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.
Entry into force
Intergovernmental agreements, including protocols and amendments, are not legally valid until ratified by a certain number of countries. For the UNFCCC creation, it took 50 countries; as for ratifying the Kyoto Protocol, at least 55 countries were required...