During the “Political Grapevine” segment of the August 10 edition of Fox News' Special Report with Brit Hume, guest host and chief Washington correspondent Jim Angle reported that NASA was forced “to admit it was wrong when it said that 1998 was the hottest year on record” and that NASA “now says 1934 was the hottest year, followed by 1998, then 1921.” But Angle did not inform viewers that NASA's revision affected annual temperature rankings for the United States only; it had no effect on the annual global temperature rankings. According to NASA climate modeler Gavin A. Schmidt, 2005 remains the warmest year globally in the instrumental record, followed by 1998.

Angle further stated that “five of the hottest 10 years on record occurred before World War II.” In fact, this statement is true only for temperatures in the United States; according to NASA, all 10 of the warmest years globally in the instrumental record have occurred after 1989.

Angle's report was accompanied by an on-screen graphic reading: “1998 Not So Hot.”

From the August 10 report:

ANGLE: The man behind the website climateaudit.org has forced NASA to admit it was wrong when it said that 1998 was the hottest year on record. Steve McIntyre had to reverse-engineer NASA's figures because the agency refused to give him the formula it used to make the claim. And McIntyre found out NASA had made a serious mistake. NASA eventually agreed and now says 1934 was the hottest year, followed by 1998, then 1921. In fact, five of the hottest 10 years on record occurred before World War II.

NASA recently corrected its climate figures after the discovery of inconsistencies in its U.S. temperature data. According to Schmidt, a climate modeler at NASA's Goddard Institute for Space Studies and a contributor to the RealClimate blog (posting as “gavin”), the correction resulted in a re-ranking of NASA's list of the warmest years in the United States. For example, whereas 1998 was previously ranked as the warmest year for the United States, it is now ranked second, behind 1934. According to Schmidt, the temperature difference between 1934 and 1998 in the United States -- both before and after the correction -- is not statistically significant.

According to Schmidt, the effects of the correction on annual global and hemispheric temperature data are “imperceptible”:

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.

This was duly done by Tuesday, an email thanking McIntyre was sent and the data analysis (which had been due in any case for the processing of the July numbers) was updated accordingly along with an acknowledgment to McIntyre and update of the methodology.

The net effect of the change was to reduce mean US anomalies by about 0.15 ºC for the years 2000-2006. There were some very minor knock on effects in earlier years due to the GISTEMP adjustments for rural vs. urban trends. In the global or hemispheric mean, the differences were imperceptible (since the US is only a small fraction of the global area).

There were however some very minor re-arrangements in the various rankings (see data). Specifically, where 1998 (1.24 ºC anomaly compared to 1951-1980) had previously just beaten out 1934 (1.23 ºC) for the top US year, it now just misses: 1934 1.25ºC vs. 1998 1.23ºC. None of these differences are statistically significant.

[...]

More importantly for climate purposes, the longer term US averages have not changed rank. 2002-2006 (at 0.66 ºC) is still warmer than 1930-1934 (0.63 ºC - the largest value in the early part of the century) (though both are below 1998-2002 at 0.79 ºC). (The previous version - up to 2005 - can be seen here).

In the global mean, 2005 remains the warmest (as in the NCDC analysis).