The atmosphere is the layer of gases that goes all around planet Earth. 99 % of these gases are nitrogen and oxygen; another example is carbon dioxide (0.04 %). The atmosphere protects the Earth and keeps it warm. It also protects all life from UV radiation.

The gases in the atmosphere help raise the planet’s average temperature through the greenhouse effect. Human activities that emit carbon dioxide (CO2) or methane contribute to an even warmer planet, leading to global warming and climate change. 

The four layers of the atmosphere

The Earth’s atmosphere has four layers. They are known as the troposphere, stratosphere, mesosphere and 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, separating the atmosphere and space at 100 km from the Earth is still the most common.

The troposphere

The most critical layer of the atmosphere is the troposphere. It is the lowest layer, meaning it is closest to the ground. The troposphere contains the weather and climate on Earth. More so, greenhouse gases like carbon dioxide (CO2), methane and water vapour move here. Therefore, this is also where clouds are. Although, clouds can move further up the atmosphere as well. 

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 being as high as 17 km at the Earth’s centre, the equator. The troposphere equals around 70 to 80 % of the whole atmosphere. 

The history of the atmosphere

The Earth most likely lacked an atmosphere when it came into life 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 make it disappear into space, while nitrogen and oxygen form much of the atmosphere that we know today. Incidentally, the term atmosphere also describes the layer of gases around other planets. Furthermore, the shortened form for the atmosphere is atm, which also refers to a measure of pressure. 

Atmospheric pressure

The atmospheric pressure (atm) is the pressure within the atmosphere around the globe. It is an essential factor in the Earth’s weather and climate because variations in pressure directly affect the planet’s wind and storm patterns. The atm creates high and low pressures. 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 pressure, causing issues with television signals. 

Source: SMHI