More on NASA Correcting Their Temperature Data

Over at DailyTech:

My earlier column this week detailed the work of a volunteer team to assess problems with US temperature data used for climate modeling. One of these people is Steve McIntyre, who operates the site climateaudit.org. While inspecting historical temperature graphs, he noticed a strange discontinuity, or "jump" in many locations, all occurring around the time of January, 2000.

These graphs were created by NASA's Reto Ruedy and James Hansen (who shot to fame when he accused the administration of trying to censor his views on climate change). Hansen refused to provide McKintyre with the algorithm used to generate graph data, so McKintyre reverse-engineered it. The result appeared to be a Y2K bug in the handling of the raw data.

McKintyre notified the pair of the bug; Ruedy replied and acknowledged the problem as an "oversight" that would be fixed in the next data refresh.

NASA has now silently released corrected figures, and the changes are truly astounding. The warmest year on record is now 1934. 1998 (long trumpeted by the media as record-breaking) moves to second place. 1921 takes third. In fact, 5 of the 10 warmest years on record now all occur before World War II. Anthony Watts has put the new data in chart form, along with a more detailed summary of the events.

The effect of the correction on global temperatures is minor (some 1-2% less warming than originally thought), but the effect on the U.S. global warming propaganda machine could be huge.

It does make you wonder--if the figures for the U.S. were wrong, how confident are we in the data from other countries used by the global warming true believers?

UPDATE: A reader points to this data set, which appears to be the "before."