There is a general agreement among the climate scientists that the Earth’s global average surfaceair temperature is now increasing at rates that are without precedent during the last 100 years. Different scales researches to the temperature of surface ground and upper air are the prerequisite for adapting the environment. Microwave Sounding Units (MSU/AMSU) on board NOAA polar orbiting satellites have provided temperatures of deep layers of the global atmosphere since 1978. After corrections such as calibration errors, orbital decay, and diurnal drift, MSU/AMSU longterm data for the upper air have become one of the best references, together with radiosonde observations and reanalysis data. This article elaborates the methods of calibrations, error corrections and merging from different satellites of MSU, and the advancement in the research of the longterm trend.