The Atmosphere

The atmosphere is a layer of gases, commonly known as air, that surrounds the Earth and is retained by the Earth’s gravity.
It protects all life on Earth by absorbing ultraviolet solar radiation and reducing the temperature differences between day and night.
The atmosphere is divided into five main layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Composition of the Atmosphere

The Earth’s atmosphere is made up of a mixture of gases, the most abundant of which is nitrogen (around 78%).
Oxygen makes up around 21% of the atmosphere. The remaining 1% is comprised of other gases, including argon, carbon dioxide, and traces of other gases.
Water vapour also forms an important part of our atmosphere, though its concentration varies.

The composition of the Earth’s atmosphere has changed significantly over the Earth’s 4.6 billion year history.
The early atmosphere was likely composed mainly of methane, ammonia, and water vapour.
There was a minimal amount of oxygen, and it was only around 2.3-2.4 billion years ago that the level of oxygen began to increase in a process known as the Great Oxidation Event.
This oxygen resulted from photosynthesis by early microscopic plants.

Pollution can often lead to significant changes in the composition and overall health of the atmosphere.
Major pollutants include carbon dioxide, sulphur dioxide, methane, ozone, and Nitrogen oxides (NOx).
These pollutants can lead to various environmental issues such as climate change, acid rain, and smog.
Solutions to reduce atmospheric pollution include green energy sources, more efficient utilization of fossil fuels, and pollution control technology.

Greenhouse gases in the atmosphere, such as carbon dioxide, methane, and water vapour, trap heat from the sun, preventing it from escaping back into space. This is known as the greenhouse effect.
This natural process helps to maintain the Earth’s temperature, making it warm enough to support life.
However, an increase in greenhouse gases, mainly due to human activities like burning fossil fuels and deforestation, enhances the greenhouse effect leading to global warming.

The Ozone layer is a layer of ozone high up in the Earth’s atmosphere in the stratosphere.
It plays a crucial role in protecting life on earth as it absorbs most of the Sun’s harmful ultraviolet rays.
However, certain chemicals, particularly CFCs (chlorofluorocarbons), can damage the ozone layer causing ‘holes’ – reduced concentrations of ozone, and leading to what is termed as the ozone hole.