The University of Alabama in Huntsville processes microwave sounder data into monthly temperatures of four atmospheric layers, from the lower troposphere to the lower stratosphere, since December 1978.The four-layer breakdown is valuable because it reveals how the atmosphere responds to greenhouse gas increases. Theory predicts that the troposphere should warm while the stratosphere cools, a fingerprint of human-caused climate change. The UAH record has documented both trends, providing evidence that the observed changes are not due to natural solar variability alone. It also helps scientists study phenomena like the El Niño–Southern Oscillation, volcanic eruptions, and the effects of ozone depletion, all of which leave distinct signatures in different atmospheric layers.
The record was pioneered by John Christy and Roy Spencer at UAH, who published their first results in 1990. They developed the methodology for converting raw microwave data into atmospheric temperatures, and the dataset has been maintained and refined by their team ever since.
The challenge is maintaining consistency over decades, as satellites age, drift in their orbits, and are replaced by new instruments with slightly different characteristics. The UAH team applies corrections for these effects, using overlapping observations from successive satellites to calibrate the record. The result is a time series of monthly global and regional temperatures that is continuously updated and made freely available to the scientific community.
The UAH record is used by climate scientists to validate climate models, monitor the rate of global warming, and study atmospheric circulation changes, and it is frequently cited in assessments by the Intergovernmental Panel on Climate Change.
The satellite instruments that feed this record were originally designed for weather forecasting, not climate monitoring, and their data has been reprocessed multiple times as scientists discovered subtle errors—such as the cooling effect of the satellites' own orbital decay—that initially masked the true warming trend.













