Another new paper disputes surface temperature record

by William Yeatman on June 8, 2004

in Science

Historical climate data that had previously been thought to exhibit a slight warming trend has come under fire in another newly published scientific srticle (see story in the last issue on the McKitrick and Michaels paper). The United States Historical Climatology Networks (USHCN) temperature database, the most widely used and highly respected database available for regional scale analysis in the U. S., has been shown to have significant biases toward higher temperatures that have apparently been overlooked in years past. This finding is evident despite the fact that the dataset had been previously adjusted for a variety of temperature discrepancies, ranging from missing temperature data to the transition from mercurial to electronic sensing equipment. Scientists Robert C. Balling Jr. and Shouraseni Sen Roy found in their recent study published in the Geophysical Research Letters (May 1, 2004) that the USHCN temperature data is considerably upward biased.

Using spatial entropy to estimate disorder in the pattern of temperature changes across the 1,221 USHCN climate monitoring stations, Balling and Roy found that some “questionable warming signals” existed at some stations. Spatial entropy is a measure of disorder or dissimilarity of the distribution of the USHCNs weather stations.

Continuing, “Stepwise multiple regression analyses were conducted with latitude, latitude squared, longitude, longitude squared, and elevation aspotential independent variables in explaining spatial variance in the temperature change values.” They found all of the independent variables to be highly significant with regards to the temperature increase, meaning that some bias must exist within the dataset.

The authors explained their results. “We find that over the (USHCN) network, the spatial entropy levels are significantly and positively related to the observed temperature trends suggesting that stations most unlike their neighbors in terms of temperature change tend to have a higher temperature trend than their neighbors.” Balling and Roy added, “One could conclude that the network still contains unproven warming signals possibly related to lingering urbanizations effects.”

They concluded the article by explaining, “While the developers of the United States Historical Climatology Network have made substantial efforts to eliminate effects of time of observation biases, changes in measuring equipment, station relocations, and urbanization, our results suggest that the adjusted records continue to contain any number of contaminants that increase the temperature trend (warm) at some stations.”

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