The Sun is the energy source of all life on Earth. Most of the solar energy arrives on Earth in the form of light and heat. The climate depends on the way in which this energy is distributed between the atmosphere and the earth's surface. The weather is warmer where more energy reaches the surface, and colder where less.
The Earth's atmosphere is dense, and a good part of solar energy is lost when it passes through it. The atmosphere prevents the most harmful rays from reaching the surface (X-rays, gamma rays and much of the ultraviolet rays).
Gases and dust particles in the atmosphere cause a small part of the energy to disperse before reaching the ground. It is this dispersion of light that produces the blue color of the sky. Another part is absorbed by water vapor or reflected by clouds and oceans. The amount of solar energy that reaches the surface can be 4 times greater on a clear day than on a very cloudy day.
The amount of energy absorbed by the surface depends on latitude, since the angle at which the light reaches varies. On the equator the light enters in a straight line, so it absorbs more heat and the weather is warm. The further we move away from the equator, the light arrives at a more closed angle, it goes through more atmosphere, more energy is lost and the weather is colder. In areas near the poles, only 5% of the heat reaches the surface.
These variations cause changes in pressure in the atmosphere and form wind currents. Wind currents join oceanic and produce phenomena such as El Niño, monsoons, hurricanes, etc.
The angle at which the light arrives varies at each time of the year. It is because the Earth rotates on an inclined axis while orbiting the Sun. Therefore, the amount of solar energy received at each time of the year is different and the seasons are created.
Solar cycles also affect the Earth's climate. There is a relationship between the amount of sunspots and periods of long droughts or floods. The amount of radiation that reaches the surface also varies. Between the 16th and 18th centuries there was a cooling known as the Little Ice Age, coinciding with a period in which there were hardly any sunspots. Currently solar activity is very high, and it is studied whether it could be related to climate change.
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