#145 Effects of combustion of fossil fuels on CO2 level

Photosynthesis takes CO₂ out of the atmosphere and replaces it with O₂. Respiration and combustion both do the opposite: they use up O₂ and replace it with CO₂.

The equations are essentially the same, but reversed:

In order for the amount of CO2 in the atmosphere to remain stable, the rates of these processes need to be balanced. 

Processes that change the equilibrium (balance) include:

• cutting down forests (deforestation) – less photosynthesis
• combustion of fossil fuel (coal, oil and gas)
• increasing numbers of animals (including humans) – they all respire.

An increase in CO₂ levels in the atmosphere is thought to contribute to global warming. 

CO₂ forms a layer in the atmosphere, which traps heat radiation from the Sun. This causes a gradual increase in the atmospheric temperature which can:

• melt polar ice caps, causing flooding of low-lying land
• change weather conditions in some countries, increasing flooding or reducing rainfall and changing arable (farm) land to desert
• cause the extinction of some species that cannot survive at higher temperatures.