John Christy and Roy Spencer of the University of Alabama published a series of papers starting about 1990 that implied the troposphere was warming at a much slower rate than the surface temperature record and climate models indicated Spencer and Christy (1992). One early version of their data even showed a cooling trend (Christy et al. 1995).Several groups of scientists began looking closely at this discrepancy. With so many other pieces of evidence indicating warming, it seemed unlikely that the troposphere would not be warming. Errors were discovered in the methods the UAH group used to adjust the data.To understand what was wrong: The satellites must pass over the same spot on Earth at the same time each day to get a temperature average. In reality the time the satellite passes drifts slightly as the orbit slowly decays. To compensate for this and other orbital changes a series of adjustments must be applied to the data.
Argument evaporates According to Santer, the only group to previously analyze satellite data on the troposphere -- the lowest layer in Earth's atmosphere -- was a research team headed by Roy Spencer from University of Alabama in 1992."This was used by some critics to say 'We don't believe in climate models, they're wrong,'" Santer told LiveScience. "Other people used the disconnect between what the satellites told and what surface thermometers told us to argue that the surface data were wrong and that earth wasn't really warming because satellites were much more accurate."The Alabama researchers introduced a correction factor to account for drifting in the satellites used to sample Earth's daily temperature cycles.But in another Science paper published today, Carl Mears and Rank Wentz, scientists at the California-based Remote Sensing Systems, examined the same data and identified an error in Spencer's analysis technique.After correcting for the mistake, the researchers obtained fundamentally different results: whereas Spencer's analysis showed a cooling of the Earth's troposphere, the new analysis revealed a warming.Using the analysis from Mears and Wentz, Santer showed that the new data was consistent with climate models and theories."When people come up with extraordinary claims -- like the troposphere is cooling -- then you demand extraordinary proof," Santer said. "What's happening now is that people around the world are subjecting these data sets to the scrutiny they need."