Understanding and predicting of atmospheric temperature and water vapor variations is a key issue for characterizing global change. To precisely determine the current and future variations on a global scale, accurate atmospheric observations with satellites
are indispensable. We introduce an innovative and very precise satellite based atmospheric observation technique, which became operational during the recent years, pioneered also by the work of GFZ technicians and scientists: GNSS (Global Navigation
Satellite System) Radio Occultation (RO). The technique is based on the influence of the Earth’s atmosphere on the propagation of navigation signals (L-Band, 1.2 and 1.5 GHz). A key parameter for this influence is the bending angle of the signal path
from the transmitting navigation to the receiving Low Earth Orbiting (LEO) satellite, which depends on atmospheric temperature and water vapor. The GNSS RO method is currently applied aboard several LEO satellites, as GRACE, TerraSAR-X, TanDEM-X,
COSMIC and Metop. We also present recent scientific GFZ results related to the characterization of global atmospheric variations using the world-wide unique long-term GNSS RO data set from the GFZ geoscience satellite CHAMP (2000-2010). Hereby, tropopause temperature and altitude properties, precisely derived from the GNSS RO data, are also used to reveal even very small variations of the global atmosphere.