All values in billion tonnes of carbon per year (GtC/yr), for the globe. For values in billion tonnes of carbon dioxide (CO2) per year, multiply the numbers below by 3.664.
1 billion tonnes C = 1 petagram of carbon (10^15 gC) = 1 gigatonne C = 3.664 billion tonnes of CO2
The methods used to estimate the historical fluxes presented below differ from the carbon budget presented from 1959 onwards. For example, the atmospheric growth and ocean sink do not account for year-to-year variability before 1958.
Uncertainties: see the original papers for uncertainties
Fossil fuel combustion and cement production emissions:
Gilfillan, D., Marland, G., Boden, T. and Andres, R.: Global, Regional, and National Fossil-Fuel CO2 Emissions, available at: https://energy.appstate.edu/CDIAC, last access: 27 September 2019, 2019.
Land-use change emissions as average of two bookkeeping models:
Houghton, R. A. and Nassikas, A. A.: Global and regional fluxes of carbon from land use and land cover change 1850-2015, Global Biogeochemical Cycles, 31, 456-472, 2017; Hansis, E., Davis, S. J., and Pongratz, J.: Relevance of methodological choices for accounting of land use change carbon fluxes, Global Biogeochemical Cycles, 29, 1230-1246, 2015.
Atmospheric CO2 growth rate:
Joos, F. and Spahni, R.: Rates of change in natural and anthropogenic radiative forcing over the past 20,000 years, Proceedings of the National Academy of Science, 105, 1425-1430, 2008.
The ocean CO2 sink is the average of the two diagnostic ocean models:
DeVries, T.: The oceanic anthropogenic CO2 sink: Storage, air-sea fluxes, and transports over the industrial era, Global Biogeochemical Cycles, 28, 631-647, 2014; and Khatiwala, S., Tanhua, T., Mikaloff Fletcher, S. E., Gerber, M., Doney, S. C., Graven, H. D., Gruber, N., McKinley, G. A., Murata, A., Rios, A. F., and Sabine, C. L.: Global ocean storage of anthropogenic carbon, Biogeosciences, 10, 2169-2191, 2013.
The land sink is the average of several dynamic global vegetation models that reproduce the observed mean total land sink of the 1990s.
The budget imbalance is the sum of emissions (fossil fuel and industry + land-use change) minus (atmospheric growth + ocean sink + land sink); it is a measure of our imperfect data and understanding of the contemporary carbon cycle.