text: John Christy of the University of Alabama at Huntsville, who with his colleague Roy Spencer compiles the satellite temperature record, commented that Santer's "model shows that increasing tropopause heights are due in good measure to human factors for 1979-99. However, the real world shows a huge tropospheric temperature spike due to the 1997-98 El Nino which then tilts the tropopause height trend upward. So what causes the height increase in the model and in the data are likely two different causes."