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 fall the least. Such differences in air pressures occur everywhere, depending on the intensity of the sun’s heat. This air pressure difference results in formation of winds. Winds transport moisture laden clouds from one place to other and have a profound impact on the weather.
4. The heat generated by the sun facilitates the water cycle, upon which climate depends. When the sun’s energy heats up the oceans, water evaporates and the vapors rise to the upper levels of the atmosphere. On encountering the cool air at the higher altitudes, these vapors condense as clouds. When the amount of moisture in the clouds become dense, they precipitate in the form of rains, snow, hail, thunderstorms and the like.
Thunderstorms form when this process happens rapidly and with a greater intensity. When the surface heats up greatly, moisture-laden air rises very high into the atmosphere because of its much lower density, while cold air rushes in behind it. The rapidly ascending column of air is cooled and water condenses, but since more air has been heated and pushes up from beneath, the column grows higher and higher.
5. The sun’s heat warming the air also plays its part in the phenomenon of land and sea breeze. Land heats up and cools down more quickly than the sea. During the day the air above the land heats up, becomes less dense and rises. The atmospheric pressure above the land thus drops and air moves in from above the sea, where the air pressure is higher. This causes a sea breeze. During the evening, the temperature of the land drops much faster than the sea. The air above the sea becomes hotter than the air above the land, so it rises and a breeze flows from the coast out to sea, reversing the effect.
6. Solar winds are a steady stream of energetic particles and magnetic fields that continuously flow out from the sun. When these ionized, particles reach the upper part of the earth’s atmosphere they move throughout the magnetic force lines of the North and South poles. They produce glowing colors, commonly known as Aurora Borealis in the North, and Aurora Australis in the South. These particles affect the electrical properties of the planet and alter the atmosphere by changing air pressure and air circulation leading to changes in weather.
Variations in the flow of solar winds alter the amount of ozone in the stratosphere, popularly referred to as the ozone layer. Ozone absorbs the harmful ultraviolet rays of the sun, and decrease in ozone means such harmful radiation would touch the earth’s surface.
The flow of solar winds is not constant. They decline at times, and when they do galactic cosmic rays readily enter the Earth’s atmosphere promoting atmospheric conditions that could be responsible for cloud formation and severe weather.
7. Solar Flares are explosions deep inside the sun that burst out. When the extreme heat produced by these flares reach the earth, temperatures rise, resulting in heat waves and increase in air pressure. Solar flares are a regular occurrence. However, their frequency increases with the change in the solar cycle that happens once every eleven years.
8. At times, a bunch of plasma on the sun suddenly becomes buoyant and lifts off of the sun. This is called Coronal Mass Ejections (CME)’s. They travel faster than the solar wind and drive a shock wave ahead of them. When this CME’s hit the earth, they result in geomagnetic storms and a beautiful display of auroras.