NCPA - National Center for Policy Analysis

Global Warming Scientific Debate Continutes

August 13, 1998

Scientists have been puzzled by the discrepency between surface temperature readings that indicate a global warming trend of about one degree over the last century, and temperatures collected by satellite since 1979 that seem to show a slight cooling trend.

In a new study, Frank J. Wentz and Matthias Schabel, atmospheric physicists with Remote Sensing Systems, claim that because NASA's orbiting satellites lose altitude as they circle the globe, their temperature data is inaccurate.

  • Wentz and Schabel suggest that, factoring in these altitude drops, the planet has warmed 0.13 degrees per decade rather than declined by 0.09 degrees per decade as the satellite data seem to show.
  • Their new interpretation is agrees more closely with surface temperatures, but shows only about half as much warming.
  • However, the satellite data already agreed with surface temperatures in many regions, including the Northern Hemisphere, says John R. Christy of the University of Alabama.
  • And other corrections recently made, such as accounting for east-west drift of the satellites, showed a very small warming in the lower atmosphere, says Christy: close to zero and smaller than the revised data reported.

Wentz's and Schabel's conclusions are flawed, says analyst David Ridenour of the National Center for Public Policy Research:

  • Weather balloons corroboratethe satellite measurements showing no global, and they should differ if the satellite data were significantly off.
  • Researchers adjusted their data to account for "false cooling" due to declining satellite altitudes, but didn't adjust for "false warming" caused by other factors.
  • Also, they used adjusted data in their study instead of raw data, overstating the impact of satellite orbital decay.

Source: William K. Stevene, "As Debate Persists, New Study Confirms Atmospheric Warming," New York Times, August 13, 1998; Press Release "Study Challenging Validity of Satellite Data Flawed," August 13, 1998, National Center for Public Policy Research, 300 Eye Street, N.E., Suite 3, Washington, D.C. 20002, (202) 543-1286.


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