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6.4.1.1. Sources of Atmospheric CO2

Sources of atmospheric CO2 can today be divided into two groups: natural and anthropogenic. Natural sources include the respiration of animals (60Gt per annumFigures quoted here from IPCC (1995) are the best estimates for present day annual carbon fluxes) and the surface ocean (90Gt per annum) (Schimel et al., 1995). Anthropogenic sources include the combustion of fossil fuels (power stations and transport) and cement production (5.5Gt per annumEstimates for anthropogenic sources of CO2 are usually accompanied with ranges of uncertainty. For example, IPCC (1995) estimate emissions from fossil fuels and cement production to be 5.5Gt  0.5Gt.)and land-use changes (mainly deforestation) (1.6Gt per annum)