They all use the same raw temperature data, and the issue is they make slightly different adjustments due to problems of urban heat islands and so on. (realclimate.org)
Global warming skeptics have increasingly become critical of adjustments to raw temperature data made by government climate agencies. (dailycaller.com)
In 2010, Judicial Watch obtained internal documents from NASA's Goddard Institute for Space Studies (GISS) related to a controversy that erupted in 2007 when Canadian blogger Stephen McIntyre exposed an error in NASA's handling of raw temperature data from 2000 - 2006 that exaggerated the reported rise in temperature readings in the United States. (judicialwatch.org)