HUNTSVILLE, AL (May 5, 2004) — A new study of global temperature data reports this week the discovery that significant global warming can be found by subtracting from the temperature record more cooling than was actually there.
“You can’t subtract more signal than is there, but that’s what they’ve done,” said Dr. Roy Spencer, a principal research scientist in the Earth System Science Center at The University of Alabama in Huntsville (UAH). “They’ve subtracted more than is actually there.”
The study in question, by Fu et al., is published this week in Nature. The authors claim to find significant atmospheric warming over the past 25 years when cooling that has taken place in the stratosphere during that time is removed from the tropospheric temperature data gathered by instruments aboard NOAA satellites.
The problem, says Spencer, is that the study uses a negative ³weighting” function that removes more stratospheric cooling than actually appears in the data, thus creating a spurious warming signal.
“Simply put, this method over corrects for stratospheric cooling,” said Dr. John Christy, a professor of atmospheric science at UAH and director of the ESSC. “We tried this same technique in the early 1990s but it didn’t work. Instead, Roy developed a method for accurately removing stratospheric temperatures from the data and we published that in 1992.”
Spencer and Christy were the first to use data from microwave sounding units aboard NOAA satellites to track global temperature trends. Over the past 13 years they have made several corrections to their dataset as different problems have been identified.
The satellite sensors, which have been in service since late November 1978, show a long-term lower atmosphere global warming trend of about 0.08 C (0.14 degrees Fahrenheit) per decade in the past 25 years. This trend has been corroborated by U.S., British and Russian studies comparing the satellite data to temperature data gathered by weather balloons.