Gas naturally present in the atmosphere, accounting for approximately 0.036% of all of the atmospheric gases, and also emitted from the burning of fossil fuels and biomass, land use changes, and other industrial processes. It is one of the main greenhouse gases and is used as a reference to the other ones.
Fossil fuels
Fuels such as oil, natural gas, and mineral coal – fossilized plant residues – that are buried in the Earth's crust and reached their present state through chemical reactions over long periods of time. They are produced by the continuous decomposition of organic...