An amateur meteorologist in Canada has embarrassed NASA scientists into admitting that some of the data they used to show significant recent increases in global warming is flawed.
As a result of Stephen McIntyre's calculations, climatologists at the Goddard Institute of Space Science in New York now accept that 1934 was historically the US' hottest year since records began, not 1998 as they had claimed.
It also turns out that five of the 10 warmest years on record in the US occurred before 1939, and only one is from the 21st century, raising questions over the statistics used in former US vice president Al Gore's environmental film An Inconvenient Truth to highlight the faster pace of climate change.
"They have managed it rather poorly," said McIntyre, a prolific Internet blogger from Toronto who pointed out the gaffe to NASA in an e-mail.
He noticed that temperature deviation readings from numerous weather-recording stations around the US showed sudden and inexplicable leaps after 2000.
He said the agency refused to share with him the complex methodology it used to calculate trends from the data, then quietly changed statistics to rewrite history without explanation.
"They [NASA] might not like the fact they made a small embarrassing error, but if it were me I'd have announced the results and put the best spin on it that I could. I would not have left myself open to the suggestion that I was not being forthcoming," McIntyre said.
Climate researchers at the Goddard center, meanwhile, say McIntyre is making a mountain out of a molehill and that the differences in the recalculated temperatures, hundredths of one degree, are so insignificant as to have no impact on the overall trend toward global warming.
The cause of the error, they say, was a switch to a new data-collection system in 2000 and a faulty assumption that the old and new methods matched, which last week led to a recalculation of the figures.