First direct observation of the atmospheric CO2 year-to-year increase from space M. Buchwitz, O. Schneising, J. P. Burrows, H. Bovensmann, M. Reuter, 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 CO2 total vertical columns
from satellite observations
is predicted to improve this situation. Such an application however requires
very high accuracy and precision.
We report on retrievals of the column-averaged CO2 dry air mole fraction,
denoted XCO2, from the near-infrared nadir spectral radiance and
solar irradiance 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
global XCO2 obtained from
NOAA's CO2 assimilation system CarbonTracker
taking into account the spatio-temporal sampling and
altitude sensitivity of the satellite data.
We show that the measured CO2 year-to-year increase
agrees within about 1 ppm/year with CarbonTracker.
We also show that the latitude dependent
amplitude of the northern hemispheric CO2 seasonal
cycle agrees with CarbonTracker within about 2 ppm
with the retrieved amplitude being systematically larger.
The analysis demonstrates that it is possible using
satellite measurements of the CO2 total column
to retrieve information on the atmospheric CO2
on the level of a few parts per million.
Citation: Buchwitz, M., Schneising, O., Burrows, J. P., Bovensmann, H., Reuter, M., and Notholt, J.: First direct observation of the atmospheric CO2 year-to-year increase from space, Atmos. Chem. Phys., 7, 4249-4256, doi:10.5194/acp-7-4249-2007, 2007.