C13
History of our atmosphere
The earths early atmosphere was formed by volcanic activity
It probably consisted mainly of carbon dioxide.
As plants spread over the earth, the levels of oxygen in the atmosphere increased
Our evolving atmosphere
Photosynthesis by algae and plants decreased the percentage of carbon dioxide in the early atmosphere. this was when the formation of sedimentary rocks and fossil fuels took place.
Any ammonia and methane was removed by reactions with oxygen.
About 4/5ths of the atmosphere today is nitrogen.
Greenhouse gases
The amount of carbon dioxide in the earths atmosphere has risen in the recent past.
The vast majority of peer reviewed evidence shows that there were increased greenhouse gases from human activities.
Global Climate Change
Reducing green house gases in the atmosphere relies on reducing fossil fuels.
The economies of developed countries are based on energy that is obtained in fossil fuels, so changes would cost money.
Changes are needed because of the potential risks arising from global climate changes.
Atmospheric pollutants
When hydrocarbon fuels are burnt in a lot of air, the carbon and hydrogen in the fuel are completely oxidised
Sulfur impurities in fuels burn to form sulfur dioxide which can cause acid rain
Changing the conditions in which hydrocarbon fuels are burnt can change the products made.
In insufficient oxygen, poisonous carbon monoxide gas is formed
At the high temperatures in engines, nitrogen from the air reacts with oxygen to form oxides of nitrogen.