The Atmosphere


The Atmosphere

Todays Atmosphere:

  • -78% nitrogen
  • -21% oxygen
  • -small proportions of other gases ( carbon dioxide, water vapour and argon)

The Earth is around 4.6 million years old and that means that scientists cannot be certain about the early atmosphere.

  • During the first billion years, there was intense volcanic activity. The volcanoes released gases that formed the atmosphere. These included: water vapour, carbon dioxide, nitrogen, methane and ammonia.
  • As the earth cooled, the water vapour condensed to form the oceans.
  • In this early stage, the atmosphere consisted mainly of carbon dioxide with little or no oxygen.
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The Atmosphere

How Carbon Dioxide Was Reduced:

  • Some of the carbon dioxide dissolved in the oceans to form a weak acid.
  • Sedimentary rock also removed carbon dioxide in the atmosphere.
  • Formation of fossil fuels.
  • Plants took in carbon dioxide in photosynthesis.

How Oxygen Increased:

  • When the oceans were formed, photosynthetic algae evolved. Photosynthesis producd oxygen which entered the atmosphere.
  • Over billions the plants evolved and increased the amount of oxygen.
  • At some point, the level of oxygen reached the point where animals could evolve.
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The Atmosphere

  • Coal is formed from the remains of ferns and trees.
  • If these die in marshy wetlands the they DO NOT DECOMPOSE. That could be due to a lack of oxygen or acidic conditions. These both prevent bacteria from carrying out decomposition.
  • Over time, the plant remains are covered with sediment and compressed. High temperature and pressure creates coal.
  • Crude oil is formed from plankton, and when they die the settle in mud on the sea-bed. If oxygen is not present then they DO NOT DECOMPOSE.
  • Over time, they are compressed by sediment. Heat and pressure then convert them into crude oil.
  • Natural gas is mainly the hydrocarbon methane. Formed in a similar way to oil, and therefore found near it.


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The Atmosphere

Water vapour, carbon dioxide and methane are all greenhouse gases.

  • Energy from the sun travels to the Earth as short wavelength radiation e.g. ultraviolet and visible light.
  • Some of the short wavelength radiation simply reflects back into space but most of it passes easily though the atmosphere. That is because short wavelength radiation does not ineract strongly with the gas molecules in the atmosphere.
  • The energy of the radiation is absorbed when it reaches the surface of the earth.
  • The surface of the earth now radiates the energy as long wavelength radiation such as infrared.
  • Some of the long wavelength radiation interactswith the greenhouse gas molecules in the atmosphere. The energy in the long wavelength radiation is absorbed.
  • Because the energy is trapped in the atmosphere, this causes the temperature of the atmosphere to increase.

The greenhouse effect keeps the temperature of the Earth warm enough to support life. Without the greenhouse effect, the Earth would be too cold for most living organisms to survive. 

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The Atmosphere

  • The amount of carbon dioxide is increasing due to human activity- burning fossil fuels.
  • Carbon dioxide is usually absorbed by plants, however rainforests are now being destroyed by deforestation.
  • Methane is released in agriculture e.g. growing rice in flooded paddy fields. Methane is also released when cows pass wind.
  • The levels of carbon dioxide and methane is increasing, this means that the temperature of the atmosphere is rising as more of the energy from the sun is trapped.

Rising temperatures will increase melting of the polar ice sheets and glaciers, which will lead to increased sea levels. Increased sea levels could lead to more flooding of low-lying areas.

Climate change could lead to more severe weather e.g. more storms in the UK.

It could also change the distribution of animals such as insects, it may even change the distribution of insect-borne dieseases such as malaria.

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The Atmosphere

Many scientists believe that climate change is caused by human activity causing the release of greenhouse gases, this is because the evidence is shared between many different scientists.

These scientists can then criticise the evidence and decide whether it is valid. Scientists call this process peer-review and it allows scientists to detect false claims e.g. based on poor evidence or bias.

However, some scientists believe that the Earth may be going through a hot period, like it has done before and there is evidence to prove. 

There are also many speculations in the media of biased stories. We cannot predict the certainty how much the temperature of the atmosphere will increase.

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The Atmosphere

The carbon footprint tries to give us an idea of how much something contributes to climate change.

The carbon footprint isthe total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.

A lot of energy is spent heating our homes usually from fossil fuels. By insulating our homes or turning down the heating, we can reduce carbon dioxide emissions.

A great deal of carbon dioxide is released by driving cars. We can do this by using public transport such as buses and trains.

A lot of carbon dioxide is produced by generating electricity by burning fossil fuels. We can reduce that by switching to renewable sources of electricity e.g. wind power. 

We could switch to energy saving lightbulbs and turn off appliances at the plug.

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The Atmosphere

Problems with the solutions:

Most of these are expensive and people are reluctant to pay.

In some cases they are inconvenient, for example, many people prefer the convenience of driving over public transport.

To reduce methane emissions, we could eat less beef and less dairy products, the problem with this is that people enjoy eating these and are unlikely to change their diets.

To reduce methane from landfils we can trap the methane and burn it to produce electricity. Methane is a much more powerful greenhouse gas than carbon dioxide, so it is a good idea. However, this process costs money.

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The Atmosphere

Fuels release energy when they are combusted.

The elements in the equation have been oxidised. This reaction is called complete combustion. For complete combustion to happen, we need plenty of oxygen.

If the amount of oxygen is reduced, then we make cabron monoxide instead of cabron dioxide. Carbon monoxide is a toxic gas and it has no colour and no smell.

Producst of combustion include:

  • cabron dioxide
  • carbon monoxide
  • water vapour
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The Atmosphere

Coal contains the element sulfur. So when it is burned the sulfur atoms are oxidised. This produces sulfur dioxide.

Oxides of nitrogen are produced inside engines for example cars. Here, high temperatures cause nitrogen and oxygen from the air to react. This produces a range of different molecules so scientists call them all oxides of nitrogen. (NOx)

Both sulfur dioxide and oxides of nitrogen cause breathing problems in humans (asthma).  They also dissolve in rainwater to form acid rain. Acid rain can damage trees and corrode buildings made from limestone.

Black particles are the particles of carbon (soot) and unburned hydrocarbons. Scientists call this type of pollution particulates. Particulats can damage human health e.g. they increase the risk of heart disease and lung disease. Particulates can also reduce the amount of energy from the sun that reaches the earths surface. Scientists call this global dimming,  which is possible that it is affecting rainfall patterns.

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