Wednesday, August 19, 2015

USHCN adjustments - a case study

In my last post, I linked to a post at Steve Goddard's, grumbling about my comments at WUWT, where I linked to my earlier post showing a breakdown of total adjustment by states. A commenter picked up on New Hampshire, saying
"I particularly like nick’s new hampshire graph with a whole degree warming suddenly applied a few years ago. Their actual temps were obviously not cooperating."

Well, there is indeed a steep rise at about 1991:

The new graph shows that in 1991-2 there was a total rise of about 1°F made up about equally of a TOBS rise and a non-TOBS part. How could that happen? I investigated.

New Hampshire has just 5 USHCN stations, all operating to end 2013, at least. They are Bethlehem, Durham, First Connecticut Lake, Hanover and Keene. It turns out that the first and last underwent big changes about 1991-2. You can look up the relevant metadata here. Location is under the station-level tab, or location tab (map). TOBS is element level.

Bethlehem is actually a composite. The map below shows what happened. B1 lasted to 1 Jan 1992, and then reappeared as B2 about 4 km NE on 1 Jul 1992. Altitude dropped from 1380 ft to 1180 ft, or about 60 m, which would suggest about 0.7F rise in temp. However, the move also took the station out of town, and the cooling effect of that seems to have dominated.

But at the same time, the time of observation moved from 17.00 (warm bias) to 07.00 (cool). That would require an upward adjustment of order 1-2°F.

The total observed rise in adjustment for Bethlehem was 2.46°F, made up of 1.04 TOBS and 1.42 other.

For Keene, the relocation happened 28 Jan 91, and is recorded as moving 2.9 mi NW. Elevation rose 30 ft, but again, it was a move out of town. And again, the TOB changed from 17.00 to 7.00, requiring a warm adjustment.

The total rise for Keene was 3.34°F, made up of 2°F TOBS, and 1.34F other.

So the combined rise was 5.8°F, which divided by 5 in averaging gives indeed the observed NH rise in adjustment of 1.16°F.


  1. The typical size of an abrupt inhomogeneity (break) is 0.6 to 0.8°C.

    More formally, the distribution of breaks is well approximated by a normal distribution with a sigma of about 0.6 to 0.8°C.

    In Europe the sizes may be a little larger than in the USA, in return the USA seems to have a somewhat higher frequency of breaks.

    1. Yes. the two breaks here are .74°C and .79°C, after TOBS is applied first.

  2. Congrats on managing to maintain a debate of sorts with Steven/Tony. I get the impression he's actually accepting that TOBs adjustments might be justified - something of a turn-around from his position that in times past the people managing weather stations would not have been such "morons" (as SG delights in labelling people) as to actually follow the protocol they were given to always take max and min temperatures at the stipulated times of day. That said, he also seems to be adopting a new position that TOBs constitute a relatively small part of the adjustments - though his own plots would suggest otherwise.

    Still, maybe there is some "reconciliation" between two Lisbon-2011 veterans here. I might recommend this thread to Jerry Ravetz.

    1. Well, Bill, re TOBS I thought that the SG line was still that they should have just made up a policy as they go along to catch the daily max/min. The fact that they didn't as irrelevant as the need to stick to a schedule.

      Once you insist that any adjustment is a fabrication and fraud, you just can't make progress. There is nothing to talk about.