After a Toronto skeptic tipped NASA this month to one flaw in its climate calculations, the U.S. agency ordered a full data review.
Days later, it put out a revised list of all-time hottest years. The Dust Bowl year of 1934 now ranks as hottest ever in the U.S. – not 1998.
More significantly, the agency reduced the mean U.S. "temperature anomalies" for the years 2000 to 2006 by 0.15 degrees Celsius.
NASA officials have dismissed the changes as trivial. Even the Canadian who spotted the original flaw says the revisions are "not necessarily material to climate policy."
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."
A former mining executive who runs the blog ClimateAudit.org, McIntyre, 59, earned attention in 2003 when he put out data challenging the so-called "hockey stick" graph depicting a spike in global temperatures.
This time, he sifted NASA’s use of temperature anomalies, which measure how much warmer or colder a place is at a given time compared with its 30-year average.
Puzzled by a bizarre "jump" in the U.S. anomalies from 1999 to 2000, McIntyre discovered the data after 1999 wasn’t being fractionally adjusted to allow for the times of day that readings were taken or the locations of the monitoring stations.
McIntyre emailed his finding to NASA’s Goddard Institute, triggering the data review.
"They moved pretty fast on this," McIntyre said. "There must have been some long faces."