climate system is a consequence of and a link between the atmosphere, oceans, the ice sheets (cryosphere), living organisms (biosphere) and the soils, sediments and rocks (geosphere).

    The earth is surrounded by the atmosphere, which is the body of air or gases that protects the planet and enables life. The air of our planet is 79% nitrogen and just under 21% oxygen; the small amount remaining is composed of carbon dioxide and other gases. There are five distinct layers of the earth.


    • Troposphere: The layer of the atmosphere closest to the earth is the troposphere. This layer is where weather occurs. It begins at the surface of the earth and extends out to about 4-12 miles. The temperature of the troposphere decreases with height. This layer is known as the lower atmr.
    • Stratosphere: It extends to about 30-35 miles above the earth’s surface. Temperature rises within the stratosphere but still remains well below freezing.
    • Mesosphere: Temperature falls with increasing altitude. It lies about 35 to 50 miles above the surface of the earth.
    • Thermosphere: It rises several hundred miles above the earth’s surface, from 50 miles up to about 400 miles. Temperature increases with height. This layer is known as the upper atmosphere.
    • Exosphere: Extending from the top of the thermosphere to 6200 miles above the earth is the exosphere.
    • Weather: Troposphere has a particular set of physical properties, including temperature, pressure, humidity, precipitation, sunshine, cloud cover, wind direction and speed which are called weather.

Last modified: Wednesday, 4 January 2012, 8:41 AM