February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 10, NUMBER 4, APRIL 1997
SATELLITE TEMPERATURE TREND
Satellite measurements of global
temperature available since 1979 show a slight cooling trend, while the record
based on thermometers at ground level indicate warming over the same period.
This apparent discrepancy has fueled debate over the existence of global warming
in recent decades. In the September 1996 issue of the Journal of Climate,
James Hurrell and Kevin Trenberth discussed how the two records measure related
but different physical properties, yielding different perspectives on the same
events. (See PROF. PUBS./OF GEN. INTEREST, Feb. 1997.)
A new study by the same authors suggests that the satellite record contains
downward jumps that are artifacts of the instruments used, resulting from the
need to merge data collected by different satellites into a single record. The
corrected record would show a slight warming, as do surface measurements. (See
PROF. PUBS./OF GEN. INTEREST, this Global Climate Change Digest issue--Apr.
This argument is rejected by John Christy, the scientist who maintains the
satellite record. He says the satellite temperatures compare well with those
measured by balloons in the middle atmosphere, and that the jumps in the data
found by Hurrell and Trenberth reflect real changes in the atmosphere. His
comments and those of other scientists are discussed in Science News (p.
156, Mar. 15, 1997). See also New Scientist (p. 18, Mar. 15), and Global
Environ. Change Rep. (p. 4, Mar. 14).
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