New paper disputes surface temperature record

by William Yeatman on May 27, 2004

in Science

In a new article published in Climate Research, Ross McKitrick of the University of Guelph and Patrick J. Michaels of the University of Virginia have found, through statistical analysis, that the Intergovernmental Panel on Climate Change’s temperature data contains a net warming bias due to socioeconomic effects that were not removed properly from the IPCC’s records. 

In the article, entitled “A test of correlations for extraneous signals in gridded surface temperature data,” McKitrick and Michaels obtained monthly surface temperature records from 1979 to 2000 from 218 individual stations in 93 countries.  They regressed this temperature data with regards to local climate, as well as indicators of local economic activity (such as income, GDP growth rates, and coal use) and data quality.  The authors found that the spatial pattern of trends is shown to be significantly correlated with non-climatic factors such as economic activity and various sociopolitical effects.  The process was repeated on the corresponding IPCC gridded data.  Despite the IPCC’s attempt to remove these non-climatic variables, McKitrick and Michaels found that similar correlations do exist and that the IPCC’s data was biased in favor of global warming.

The article explained that, “[The apparent climate biases] reflect the influence of many things, including a complex blend of local economic and social factors.  Some of these exert an indirect influence on local temperatures but have nothing to do with the global climate, while others have nothing to do with temperature at all but instead affect data quality control.”  Controlling for the non-climatic variables would result in a “noticeably lower” temperature change, McKitrick and Michaels observed.

Moreover, “Attempts to identify the magnitude of a global ‘greenhouse’ climate signal on surface data without properly removing the extraneous biases risks exaggerating the perceived influence of atmospheric CO2 levels.”

The article concluded, “The results of this study support the hypothesis that published temperature data are contaminated with non-climatic influences that add up to a net warming bias, and that efforts should be made to properly quantify these effects.”

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