In June 2006, the satellite-borne lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) began its observations onboard CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations; Winker et al., 2007). This date is regarded the starting point of a unique long-term, global, 4-dimensional aerosol and cloud data set. The forthcoming missions ADM-Aeolus (Atmospheric Dynamics Mission; Stoffelen et al., 2005; Ansmann et al., 2006) of the European Space Agency ESA and EarthCARE (Earth Clouds, Aerosols, and Radiation Explorer) of ESA and the Japan Aerospace Exploration Agency JAXA (ESA, 2004), with their lidar instruments ALADIN (Atmospheric Laser Doppler Lidar Instrument) and ATLID (Atmospheric Lidar), respectively, will continue such kind of observations. It is expected that the long-term data set gained in this way will substantially improve our knowledge on the role of aerosols and clouds in the Earth's climate system.