13 August, 2007

The politics of data manipulation

Ken Holder points us to this little gem of a discovery:



Years of bad data corrected; 1998 no longer the warmest year on record


An example of the Y2K discontinuity in action [. . .] this week detailed the work of a volunteer team to assess problems with US temperature data used for climate modeling. [. . .] 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.



Links in the original article. Emphasis mine.

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