Global Carbon Dioxide Budget
Major Review Paper

In a special issue of Science in February 1993, which focused on evolution of atmospheres, a USGS geochemist wrote a major review paper on the global carbon dioxide(CO2) budget. The paper by Eric Sundquist describes the chemical exchanges among atmosphere, oceans, land surface, rocks, and biota that act to control CO2 levels in the atmosphere. The article indicates that the major problem associated with determining the CO2 budget is that recently and during the last deglaciation large amounts of CO2 appear to have been taken up by an as yet unidentified terrestrial reservoir. It points out that the increase in atmospheric CO2 during the last deglaciation was comparable in magnitude to the recent historical increase, but cautions that an important difference is the rapidity of the recent increase in CO2 levels. Also the oceans were a gradual source of CO2 during the deglaciation, but in modern times they have become a rapid net sink. The result of the uncertainty about the global carbon budget is that predictions of future levels of atmospheric CO2 (given any future scenario of fossil fuel use) are highly uncertain.

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For additional information and references, see the project description, Carbon Fluxes in Hydrologic and Geologic Processes , or contact Eric Sundquist, esundqui@usgs.gov