Figure 6: Satellite Microwave Sounding Unit, MSU, measurements of global lower tropospheric temperatures between latitudes 83 N and 83 S from 1979 to 1997 (17,18). Temperatures are monthly averages and are graphed as deviations from the mean temperature for 1979 to 1996. Linear trend line for 1979 to 1997 is shown. The slope of this line is minus 0.047 ºC per decade. This record of measurements began in 1979.