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A Warming Bias in the U.S. Temperature Record???
Balling Jr., R.C. and Idso, C.D. 2002. Analysis of adjustments to the United States Historical Climatology Network (USHCN) temperature database. Geophysical Research Letters 10.1029/2002GL014825.

What was done
The authors analyzed and compared the trends of six different temperature databases for the conterminous United States over the period 1979-2000. These databases comprised: (1) the unadjusted temperature data of the United States Historical Climatology Network (RAW), (2) the RAW data adjusted for (a) time of observation biasing, (b) changes to the new maximum/minimum temperature system equipment, (c) station history, including other instrument adjustments, and (d) an interpolation scheme for estimating missing data from nearby highly correlated station records (FILNET), (3) essentially the FILNET data adjusted for urbanization effects (URB-ADJ), (4) the updated dataset developed by Jones (1994) of the University of East Anglia (IPCC), (5) the satellite-based lower-tropospheric temperature dataset (MSU2LT), and (6) the radiosonde (balloon-based) temperature data that comprised "the surface reading taken the moment the balloon is launched," which "typically occurs near 1.5 m above the surface, which is near the shelter heights used in the USHCN data set" (SONDE).

What was learned
In comparing the difference between the FILNET and RAW temperature trends, Balling and Idso found a nearly monotonic increase of over 0.05C per decade, which they found to be highly significant at the 0.0001 level of confidence. In addition, they found that "the trends in the unadjusted temperature records [were] not different from the trends of the independent satellite-based lower-tropospheric temperature record or from the trend of the balloon-based near-surface measurements."

What it means
In the words of the two Arizona State University Office of Climatology researchers, the adjustments that were being made to the raw USHCN temperature data were "producing a statistically significant, but spurious, warming trend" that "approximates the widely-publicized 0.50C increase in global temperatures over the past century." It would thus appear that in this particular case of "data-doctoring," the cure was much worse than the disease. And it likely still is! In fact, it would appear that the cure may actually be the disease.

Unfortunately, it also appears that the disease has spread, both far and wide, and become a global pandemic; for Klotzbach et al. (2009) have recently found that for the updated period of 1979-2008, "there have, in general, been larger linear trends in surface temperature data sets such as the NCDC [the U.S. National Climate Data Center] and HadCRUT3v [University of East Anglia] surface data sets when compared with the [satellilte-derived] lower-tropospheric data sets." And they note that Santer et al. (2005) have said that such could occur "if the surface warming had been over-estimated by 0.05C per decade in the IPCC data," which is the very same difference that Balling and Idso obtained.

Perhaps, therefore, it is not only the Climatic Research Unit of the University of East Anglia that needs to have the validity of its temperature adjustments audited. Some institutions in the United States may be deserving of such treatment as well. It may be a hard pill for some of them to swallow; but with so much riding on the outcome -- and the health of the planet hanging in the balance -- the treatment would surely be worth it.

Jones, P.D. 1994. Hemispheric surface air temperature variations: A reanalysis and an update to 1993. Journal of Climate 7: 1794-1802.

Klotzbach, P.J., Pielke Sr., R.A., Pielke Jr., R.A., Christy, J.R. and McNider, R.T. 2009. An alternative explanation for differential temperature trends at the surface and in the lower troposphere. Journal of Geophysical Research 114: 10.1029/2009JD011841.

Santer, B.D., Wigley, T.M.L., Mears, C., Wentz, F.J., Klein, S.A., Seidel, D.J., Taylor, K.E., Thorne, P.W., Wehner, M.F., Gleckler, P.J., Boyle, J.S., Collins, W.D., Dixon, K.W., Doutriaux, C., Free, M., Fu, Q., Hansen, J.E., Jones, G.S., Ruedy, R., Karl, T.R., Lanzante, J.R., Meehl, G.A., Ramaswamy, V., Russell, G. and Schmidt, G.A. 2005. Amplification of surface temperature trends and variability in the tropical atmosphere. Science 309: 1551-1556.

Reviewed 16 December 2009