 Soil moisture was recently added to the list of essential climate variables, ECVs, which are deemed essential for IPCC and UNFCCC needs and considered feasible for global observation. To create a consistent data record, multiple data sources including active and passive microwave observations in the low-frequency range should be used. Sensors such as C-band scatterometers on ERS and Metop satellites and multi-frequency radiometers can be used to cover a time period of more than 30 years. The best approach for fusing different satellite data sets is to merge level 2 soil moisture data derived from individual satellite data records, which has already been demonstrated in the WACMOS project and will be further improved in the Climate Change Initiative Program of ESA. This article was authored by W. Wagner, W. Derigo, R. Dejeu and others. We are article.tv, links in the description below.