When future generations try to understand how the world got carried away around the end of the 20th century by the panic over global warming, few things will amaze them more than the part played in stoking up the scare by the fiddling of official temperature data. Steven Goddards US blog Real Science [shows] how shamelessly manipulated has been one of the worlds most influential climate records, the graph of US surface temperature records published by the National Oceanic and Atmospheric Administration (NOAA). Goddard shows how, in recent years, NOAAs US Historical Climatology Network (USHCN) has been adjusting its record by replacing real temperatures with data fabricated by computer models. The effect of this has been to downgrade earlier temperatures and to exaggerate those from recent decades, to give the impression that the Earth has been warming up much more than is justified by the actual data. In several posts headed Data tampering at USHCN/GISS, Goddard compares the currently published temperature graphs with those based only on temperatures measured at the time. These show that the US has actually been cooling since the Thirties, the hottest decade on record; whereas the latest graph, nearly half of it based on fabricated data, shows it to have been warming at a rate equivalent to more than 3 degrees centigrade per century.