An Accounting of the Observed Increase in Oceanic and Atmospheric CO2 and the Outlook for the Future

an accounting of the Observed increase in Oceanic and atmospheric cO 2 and an Outlook for the Future abStr act.Observations of CO 2 accumulation in the atmosphere and ocean show that they are approximately equal to the total amount emitted by burning of fossil fuels since 1850.A mass balance calculation is carried out with ocean uptake satisfying two observed constraints, and with net terrestrial emissions as the remainder.The calculation illustrates that before 1940, net terrestrial emissions were positive, and have been negative since then, making their cumulative contribution in 2008 rather small.The overall evidence strongly suggests that the increase of CO 2 in the atmosphere is 100% due to human activities, and is dominated by fossil fuel burning.Some simple projections of atmospheric CO 2 , and therefore also of surface pCO 2 for most of the ocean, are made with plausible future scenarios of fossil fuel emissions, only taking into account features of the carbon cycle that are quite well established. ObSerVed atmOSpheric cO 2 OVer the laSt thOuSaNd YearSDavid Keeling was the first to make very accurate measurements of carbon dioxide (CO 2 ) in air (Keeling, 1958(Keeling, , 1960;;Pales and Keeling, 1965).His innovations were the extensive use of carefully calibrated reference gas mixtures with a continuously operating infrared (IR) spectrometer, and the very accurate manometric calibration of each reference gas.The measurements were backed up from the start by independent grab samples of air in flasks, one pair or triplicate per week, obtained near the air intake of the IR analyzer.The flasks were all sent to Scripps Institution of Oceanography for analysis.The instruments have evolved since then, but not the principles of calibration and comparison to independent methods.These principles are still at the core of the present international global network of atmospheric greenhouse gas measurements coordinated by the United Nations World Meteorological Organization in its Global Atmosphere Watch (GAW) Programme.The new methods enabled Keeling's discovery b Y p i e t e r ta N S Oceanography Vol.22,No.4 26