Atmos. Chem. Phys. Discuss., 7, 6719-6735, 2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
First direct observation of the atmospheric CO2 year-to-year increase from space
M. Buchwitz, O. Schneising, J. P. Burrows, H. Bovensmann, and J. Notholt
Institute of Environmental Physics (IUP), University of Bremen FB1, Bremen, Germany

Abstract. The reliable prediction of future atmospheric CO2 concentrations and associated global climate change requires an adequate understanding of the CO2 sources and sinks. The sparseness of the existing surface measurement network limits current knowledge about the global distribution of CO2 surface fluxes. The retrieval of the CO2 total vertical column from satellite observations is predicted to improve this situation. Such an application however requires very high accuracy and precision on the order of 1% (4 ppm) or better. We report on retrievals of the column-averaged CO2 dry air mole fraction, denoted XCO2, from the measurements of the SCIAMACHY satellite instrument between 2003 and 2005. We focus on northern hemispheric large scale CO2 features such as the CO2 seasonal cycle and show – for the first time – that the atmospheric annual increase of CO2 can be directly observed using satellite measurements of the CO2 total column. The satellite retrievals are compared with the global assimilation system CarbonTracker and with local surface CO2 measurements based on weekly flask sampling. We show that the year-to-year CO2 increase as determined from the satellite data agrees with the reference data within about 1 ppm/year. We also show that the CO2 seasonal cycle over northern hemispheric low and mid latitudes can be retrieved with a precision of about 2 ppm. The results presented here demonstrate that it is possible using satellite measurements to retrieved information on the atmospheric CO2 on the level of a few parts per million.

Citation: Buchwitz, M., Schneising, O., Burrows, J. P., Bovensmann, H., and Notholt, J.: First direct observation of the atmospheric CO2 year-to-year increase from space, Atmos. Chem. Phys. Discuss., 7, 6719-6735, doi:10.5194/acpd-7-6719-2007, 2007.
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