This report illustrates and quantifies the unanticipated large uncertainty and differences in tropospheric temperature analyses within current global operational forecast systems and historical re-analysis products. Results reveal that regional patterns of uncertainty in seasonally averaged and daily atmospheric upper-air temperature analyses are related to the irregular distribution of in situ and satellite observations. There is less uncertainty in analysed temperature where in situ radiosonde observations are plentiful, primarily over developed nations in the Northern Hemisphere, and more uncertainty over regions that are observed primarily by satellites with fewer in situ temperature observations, including oceanic areas, the cryosphere, and developing nations. The results suggest that operational weather forecasting and climate monitoring would benefit from an improved global observing network, including additional in situ components. There is also a need for progress in data assimilation to extract more information from the wealth of current and future satellite observations.