Tuesday, August 18, 2015

USHCN again - adjustments breakdown

There is another post at WUWT based on Steven Goddard's discredited plots of USHCN adjustments. I dealt with that in detail here. What Goddard does is to calculate the effect of adjustment by taking the difference of one set of stations, adjusted, and a different set (a subset) unadjusted. But of course, the difference includes the climatic differences between the disparate station sets, which are not a result of adjustment. And I show there that that dominates, by simply repeating the calc with long term means replacing the monthly data for the non-overlapping part. The result is very similar, showing that the difference is not due to adjustment, or even weather, but to the different climate mix of the stations.

Prof RG Brown was the promoter of the SG graph at WUWT, but he didn't seem to have much interest in where it came from. I think there is still no link to the Goddard source article (which tells nothing anyway). But I can use one of his analogies to describe why the SG approach is all wrong. RGB postulates a process where the growth of young trees is quantified by measuring total height with a tape measure. So, suppose you measured 5 trees with a tape, and 5 other trees with a ruler. You suspect that the tape may be biased high. So you subtract the mean of the two sets of 5, and say that is the difference due to the tape vs ruler.

But of course it isn't. There is no control to say that the tree heights match. The average heights would be different even if all measured with the same measure. OK, in the USHCN the raw stations were a subset of the adjusted, so a closer analogy would be having all 10 measured with tape, and a subset of 5 with ruler. You still can't quantify the ruler/tape by just differencing means of 10 and 5.

Anyway, SG posted a response here. It is worthless, because he won't let go of the nonsense calc. He disputes my observation that TOBS is a major part by showing two graphs, both with his nonsense component. Yes, of course that is then indeed dominant. Most ridiculously, he says:
"Nick also claims that I am comparing two different sets of stations. This is complete BS. USHCN fabricates missing data for almost half their stations. That is an utterly unacceptable practice."
That is a complete non-sequitur. The stations are different places. Whether he thinks they shouldn't be is irrelevant.

A while ago, to counter some other clumsy mis-calcs of USHCN, I posted a breakdown of USHCN adjustments by state. I'll repeat this below the fold showing separately, as NOAA does in its data, the part due to TOBS, the other adjustment (mainly homogenisation), and the total. TOBS is the biggest, and it is the part with a consistent uptrend, for well-established reasons set out here.

Meanwhile, over a year ago, NOAA rolled out its new nClimDiv system, which really makes all this obsolete.

In these plots, the total adjustment is marked in red. Blue is the part due to TOBS, and green is the remainder. You can click on any state abbreviation below the plot to bring up that state's data. Details of the averaging etc is here. You can see that for the USA in total, while the adjustment reaches about 0.9°F, the maximum difference for the non-TOBS component is less than 0.4°F.

ps. This calc solves (mostly) an earlier puzzle that the present day adjustment is not zero, as would normally be expected. The discrepancy is mostly in the TOBS component. I suspect that the TOBS adjustment has been set to correspond to a midnight reading, as most MMTS is nowadays. So the few remaining min/max thermometers are adjusted accordingly, even to present. Well, it's a theory.

Update - methods

Methods are as for the earlier post. Each point plotted is an average of differences for stations. This means that only stations with raw data are included. State averages are unweighted, but the national average is weighted by state area. The code to produce these plots is similar to that posted earlier, and is here


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