Scientific Robustness Of The University Of Alabama At Huntsville MSU Data
By Dr. Roger Pielke Sr.
As a result of the persistent, but incorrect (often derogatory) blog posts and media reports on the robustness of the University of Alabama MSU temperature data, I want to summarize the history of this data analysis below. John Christy and Roy Spencer lead this climate research program.
The ad hominem presentations on this subject include those from the weblog Skeptical Science who have sections titled
If this weblog intends, as they write, to contribute to
Explaining climate change science & rebutting global warming misinformation
they certainly have failed in this effort, with respect to the outstanding research that Christy and Spencer have accomplished.
To summarize specifically the UAH MSU dataset, it has gone through about 9 revisions (A, B, C, D, 5.0, 5.1, 5.2, 5.3, 5.4 – some listed in CCSP 1.1.) Two of the revisions involved changes Jim Wentz of RSS spotted, but the other seven were ones John Chrsity and Roy Spencer discovered (i.e. major ones like the spurious warming due to a change in the sensor when the satellite went in and out of sunlight).
Such corrections are what happens in the normal course of science when you are the first to build the data set and discover issues as time goes on, especially when a satellite goes through a calibration shift. Their data are publicly available and their methods published in a diverse range of peer-reviewed journals.
A example of their reporting on a correction and acknowledging who found it (in this case Jim Wentz) is written in the article
Christy, J. R. and R. W. Spencer, 2005: Correcting Temperature Data Sets. 11 November 2005: 972. Science. DOI:10.1126/science.310.5750.972
Text from their article includes [highlight added]
“We agree with C. Mears and F. J. Wentz (“The effect of diurnal correction on satellite-derived lower tropospheric temperature,” 2 Sept., p. 1548; published online 11 Aug.) that our University of Alabama in Huntsville (UAH) method of calculating a diurnal correction to our lower tropospheric (LT) temperature data (v5.1) introduced a spurious component. We are grateful that they spotted the error and have made the necessary adjustments. The new UAH LT trend (v5.2, December 1978 to July 2005) is +0.123 K/decade, or +0.035 K/decade warmer than v5.1. This adjustment is within our previously published error margin of ± 0.05 K/decade.”
I also reported on an independent check on the robustness of the UAH MSU analyses in my post
where I reported
In order to further examine the robustness of the Christy and Spencer analyses, in 2006 I asked Professor Ben Herman, who is an internationally well-respect expert in atmospheric remote sensing, to examine the Christy and Spencer UAH MSU and the Wentz and Mears RSS MSU data analyses. He worked with a student to do this and completed the following study
Randall, R. M., and B. M. Herman (2007), Using Limited Time Period Trends as a Means to Determine Attribution of Discrepancies in Microwave Sounding Unit Derived Tropospheric Temperature Time Series, J. Geophys. Res., doi:10.1029/2007JD008864
which includes the finding that
“Comparison of MSU data with the reduced Radiosonde Atmospheric Temperature Products for Assessing Climate radiosonde data set indicates that RSS’s method (use of climate model) of determining diurnal effects is likely overestimating the correction in the LT channel. Diurnal correction signatures still exist in the RSS LT time series and are likely affecting the long-term trend with a warm bias.”
The plot of the lower tropospheric temperature analysis, as obtained from the MSU data, for the RSS and UAH groups are shown below. The degree of correspondence between them is another check on the value of both data sets in assessing long-term variations in the global averaged lower tropospheric temperatures.
The bottom line conclusion is that the statements made by Kevin Trenberth, John Abraham, and Peter Gleick in
Unfortunately this is not the first time the science conducted by Roy Spencer and colleagues has been found lacking. Spencer, a University of Alabama, Huntsville, climatologist, and his colleagues have a history of making serious technical errors in their effort to cast doubt on the seriousness of climate change. Their errors date to the mid-1990s, when their satellite temperature record reportedly showed the lower atmosphere was cooling. As obvious and serious errors in that analysis were made public, Spencer and Christy were forced to revise their work several times and, not surprisingly, their findings agree better with those of other scientists around the world…
are grossly incorrect and a retraction and a correction by Trenberth, Abraham and Gleick is appropriate. Similarly, weblogs such as Skeptical Science, if they want to move the debate on the climate issues forward, need to move towards a more constructive approach.
I’d like to add this from Dr. John Christy, from a comment he left on WUWT in this thread. – Anthony
Some clarifications are needed. The orbital decay effect was discovered by Wentz around 1997 which induced a spurious cooling effect on one of our microwave satellite products (lower troposphere) but not the others. However, most people forget that at the same time Roy and I discovered an “instrument body effect” in which the observed Earth-view temperature is affected by the temperature of the instrument itself, leading to spurious warming (Christy et al. 1998, 2000). This effect counteracted about 75 percent of the orbital decay cooling effect – so the net effect of the two together was almost a wash (a point rarely acknowledged.)
In 2005, Wentz and Mears discovered an error in the equation we used for the diurnal correction in one of our products (again, lower troposphere) which we quickly corrected and then published a “thank you” to Wentz and Mears in Science for their cleverness in spotting the error with an update on what the magnitude of the error was. Again, the magnitude of this error was small, being well within our previously published error estimates for the global trend. (Note that we were first to discover the diurnal drift problem back in the 1990s and initiated various corrections for it through the years.)
Roy and I were the first to build climate-type global temperature datasets from satellite microwave sensors, so we learned as we went – and were aided by others who read our papers and checked our methods. My latest papers continue to investigate error issues of our products and of the products of others.
The review of my one publication in Remote Sensing last year was done quite professionally and it was clear to me and my co-authors that the referees chosen to review the paper were specifically knowledgeable of the various satellite, radiosonde and statistical issues, leading to some substantial and useful revisions.
Kevin Trenberth was my MS and PhD graduate adviser at Univ. of Illinois.