As a reader at Anthony’s blog notes, there’s an interesting history here.
Note that the temperature graphic shown linked at Anthony’s site is the version used by NOAA, rather than the version used by NASA. The differences are shown in the two graphs below. The NASA adjusted version increases past L.A. temperatures by an amount increasing linearly to about 1.2 deg C, while NOAA uses a version without NASA’s urban adjustment.
While NASA’s U.S. temperature history shows warm 1930s, with 1934 vying with 1998 as warmest year of the century, NOAA, under the direction of Tom Karl, makes no corresponding effort to adjust for urbanization.
Anthony, Atmoz and ourselves have recently discussed the ineffectiveness of the NOAA Filnet adjustment to detect station changes (see Lampasas and other sites). Here we have another example of exactly how ineffective this algorithm is. Neither NOAA nor NASA pick up the re-location of the Los Angeles station (which in this case appears to result in a decrease in temperature. Both NOAA and NASA GISS failed to pick up and adjust for the re-location even though two NASA employees published an article on the relocation in an article published on the NASA website here: http://www.jpl.nasa.gov/news/features-print.cfm?feature=1273 stating:
The magnitude of change reflected in our study strongly suggests this relocation will bias long-term climatic studies.
So it’s not just Anthony Watts who’s observed that station re-locations can bias climatic studies. As we’ve observed previously, climate scientists seem much better at detecting discontinuities with downward biases (such as the most recent L.A. move) than ones with upward biases, such as Lampasas or the Y2K error.