Seasonal snow is a main element of the global water cycle and climate system. Due to its strong influence on the radiation and energy balance, changes in snow extent tend to amplify climate fluctuations. Terrestrial snow covers up to 50 million km2 of the Northern Hemisphere in winter and is characterized by high spatial and temporal variability. Therefore satellite observations provide the only means for timely and complete observations of the global snow cover. The recently published 2013 IPCC Working Group 1report identifies a clear trend of decrease in seasonal snow extent during the recent decades. The importance of accurate data on the global snow cover has been addressed in the WCRP-CliC Workshop and "WCRP Grand Challenges and the Cryosphere in a Changing Climate", held in Tromsö, 16-18 Oct. 2013. In order to improve the knowledge of the temporal dynamics and physical properties of snow as a component of the coupled climate system, the need to "produce better global-scale datasets of snow cover, SWE, and snow thermal properties by drawing together local and remote sensing observations" has been identified as an important goal". Also in the WMO Global Cryosphere Watch Workshop in January 2013 the need of evaluating and consolidating snow products based on different satellite sensors and retrieval methods was identified.