In 2007, McIntyre started auditing the various corrections made to temperature records, in particular those relating to the urban heat island effect. He discovered a discontinuity in some U.S. records in the Goddard Institute for Space Studies (GISS) dataset starting in January 2000. He emailed GISS advising them of the problem and within a couple of days GISS issued a new, corrected set of data and thanked McIntyre for "bringing to our attention that such an adjustment is necessary to prevent creating an artificial jump in year 2000". The adjustment reduced the average temperatures for the continental United States by about 0.15 °C during the years 2000-2006. Changes in other portions of the record did not exceed 0.03 °C; it made no discernible difference to the global mean anomalies.