Despite the fact that NASA tried to block him from accessing U.S. temperature data, persistent efforts by a climate change blogger forced the government to amend U.S. temperature data.

Because of the blogger’s efforts, NASA now recognizes 1934 as the hottest year in U.S. history, not 1998.

Steven McIntyre, a former mineral exploration executive and policy analyst for the governments of Ontario and Canada who blogs at ClimateAudit.org, wrote to NASA on August 4. He had found miscalculations in the NASA’s U.S. temperature recordings made after January 2000. “For Detroit Lakes, Minnesota,” McIntyre wrote “this introduced an error of 0.8 deg C.”

NASA responded on August 7 to tell McIntyre data was “changed correspondingly with an acknowledgement of your contribution.” Without any fanfare, the changes were made on the NASA website. The recalculations resulted in an overall decrease in U.S. temperatures since 2000 by 0.15 degrees centigrade. In a phone interview McIntyre said, “That doesn’t necessarily seem that much, but when the entire increase in temperature in the United States had been previously reported to be about half a degree, this .15 degree is not a small number when you are measuring half degree numbers.”

Now, the ten hottest years on record in the U.S., beginning with the hottest year, are: 1934, 1998, 1921, 2006, 1931, 1999, 1953, 1990, 1938 and 1939. Before the revision, that list read: 1998, 1934, 2006, 1921, 1931, 1999, 1953, 2001, 1990 and 1938. The re-ranking completely knocked 2001 off the top 10 list.

This U.S. temperature revision could cause problems for former Vice President Al Gore. Assisted by Hansen, Gore asserted in his global warming film “An Inconvenient Truth” that nine of the ten hottest years in U.S. history occurred since 1995.

McIntyre said he began looking at the data because he questioned the reliability of NASA’s U.S. weather stations that recorded temperature data. He said, “Some of them were in places they weren’t supposed to be….one of them was in a parking lot and the trend for the station in a parking lot was way up and a nearby station that was in a proper location in a rural area was relatively flat.”

Chris Horner, author of The Politically Incorrect Guide to Global Warming and Environmentalism, said McIntyre was able to catch the mistake because he “knew that our surface measuring stations are suspect.” Horner said the polling stations could be affected by things like the construction nearby asphalt parking lots, tar roofs, AC vents, chimneys, or even a grill restaurant.

McIntyre said, “Defenders of the weather station system argued that NASA had software that could fix that data…And, so I wrote to NASA in May and asked them for the source code for the adjustment software that they used to fix these stations and they refused to provide it.”

But, “the adjustments are not small,” McIntyre said. “The adjustments that they make are fully equal the total amount of warming in the United States the past century.”

According to McIntyre, when he began downloading data from NASA’s website to compare the adjusted and the raw data from the polling stations, “this led to a bit of a fight with NASA in May. As I started downloading the data in sequence they cut off my access to the data.”

“They blocked my IP address,” McIntyre said.

When contacted by phone to verify the computer block NASA spokeswoman Leslie McCarthy said, “This is the first I’ve heard of this.” McCarthy had not yet responded to the full transcript at the time of publication.

“After I was blocked and I explained myself they still didn’t want to let me have access to the data,” McIntyre lamented.

He continued: “They just said go look at the original data. And I said no, I want to see the data you used. I know what the original data looks like. I want to see the data that you used. But one of the nice things about having a blog that gets a million and half hits a month is that I then was able to publicize this block in real-time and they very quickly withdrew their position and allowed me to have access.”

When he got the data, McIntyre then compared the raw and adjusted data sets for all 1200 U.S. weather stations. “Probably 75 percent of the stations had jumps of at least a quarter degree in the year 2000,” he said.

Conservative media personalities like talk radio host Rush Limbaugh and blogger Michelle Malkin blasted the revision that was made quietly.

The Director of NASA’s Goddard Institute for Space Studies James Hansen responded to the critics on the left-wing blog DailyKos. He said that U.S. temperature data change is inconsequential to overall global climate data.. He wrote a diary on their site on August 11 that said, “The effect on global temperature was of order one-thousandth of a degree, so the corrected and uncorrected curves [on global data] are indistinguishable.”

Jeff Kuerter, president of the George C. Marshall Institute, said NASA’s mistake cast doubt on all global climate data because the United States was considered the best at taking analyzing temperatures. “If the U.S. doesn’t get this right what might be happening in other places and why did this error persist so long?” he said.

In an August 13 Newsweek cover story, “The Truth About Denial,” Kuerter’s organization was labeled as part of the “denial machine” in cahoots with Exxon Mobil and the American Petroleum Institute.

Exxon Mobil spokesman Gantt Walton said Exxon had no comment regarding NASA’s climate change revisions.

Even though the data has been corrected, McIntyre is not satisfied. “They claim that they’re adjustment methodology was capable of fixing bad data, I mean, that’s the point I want people to take home from this,” he said. “What they’ve done now is inserted a patch into an error that I identified for them but they haven’t established that the rest of their adjustment methodology is any good.” He recommended that NASA begin archiving the codes they use to make calculations and subject data to public scrutiny or peer-review.

This isn’t the first time McIntyre has caused a stir by questioning global warming data. The Toronto-based McIntyre joined forces with Canadian economist Ross McKitrick to refute data put forth by United Nations in 2001 that said use of fossil fuels was causing global warming. Included in the report was a graphic that showed 20th century temperatures sharply rising as time went on in the form of a hockey stick, which later became the name of the graph. McIntyre and McKitrick found an error in the mathematical calculation used to construct the “hockey stick.” Their findings led to a congressional investigation led by then-chairman of the House Energy and Commerce Committee Rep. Joe Barton (R.-Tex.).

Below is Carpenter’s transcript of her interview with Steven McIntyre:

Q. Can you explain to me in layman’s terms how you found this error?

Yeah. Quickly, a fellow in California named Anthony Watts noticed that some of the weather stations used to make historical U.S. statistics were located in places they weren’t supposed to be. One of them was in a parking lot and the trend for the station in a parking lot was way up and a nearby station that was in a proper location in a rural area was relatively flat. So, this led to some controversy and he started a volunteer effort where people started surveying these weather stations and seeing what they looked like.

Now, defenders of the weather station system argued that NASA had software that could fix that data. And, so it really didn’t matter if the station was in a parking lot in Tuscan or something like that. NASA software could fix it. So, that type of adjustment is a statistical issue that interests me. And, so I wrote to NASA in May and asked them for the source code for the adjustment software that they used to fix these stations and they refused to provide it. So I got interested in sort of looking at comparing the version of the temperature history of individual stations that NASA had against original data. I noticed that in some cases there was a very sharp jump in the differences between these two versions. The NASA version took a step in January 2000 relative to the original data. So, I then collected the data for both the NASA versions and the original data for all 1200 stages in the US historical network.

This led to a bit of fight with NASA in May because as I started downloading the data in sequence they cut off my access to the data.

Q. Meaning, your computer? Continued...