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Orbital Effects on Satellite Temperatures
Reference
Wentz, F.J. and Schabel, M. 1998. Effects of orbital decay on satellite-derived lower-tropospheric temperature trends. Nature 394: 661-664.

What was done
Since 1979, a series of polar-orbiting satellites have indirectly measured lower tropospheric temperatures. After passing a series of rigorous quality control tests, the data from these satellites indicate that lower tropospheric temperatures have been cooling at a rate of 0.05C per decade. However, the author's of this article claim that the satellite data have not been properly adjusted for the confounding effect of satellite orbital decay, which they then attempt to do.

What was learned
By means of a series of statistical and model analyses, the authors computed the effect of orbital decay on the satellite temperatures, finding that the magnitude of the effect is heightened during periods of increased solar activity. When comparing their orbital decay corrected results with what they claim to be non-corrected results, the authors find that the lower troposphere may have warmed by 0.07C per decade since 1979. Noting that this trend is similar to the surface warming experienced over the same time period, as well as more compatible with the slight warming trend of the middle troposphere, they conclude that their results are likely to be more correct than what the satellite data were previously believed to have shown.

What it means
The publication of this paper will lead to numerous claims and counter-claims in both the popular media and the scientific literature. Indeed, the process began even before the paper's appearance in print, as the very next day produced a commentary about it in the pages of Science (see our web site's first Editorial Commentary). Although the results appear reasonable, it is far too early to draw definitive conclusions. The paper's ultimate impact (and correctness) may not be known for years.

Reviewed 15 September 1998