Eli Rabett and Tamino have both advocated faith-based climate science in respect to USHCN and GISS adjustments. They say that the climate “professionals” know what they’re doing; yes, there are problems with siting and many sites do not meet even minimal compliance standards, but Hansen’s software is able to “fix” the defects in the surface sites. “Faith-based” because they do not believe that Hansen has any obligation to provide anything other than a cursory description of his software or, for that matter, the software itself. But if they are working with data that includes known bad data, then critical examination of the adjustment software becomes integral to the integrity of the record – as there is obviously little integrity in much of the raw data.
Eli Rabett has recently discussed the Detroit Lakes MN series as an example where the GISS adjusted software has supposedly triumphed over adversity and recovered signal from noise. And yet this same series displays a Hansen adjustment that will should leave anyone “gobsmacked”.
I’ve referred to Hansen’s Y2K problem in passing before, but it’s interesting to see it in a particularly loud form in the series cited by Rabett as an adjustment triumph. (By Y2K problem here, I don’t specifically mean that the error is due to 2-digit date formats, but that the error, whatever its source, is observed commencing Jan 2000.)
The first three panels of the figure compare the GISS raw version to three USHCN versions: “raw”, time-of-observation adjusted (TOBS) and adjusted (filnet). In 1951, the Detroit Lakes station moved from the back yards of DL 2.1 NNE to KDLM radio station. For the period 1951-1999, the GISS raw version is virtually identical to the USHCN adjusted version (which in turn is virtually equal to the TOBS version.)
But look at what happens in 2000. The input version at GISS switches from the USHCN adjusted/TOBS version to the USHCN raw version (without time-of-observation adjustment). This imparts an upward discontinuity of a deg C in wintertime and 0.8 deg C annually. I checked the monthly data and determined that the discontinuity occurred on January 2000 – and, to that extent, appears to be a Y2K problem. I presume that this is a programming error.
The plot also shows a substantial difference between GISS raw and any of the USHCN versions prior to 1951. I don’t know what the explanation for this is right now. However the effect of this difference is to enhance the difference between recent and 1930s values in the GISS raw version. This difference is slightly attenuated by the GISS “UHI” adjustment.
This is not to say that increases in Minnesota temperatures are entirely due to Hansen’s Y2K error. Post-1999 values at Detroit Lakes are high without Hansen’s error. However, Hansen’s error here is still a large one – being equal in size to the entire estimated amount of global warming in the past century. This is also not to say that this error is what “causes” temperature increases in Hansen’s data. I’ve noticed this error in sites where there was a negative TOBS adjustment as of 2000 (Grand Canyon was another example). Many sites do not have a TOBS adjustment at 2000 and are unaffected. However Detroit Lakes seems like rather a poor choice as a type case demonstrating the triumph of GISS adjustments, as it contains a relatively obvious error that appears to be little more than a programming error.