Since 1979, polar-orbiting satellites have indirectly measured lower tropospheric temperatures. From time to time, questions have arisen concerning the accuracy of this global temperature data set. Wentz and Schabel (1998), for example, argued that the satellite data had not been properly adjusted for orbital decay. Yet, after accounting for such decay, trends in the satellite data continue to display no significant global warming since 1979. [See for yourself; plot the 1979-2000 MSU satellite data found in our World Temperatures Section.] This essentially flat trend in the lower troposphere stands in stark contrast to what is observed in various surface temperature data sets over this same time interval. [Again, see for yourself; plot the 1979-2000 surface temperature data from the Jones or GHCN databases found in our World Temperature Section.]
Gaffen et al. (2000) and Santer et al. (2000) have attempted to determine the reason for the satellite/surface temperature record discrepancy for the region of the tropics and for the entire globe, respectively. In examining the tropics, where Gaffen et al. note the difference between the two trends is most pronounced, no understanding of the difference could be discerned using sophisticated climate models. Similarly, Santer et al. (2000) utilized state-of-the-art computer models, but also could not explain the difference between these two temperature trends.
References
Comiso, J.C. 2000. Variability and trends in Antarctic surface temperatures from in situ and satellite infrared measurements. Journal of Climate 13: 1674-1696.
Gaffen, D.J., Santer, B.D., Boyle, J.S., Christy, J.R., Graham, N.E. and Ross, R.J. 2000. Multidecadal changes in the vertical temperature structure of the tropical troposphere. Science 287: 1242-1245.
Santer, B.D., Wigley, T.M.L., Gaffen, D.J., Bengtsson, L., Doutriaux, C., Boyle, J.S., Esch, M., Hnilo, J.J., Jones, P.D., Meehl, G.A., Roeckner, E., Taylor, K.E. and Wehner, M.F. 2000. Interpreting differential temperature trends at the surface and in the lower troposphere. Science 287: 1227-1232.
Wentz, F.J. and Schabel, M. 1998. Effects of orbital decay on satellite-derived lower-tropospheric temperature trends. Nature 394: 661-664.