by Nayab Naseer

Created on: March 14, 2009

The Sun is a burning ball of mostly gaseous hydrogen with a surface temperature of 6000 degrees centigrade, large enough to hold a million Earths. The importance of the sun rests on the fact that it warms the surface of an otherwise cold and lifeless earth and makes possible the existence of life on this planet.

The wonder of the sun is that its heat reaches Earth at just the right level to meet human being's needs. If the earth were a little distance closer to the sun, the water in the oceans would boil off, and if the earth were a little further away from the sun, all water would remain frozen. Another of the sun's wonder is its energy reaching Earth despite the 93 million miles of emptiness between them, bearing in mind that normally a vacuum cannot transmit heat!

That the Sun plays a critical part in the Earth's climate system is indisputable. It does so in the following ways:

1. The suns rays touch the earth's surface and warm it up from an otherwise uninhabitable -250 degrees centigrade to -18 degree centigrade. These rays touch the earth's surface and reflect back to outer space. However, on the way back, the greenhouse gasses present in the atmosphere trap a further portion of this heat, in the form of infrared radiation. This further raises the average surface temperature to a more comfortable 15 degree centigrade. In this way, the Sun's radiation and the Earth's blanket of greenhouse gases sustain the mean global temperature at a level supportive of life.

2. The temperature in the earth is not constant. It varies with both time and place, and this again depends on the heat from the sun. How the Earth's surface temperature adjusts to a given change in solar radiation depends on the processes by which the climate system responds to variations in the energy it receives.

The difference in temperatures depend on the tilt of the earth away from the sun that impacts the quantum of sun's rays that fall on the specific surface, the rotation of the earth and other factors. This phenomenon influences the circulation of ocean currents, winds and convention, integral to the earth's weather process, and is the basis for different seasons like summer, winter, spring, and autumn.

3. The energy from the sun heats up the air and influences the pressure of the air. Warm air is less dense than cool air, and rises above it. This means that the air pressure above the equator, where the sun's rays fall the most is lower than the air pressure above the poles, where the sun's rays

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