Too little attention has been given to the news last August that NASA had made a year-2000 mistake in calculating US temperatures, a mistake that meant the temperatures after 2000 were all too high. Details are at Coyote Blog
. The mistake was in the adjustment NASA makes for the fact that if a weather station's location become urban, the temperature rises because cities are always hotter.
What is more important than the mistake itself are that
(1) NASA very quietly fixed its data without any indication to users that it had been wrong earlier.
(2) NASA's adjustment is by a secret method it refuses to disclose to outsiders.
(3) NASA's adjustment appears (hard to say since it's kept secret) to both adjust "bad" stations (the ones in cities) down and "good" stations (the ones that read accurately) up, on the excuse of some kind of smoothing of off-trend stations.
(4) The NASA people doing the adjustment are not statisticians.
(5) It isn't clear what, if any, adjustment is made to weather station data from elsewhere in the world. The US has some of the best data, and there seems to be no warming trend in the US.
Labels: global warming, statistics