The Earth's atmosphere

4.7 billion years ago, the Earth was formed.

Volcanic activity released CO2 and heat, making up most of the atmosphere. Other greenhouse gases such as water vapour, CH4, N2 and NH3 ammonia are present in smaller amounts

Earth cools, water vapour condensed to form oceans. Carbonate precipitates were formed when CO2 dissolved and reacted with seawater. These precipitates got deposited as sediment. CO2 levels are reduced. → sediments + animal skeletons + high pressure = coal + limestone, which also reduced CO2 levels.

bacteria, algae and simple organisms began to populate oceans about 2.7 billion years ago. They photosynthesised, producing oxygen, and removing CO2. once a certain amount was present, other complex organisms began to populate Earth. Early organisms died out, unable to cope with the increased oxygen concentration.

As animals and plants died, their remains stayed heated in the Earth’s crust, forming fossil fuels. The carbon dioxide in their bodies (in the blood of animals and the biomass of plants due to respiration) was thus locked up.

methane reacted with oxygen to form water vapour and CO2, reducing its amount

ammonia reacted with oxygen to form water vapour and nitrogen, reducing its amount

nitrogen is very unreactive so has built up over time

now, the atmosphere is about 80% nitrogen and 20% oxygen, with traces of other gases

greenhouse gases maintain the earth’s temperature so life can be sustained.

the sun emits short and long wavelength radiation. the earth absorbs a portion of this, but also reflects longer wavelength radiation back to space. Some of this is absorbed by greenhouse gases in the atmopshere, which then re-radiate the wavelengths in all directions, including back to earth.

peer-reviewed evidence suggests that human activities will cause the Earth’s surface temperature to increase, but the global climate system is so complex that it’s difficult to model via extrapolation - extending a graph past collected data. This method assumes that the current trend will continue and that there is enough data at the present.

carbon footprint - the total amount of CO2 and other greenhouse gases emitted over the full life cycle of a product, service or event

Reducing carbon footprint:

• use biofuels - not burning fossil fuels reduced greenhouse gas emissions

• CCS - reduces CO2 emissions and takes CO2 from the open atmosphere, then liquifying it and storing it underground

• eating less beef - reduces demand which encourages farmers to stop rearing methane producing cows

• recycle more - reducing methane by reducing the waste microbes at landfill can decay

• tax polluting vehicles - reduces fossil fuel consumption and encourages people to invest in better alternatives

effects of global climate change:

• rising sea levels due to melting ice caps

• extinction, habitats under stress

• changes in the amount, timing and distribution of rainfall → migration?

• potential changes in the power and frequency of extreme weather, like tropical storms

fuel burning (combustion) is a major atmospheric pollutant.

most fuels contain carbon, hydrogen and potentially sulphur.

• sulphur impurities are oxidised to form sulphur dioxide

complete combustion - enough oxygen for all the carbon atoms in a fuel to burn (get oxidised), forming CO2 and water.

• CO2 contributes to greenhouse effect

incomplete combustion: NOT enough oxygen for all the carbon atoms in a fuel to burn, releasing less energy and other products:

• particulates: soot - solid carbon. a mixture of carbon and unburnt fuel, formed when large molecule hydrocarbons (fuels) get burnt in diesel engines and incomplete combustion occurs.

• carbon monoxide: produced because there’s lacking oxygen - carbon dioxide cannot be formed.

these can have a multitude of effects:

• particulates: global dimming (decrease in sunlight reaching earth) and lung problems in humans.

• carbon monoxide: replaces O2 in the blood, depriving the body and leading to cardiac arrest. colourless and odorless, making it hard to detect.

• sulphur: sulphur dioxide causes acid rain + respiratory issues

nitrogen is generally unreactive, but at high temperatures found in an engine, it may react with oxygen to form nitrous oxides, that cause acid rain and respiratory issues.