"In short, it wasn't a big deal. The changes were not, as described by DailyTech.com and repeated by the Wall Street Journal, "truly astounding." There was a legitimate, small mistake that NASA, when notified, quickly corrected. End of story."
NASA Revisions Create a Stir in The Blogosphere, Washington Post
"NASA has slightly revised its record of average annual temperatures in the United States since 2000 -- modifications that researchers say are insignificant but that some conservative commentators and bloggers have seized upon to assert that global warming has been hyped as a problem. The revisions, which were first posted on the Web site of NASA's Goddard Institute for Space Studies, stemmed from an error noticed by Canadian blogger and global warming skeptic Stephen McIntyre. James Hansen, director of the institute, said McIntyre brought the error to the institute's attention, and the error was corrected."
"But the revisions have been seized on by conservative Americans, including firebrand radio host Rush Limbaugh, as evidence that climate change science is unsound. Said Limbaugh last Thursday: "What do we have here? We have proof of man-made global warming. The man-made global warming is inside NASA ... is in the scientific community with false data." However Stephen McIntyre, who set off the uproar, described his finding as a "a micro-change. But it was kind of fun."
1934 and all that, RealClimate.org
"Another week, another ado over nothing. Last Saturday, Steve McIntyre wrote an email to NASA GISS pointing out that for some North American stations in the GISTEMP analysis, there was an odd jump in going from 1999 to 2000. On Monday, the people who work on the temperature analysis (not me), looked into it and found that this coincided with the switch between two sources of US temperature data. There had been a faulty assumption that these two sources matched, but that turned out not to be the case. There were in fact a number of small offsets (of both sign) between the same stations in the two different data sets. The obvious fix was to make an adjustment based on a period of overlap so that these offsets disappear."