The objective of this research is to determine whether poorly sited long-term surface temperature monitoring sites have been adjusted in order to provide spatially representative independent data for use in regional and global surface temperature analyses. We present detailed analyses that demonstrate the lack of independence of the poorly sited data when they are adjusted using the homogenization procedures employed in past studies, as well as discuss the uncertainties associated with undocumented station moves. We use simulation and mathematics to determine the effect of trend on station adjustments and the associated effect of trend in the reference series on the trend of the adjusted station. We also compare data before and after adjustment to the reanalysis data, and we discuss the effect of land use changes on the uncertainty of measurement.

A major conclusion of our analysis is that there are large uncertainties associated with the surface temperature trends from the poorly sited stations. Moreover, rather than providing additional independent information, the use of the data from poorly sited stations provides a false sense of confidence in the robustness of the surface temperature trend assessments.

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CIRES and ATOC, University of Colorado, Boulder, Colorado

Department of Atmospheric Sciences, Texas A&M University, College Station, Texas

Desert Research Institute, Reno, Nevada

Illinois State Water Survey, Department of Natural Resources, Champaign, Illinois

Atmospheric Science, Colorado State University, Fort Collins, Colorado

Department of Meteorology, The Florida State University, Tallahassee, Florida

Departments of Agronomy and Earth & Atmospheric Sciences, Purdue University, West Lafayette, Indiana

Center for Satellite Applications and Research, NOAA/NESDIS, Camp Springs, Maryland

CIRA, Colorado State University, Fort Collins, Colorado

School of Natural Resources, University of Nebraska-Lincoln, Lincoln, Nebraska

Department of Atmospheric and Oceanic Science, University of Maryland, College Park, College Park, Maryland

Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina