Sensitivity studies for space-based global measurements of atmospheric carbon dioxide

Carbon dioxide (CO₂) is well known as the primary forcing agent of global warming. Although the climate forcing due to CO₂ is well known, the sources and sinks of CO₂ are not well understood. Currently the lack of global atmospheric CO₂ observations limits our ability to diagnose the global carbon budget (e.g., finding the so-called "missing sink") and thus limits our ability to understand past climate change and predict future climate response. Space-based techniques are being developed to make high-resolution and high-precision global column CO₂ measurements. One of the proposed techniques utilizes the passive remote sensing of Earth's reflected solar radiation at the weaker vibration-rotation band of CO₂ in the near infrared ( ~1.57 μ m). We use a line-by-line radiative transfer model to explore the potential of this method. Results of sensitivity studies for CO₂ concentration variation and geophysical conditions (i.e., atmospheric temperature, surface reflectivity, solar zenith angle, aerosol, and cirrus cloud) will be presented. We will also present sensitivity results for an O₂ A-band ( ~0.76 μ m) sensor that will be needed along with CO₂ to make surface pressure and cloud height measurements.