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Damage to the environment

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The atmosphere has not always been the same. It has been much the same, but nevertheless now contains more nitrogen and oxygen, and less carbon dioxide, than it did when the earth first formed. Recently, the addition of greenhouse gases such as carbon dioxide from burning fossil fuels has lead to global warming.

It is difficult to predict, even by using computer models, exactly what the mean temperature of the Earth will be in the future. However it seems sensible to limit global warming and protect the environment, through sustainable development and by reducing waste, wherever possible.

Evolution of the atmosphere

Scientists believe that the Earth was formed about 4.5 billion years ago. Its early atmosphere was probably formed from the gases given out by volcanoes. It is believed that there was intense volcanic activity for the first billion years of the Earth's existence.

The early atmosphere was probably mostly carbon dioxide, with little or no oxygen. There were small quantities of water vapour, ammonia and methane. As the Earth cooled down, most of the water vapour condensed and formed the oceans.

Changes in the atmosphere

So how did the proportion of carbon dioxide in the atmosphere go down, and the proportion of oxygen go up?

The proportion of oxygen went up because of photosynthesis by plants.

The proportion of carbon dioxide went down because:

it was locked up in sedimentary rocks, such as limestone, and in fossil fuels
it was absorbed by plants for photosynthesis
it dissolved in the oceans

The burning of fossil fuels is adding carbon dioxide to the atmosphere faster than it can be removed. This means that the level of carbon dioxide in the atmosphere is increasing.

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