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The Earth’s atmosphere is the layer of gases that goes all around planet Earth. 99 % of these gases are nitrogin and oxygen, another example is carbon dioxide (0.04 %). The atmosphere protects the earth by for example keeping it warm. In fact, the gases help to raise the average temperature on Earth through the greenhouse effect.

More so, human activities that emit carbon dioxide (CO2) and/or methane contribute to an even warmer planet. Hence the global warming and climate change of today. The atmosphere also protects all life from UV radiation.

The four layers of the atmosphere

The Earth’s atmosphere is divided into four layers. These are the troposphere, the stratosphere, the mesosphere and the thermosphere. The layers reach about 100 km up from the Earth’s surface. At least that is where the Fédération Aéronautique Internationale (FAI) puts the limit of the atmosphere. Although, gases can reach as far up as 1000 km before they transition into space. However, it is still most common to separate the atmosphere and space at 100 km from the Earth.

The troposphere

The most important layer of the atmosphere is the troposphere. This layer is the lowest one closest to the ground. You can find the Earth’s weather and climate in the troposphere. It contains gases such as carbon dioxide (CO2), methane and water vapour. Furthermore, water vapour is sometimes excluded as a gas in the atmosphere, hence the understanding of it as 99 % nitrogen and oxygen.

The troposphere reaches about 11 km above the Earth’s surface. It differs slightly depending on the area. For example, it is 7 km at the North and South Poles. While it is as high as 17 km at the Earth’s centre, the equator. The troposphere is equivalent to around 70 to 80 % of the whole atmosphere. This is where the concentration of water vapour creates clouds. Although, clouds can also be found further up in the layers above.

Picture of the atmosphere, taken from space.

The history of the atmosphere

The Earth most likely lacked an atmosphere when it was created about 4.6 million years ago. Over time, gases from the Earth’s interior moved up towards the surface. For example water vapour, carbon dioxide and methane. These were broken down by the unlimited solar radiation, eventually creating hydrogen, nitrogen and oxygen. Hydrogen has properties that made it disappear into space, while nitrogen and oxygen formed much of the atmosphere that we know today. Incidentally, the term atmosphere is also used for the layer of gases around other planets. Furthermore, atmosphere is abbreviated to atm, which refers to a measure of pressure.

Atmospheric preassure

The atmospheric preassure (atm) is the preassure within the atmosphere around the globe. It is an important factor in the Earth’s wather and climate. This is because variations in preassure directly affects the planet’s wind and storm patterns.  Creating high and low preassures. More so, and perhaps more relevant in the past, it can cause “atmospheric disturbances”. For example, this is when radio waves are disturbed by high preassure, causing issues with television signals.

Source: SMHI


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